NITROXDIVER

MANUAL

© ESA WorldWide

No part of this book may be reproduced in any formProduct n° M0011

Editor: Mauro Bertolini

Formative project, development, consulting and revision:Mauro Bertolini, Mario Romor, Miho Tsuruoka, EgidioTrainito, Maria Laura Careddu

Text and photos: Mario Romor

Illustrations: Stefano Trainito, Jacopo Pasqualotto

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Index

Chapter OneNew chances

7 What will You learn?7 Nitrox8 Definitions

10 Calculations14 Planning20 Diving21 Analysing O2 24 Congratulation!25 What have You learn?

Chapter Two 26 What will you learn?26 Miscellaneous 30 Equipment33 Recharging35 Oxigen37 CNS oxygen clock40 Managing emergencies42 Congratulation!43 What have You learn?

Chapter Three47 Open Water dives 1 and 251 9 rules for diving with Nitrox

Appendix52 ESA54 9 Suggestions to preserve the aquatic environment55 Not to be left at home56 NOAA dive table of O2 exposition and conversion tables57 Formulas58 ESA EAN 36 – EAN 32 – AIR DIVE TABLES60 O2 analisys

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Chapter OneNew chances

It ’s a beautiful day, the sky is clear, the sea iscalm and the temperature is warmoutside and in the water as well.These are the perfect conditions todive on the KT, one of the most inte-resting and well kept wrecks of theMediterranean Sea.

Karen and Denise, two ESA WreckDiver licensed divers, are enthu-siast: the good weather conditionsand the favourable sea state letthem have a great dive, and now,back on the boat, they are discus-sing it with Robert, the Diveleaderwho escorted them. One only regret:“It’s a pity the dive was so short!”

Several minutes later, while thethree divers are still talking, ano-ther group of divers emerge. Theyare guided by Lucy, the otherDiveleader that works at the divingcentre. After the divers are onboard,Karen asks Lucy why they dived forlonger and if a decompress stop wasneeded. Lucy explains that, according to therules of the diving centre, divesexceeding the no decompressionlimits are forbidden, and that sheand the other divers could stay lon-ger because they used a gas mixsimilar to air, but with less nitrogenand more oxygen: Nitrox.

Karen and Denise, happy for chanceto dive longer, ask Robert to useNitrox during the second dive, so that they couldvisit the bow of the boat, that is surrounded bymany fish such as corvinas and groopers.Robert tells them that is not possible to dive withNitrox because there are not enough cylindersand they need to be trained to use it.

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Needless to say that, after noting that they mustfinish their second dive before than the otherdivers that are using Nitrox, the two friends deci-de go get informed the ESA Nitrox Diver course.Getting the ESA Nitrox Diver license is reallyeasy; this manual and your ESA Nitrox DiverInstructor will provide all the information neededto diver longer without exceeding the no decom-pression limits, using properly the two most com-mon Nitrox mixes: NOAA Nitrox 1 and NOAANitrox 2 (i.e. Nitrox with 32% and 36% of oxygenrespectively).

You will learn to analyse the gas mix what youwill use, to plan your dives and to monitor expo-sure to oxygen.

During your course the ESA Nitrox DiverInstructor will show how to perform all neededactions and will give suggestions on the bestusage of the “hyper-oxygenated” gas mixes, inorder to take advantages from their potentialityavoiding any potential problems.

Read and answer the questions you find in the“miniquiz” and the “What have you learned?”questionnaires, start this new adventure and addyour new important license to your collection.

The ESA Nitrox Diver license enables you torecharge and hire Nitrox cylinders, dive withNitrox and satisfy the need to have it as a prere-quisite for other courses.This manual deals with the new limits establis-hed for recreational dives with Nitrox; anyhow,your new license does not authorize you to gobeyond the limits of your main license. Forinstance, the limits for an ESA Open Water Diver(or similar license released from other organisa-tions) is 18 metres without exceeding the nodecompression limits. If you have not done it already, in order to betteruse the potentiality if Nitrox, you may think toattend the ESA Advanced Diver course, in orderto extend your depth limit to 30 metres, alwayswithin the no decompression limits.

The ESA Nitrox Diver program can be carried outduring other courses, such as ESA Open WaterDiver and ESA Advanced Diver; ask your instruc-

The mostgreater timegranted bythe Nitroxallows amore accu-rate explora-tion

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tor what you need to do to get the two licensesduring two integrated training programs.

What will you learn?Knowing the composition of Nitrox, its effects,how planning dives correctly and getting readyfor them makes the divers fully use the potentia-lities of hyper-oxygenated gas mixes (or withreduced amount of nitrogen) without exposingthemselves to risks.What is Nitrox? What are the associated risks?What do I need to do to plan dives with Nitrox?How can I prepare my dive at the best? Howshould I behave while diving? How will I analyzethe gas mix and check the oxygen percentage?You will find the answers to the above and otherquestions in this chapter. The information youwill get will be useful already during the firstdive; should you have any doubts or additionalquestions, don’t hesitate to ask your ESA NitroxDiver Instructor.

NitroxThe word Nitrox is com-posed by two words:nitrogen and oxygen,the two main gassesthat constitute the airyou breath everyday.The air can be conside-red to be a Nitrox mixwith 21% of oxygen,that is the “normal”percentage of oxygencontained in the air.Such a mix, with 21% ofoxygen and 79% ofnitrogen is called air,while the word “Nitrox”is specially used to indi-cate an oxygen enri-ched air mix. By Nitroxwe intend all thosebreathable mixes with more oxygen and lessnitrogen.You can easily understand that, in order to main-tain the overall equilibrium and pressure of agiven amount of air, you need to increase thequantity of oxygen when reducing the amount ofnitrogen.

The Nitroxcertifica-tion thatyou willreceive isessential toparticipateto immer-sions withthe Nitrox

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How does it happen? You will find the answer inthe next chapter which deals with preparation ofNitrox. Please note that Nitrox can be preparedby qualified people only.Any mix containing a percentage of oxygen higherthan 21% can be called Nitrox or Enriched Air; theoxygen percentage in mixes used for recreationaldives ranges between 21% and 40%. For safetyand practical reasons, the ESA Nitrox Diver coursedeals mainly with the two most tested, diffusedand convenient ones: NOAA Nitrox I e NOAANitrox II, containing 32% and 36% of oxygenrespectively.

In specific dives such as technical, military, explo-rative, scientific or during which people workunder water, Nitrox mixes with oxygen percentagehigher than 40% can be used; this is to reduce thedecompression time. The ESA Nitrox Diver courseis for divers who want to extend the no decom-pression limits respecting all safety margins.Therefore, this manual does not treat any of thespecific dives listed herabove.

DefinitionsTo avoid confusion and use the potentiality givenby Nitrox to the maximum extent, some defini-tions are needed. It may looks like things getmore complex at the beginning, but you will beable to remember them easily.Let’s start from the two main gasses: as you mayalready know, O2 is the symbol for oxygen and N2is that for nitrogen.Many divers refer to Nitrox calling it EANx, thatis Enriched Air Nitrox, where “x” indicates theoxygen percentage. EAN 32 and EAN 36 are thetwo “standard” mixes and are equivalent to enri-ched air with 32% of O2 (the former) and 36% ofO2 (the latter).The National Atmospheric and OceanicAdministration (NOAA), is an US organisationinvolved in many subjects, mainly for commercialreasons.Its field of application ranges from dives on ocea-nic sea bed to aerospace; it published the diveplanner with two Nitrox mixes mentioned abovein the seventies.The person who standardised the two mixes wasDoctor Morgan Wells, who is know for havingmanaged the “Nitrox” program at NOAA. The

Minitest1. True or FalseThe gas mixture prepara-tion must be performed byrecreative divers.

2. The word Nitrox iscomposed from thenames of:a. Nitrogen and oxygenb. Oxygen and dioxide ofcarbon c. Nitrogen and helium

3. The denominatedmixture NOAA Nitrox 1are essentially compo-sed from:a. 21 % oxygen and 79%nitrogen b. 32% oxygen and 68%nitrogenc. 36% oxygen and 64%nitrogen

Answer:1 False, 2 a; 3 b.

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standardisation was needed to optimise the useof Nitrox having regards to the maximum level ofsafety.It is thanks to his colleague, Dick Rutkowksi, thatNitrox started to be used in sportive dives in theeighties and, subsequently, in the recreationaldives.

It will happen that you will listen about “de-azoti-sed air”; this is due to the fact that you can pro-duce Nitrox by subtracting nitrogen from air.Indeed, we can refer to Nitrox also in relation tothe fact that the percentage of nitrogen is redu-ced instead of talking about the higher quantityof oxygen. Anyhow, considering the effect thatthe latter has while diving, the Nitrox mixes aredefined on the base of the quantity of oxygenthey contain.

Gas percentages are often called “fraction of agas” (Fg); for instance, fraction of O2 (or FO2 )that indicates the quantity of oxygen, andFraction N2 (or FN2) for nitrogen. Rememberthat by subtracting FO2 to 100 youcalculate FN2.

The effect of a gas on the organismis dependent upon its partial pres-sure, usually indicated with pp orPg. For instance, PO2 indicates theoxygen partial pressure and PN2the nitrogen one.At sea level, where the ambientpressure is 1 BAR or 1 ATM, youcan easi ly calculate the partialpressure of the two gasses: it is the21% of 1 BAR for oxygen (0,21 BAR)and 79% of 1 BAR for nitrogen(0,79 BAR). You will have alreadynoted that 0,21 + 0,79 = 1.The next paragraph will teach youto process other mathematicaloperations related to dives withNitrox.As already done for the ESA Open Water Divercourse, the pressure is indicated in BAR, that cor-responds to 1 atmosphere or 14,7 PSI.ATA indicates absolute pressure, that is theambient pressure, that is calculated adding 1 BAR(the atmospheric pressure) to the hydrostatic

Alwaysaddress to aspecializedcenter

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pressure (1 BAR every 10 metres of salt water).

CalculationsUsually mathematics helps solving problems, dis-covering new things and, during your ESA OpenDiver course, to calculate how the pressure chan-ges with depth. Furthermore, the dive plannerare based upon mathematical calculations. Onceagain, mathematics will help you in understan-ding principles and plan dives with Nitrox, maxi-mising amusement and making sure safety is fullyguaranteed.Planning dives is one of the most important acti-vities when you use Nitrox. Planning has a funda-mental role for safety and to better use thepotentiality offered by Nitrox.

You have already learned to plan dives with airduring your diving courses. Planning dives withNitrox is based on the same steps and care, but,in addition to this, you need to take in dueaccount the different gas percentages. While asmaller quantity of nitrogen extend the nodecompression limits, the higher quantity of oxy-gen reduces the maximum depth you can reachand increases the exposition to oxygen rate.Furthermore, in relation to the breathed gas, youwill have to take into consideration the equip-ment you use (more information will follow in thenext chapter).

Extended no decompression limits imply a longerdive, for which you must consider Nitrox con-sumption (breathing) and temperature of thewater (you may be cold).How can you calculate the extended no decom-pression limits when using Nitrox? You will usedive planners similar to those used for air, thattakes into account the reduced quantity of nitro-gen; you can also use special computers specifi-cally designed to dive with Nitrox.You can use the “ESA Dive Tables” for air and findthe no decompression limits using the EquivalentAir Depth (EAD) defined shortly, or the ESA “EAN36 - EAN 32 - Air Dive Tables”, specifically desi-gned to plan dives with the most diffused Nitroxmixes and, if needed, with air.

Just like the ESA “Dive Tables”, the ESA “EAN 36 -EAN 32-Air Dive Tables” contains three table that

Minitest1. EANx initials it is used forpointing out:a. Enriched Air Nitroxb. Air Enriched of Oxygen c. a and b are exact

2. The term "air nitrogenfree" :a. It is reported to the factthat Nitrox can be produ-ced escaping nitrogen fromthe air b. It is to point out a mixtu-re with high nitrogen con-centrationc. It points out a composedspecific mixture of 80% ofoxygen and 20% of nitro-gen

3. The sigles pp and Pgpoint out:a. The percentage of oxy-gen b. The nitrogen percentagec. The partial pressure of adatum gas

Answers:1 c; 2 a; 3 c.

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enables you to plan single dives and provide pres-sure groups after the dive (EANx Table 1), find thenew pressure group after a specific surface inter-val (EANx Table 2) and plan the repetitive dive(EANx Table 3).The ESA EANx Table 1 includes three columns forEAN36, EAN32 and AIR respectively. The threecolumns show the actual depths related to eachspecific mix; using this table you don’t need tocalculate the EAD to plan you dives.

What is the EAD? To answer this questions, let’srefresh the partial pressure of gasses. As you will remember, the effect of a gas on theorganism is dependentupon its partial pressu-re. During your ESAOpen Water Diver cour-se you learned that asmall quantity of car-bon monoxide may betolerable at the sealevel but can be toxicunder water because ofits increasing partialpressure.

The effects of nitrogenare due to its partialpressure; for this rea-son, nitrogen narcosisand nitrogen absorp-tion increase withdepth.It is easy to understand that the higher the nitro-gen partial pressure, the smaller the no decom-pression limits; there are to ways of increasingthem, or reducing the nitrogen narcotic effect: 1)reducing depth and, therefore, the nitrogen par-tial pressure; 2) reducing the quantity of nitrogenin the gas mix, so that, at the same depth, thepartial pressure is less.For instance, the quantity of nitrogen in an aircylinder breathed at 20 metres as a partial pres-sure of 2,37 BAR (0,79 BAR x 3 ATA), while theppN2 for the EAN36, at the same depth is 1,92BAR (F N2 x ATA at 20 metres salt water = 0,64bar x 3 bar =1,92 bar).

As you can see, the two partial pressures are sub-

1The ESANitrox Divetable usedfor Nitrox36 and 32point outin 120minutesthe maxi-mum timeof singleimmersion

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stantially different: 2,37 BAR vs 1,92 BAR; thediver who breaths Nitrox absorbs the sameamount of nitrogen of a diver that breaths air atthe same depth in a longer time.

When you breath Nitrox at a given depth it is as ifyou were breathing air shallower; such shallowerdepth is called Equivalent Air Depth (EAD).You can find the EAD’s for EAN32 ed EAN36 in the“AIR” column of the ESA “EANx Table 1” or calcu-late them with a simple mathematical operation:{ [F N2 x (Profondità + 10)] diviso 0,79} – 10.This formula can be used to calculate the EAD forany Nitrox mix; all you need to do is use the pro-per FN2 and the desired depth.For instance, 0,64 times 30 divided 0,79 and redu-ced by 10 = 14,3 metres, that is the EAD equiva-lent for 20 metres with EAN36. Diving at 20metres breathing Nitrox 39, is equivalent todiving at 14.3 metres with air; indeed the ppN2 at20 metres with Nitrox 36 is the same of that at14,3 metres with air.Note: all these operations (and the followingones) are considering that the ambient pressurein salt water increases by 1 BAR every 10 metres.

The modern computers behave the same more orless; you need to set the correct percentage of O2measured in the mix you are going to use, and thecomputers calculate the no decompression limitsbased upon the EAD.You will plan your dives many time during yourcourse, both with ESA “EAN 36 - EAN 32-Air DiveTables” and computer (if available).

You will have understood why Nitrox providesextended no decompression limits; anyhow, asusually happens, you have advantages and disad-vantages. In our case the latter is due to theincreased quantity of oxygen and is constitutedby a limitation in the maximum depth.As you have already learned during your ESAOpen Water Diver course, the oxygen is neededfor living but, when its partial pressure exceeds agiven amount, it becomes toxic; the maximumpartial pressure of O2 (PO2) that can be toleratedis set to 1,6 BAR.This is a very critical limit and, to guaranteesafety, you should not exceed 1,4 BAR PO2 whendiving. This gives you a safety margin in case you

Minitest1. The smaller nitrogenquantity in the Nitrox:a. It allows times of per-manence longer than withthe airb. It forces the scuba diverto long standstills ofdecompression c. It reduces the times ofpermanence within thelimits of not decompres-sion

2. The "EAD":a. It is to point out theEquivalent Air Depth(equivalent depth with theair) b. It serves for planningthe immersions with theNitroxc. a and b are exact

3. The effects of the gasesare due:a. To their partial pressure b. To the temperature ofthe underwater environ-mentc. To the partial pressureof another gas

Answers:1 a; 2 c; 3 a.

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should inadvertently dive deeper or longer thanyou should. Air, that contains 21% of oxygen, cannot causetroubles due to oxygen toxicity (hyperoxia) divingnot deeper than 56 metres if such limit is respec-ted. As the limit for recreational dives is set to 40metres, all breathing air divers that respect it arefar away from suffering any oxygen intoxication.Be careful! The maximum depth is not constantwhen breathing Nitrox; it changes with the quan-tity of oxygen, therefore you must carefully analy-se the mix contained in your cylinders.

Maximum Operative Depth (MOD)A workshop arranged to evaluate the conditionsof dives with Nitrox held in the 2000.Decompression physiologists, researchers, equip-ment manufacturers and technicians attended it.It was appraised that diving within the limit of 1,6BAR PO2 can be considered safe, provided that itis strictly respected and that exposition to oxygenis not excessive. Many computers consider safesetting the PO2 limit at 1,5 BAR.

To guarantee safety, you can decideto plan your dives in order to set thePO2 limit at 1,4 BAR, so that you canstill have a good safety margin incase you dive slightly deeper (itshould never happen even whendiving with air) provided you don’texceed 1,6 BAR.The ESA “EAN 36 - EAN 32-Air DiveTables” provides the MOD for thetwo common mixes: 36 metres forEAN 32 e 31 metres for EAN 36.These limits are based upon the PO2set at 1,5 BAR. You must plan anddive with Nitrox in order to neverexceed such depths. The operationthat enables you do calculate theMOD for a given mix is the following:[(1,5 x 10) : FO2] - 10 = MODComputers can work for you. Indeed, there arecomputers for dives with Nitrox that provideacoustic or visual alarm to the diver when rea-ching the PO2 limit set before diving. We will talkabout computer shortly.

EAN brea-thing 36 to31 metersthe samenitrogenquantity isabsorbedthat to 24meters withthe air

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PlanningPlan your dives as always done, making arrange-ments with a dive mate that is not less qualifiedthan you.Note: Instructors must be specifically trained todive with Nitrox too.Make sure the equipment is suitable for Nitroxand analyse the cylinder. The ESA Instructor willteach you how to do it; concentrate and try asmany times as possible; don’t hesitate to ask que-stions if you don’t feel confident.Analysing the cylinder is mandatory for each divewith Nitrox and is the first thing to do when pre-paring and planning your dives.The preceding paragraph explained that all youneed to do is concentrating on the percentage ofoxygen in the cylinder you will use. You will haveto analyse it personally, sign a specific registerand declare that you are aware of what you areabout to use and how to use it.You will find this procedure really simple afterhaving applied a few times, and you will feel moreconfident after having checked the content of thecylinder yourself. In many countries this procedu-re is dictated by the existing laws and local rules;get informed about them when you are planning atravel, as always. You can be properly assisted ifyou get in touch with an ESA Point or with ESANitrox Diver Instructor.After having checked the cylinder you can planyour dive, bearing in mind that a 1% tolerance isallowed; this means that a mix containing a quan-tity of oxygen that ranges between 31% and 33%can be considered to be EAN32.

TablesRespect all the rules you learned during your ESAOpen Water Diver course. Set the maximumdepth you want to reach and make sure it is com-patible with the limit set for the specific mix youwill use (EAN 36 = 31 metres – EAN 32 = 36metres).If the depth is compatible with such limit, you canlook for it in the ESA “EAN 36 - EAN 32-Air DiveTables” – Table 1, in the column related to themix you are about to use (EAN 36, EAN 32 or AIR);otherwise, you can use the next higher value.After you have identified the correct depth, moveto the right; you will find the EAD in the “AIR”column, then all times and the no decompression

Minitest1. The Nitrogen pp (PN2)to 30 meters, EAN brea-thing 36 is:a. 1,92 barb. 2,56 barc. 2,72 bar

2. The EAD for an immer-sion to 30 meters EAN 32breathing is:a. 22,4 meter b. 15,8 meterc. 24,4 meter

3.3. Considering the limitsof the course ESA NitroxDiver, the MOD for EAN 32are ______; while for EAN36 correspond to_______:a. 40 meter / 34 meter b. 36 meter / 31 meterc. 31 meter / 36 meter

Answers:1 b; 2 c; 3b.

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limit or, should it not higher, the Exposition toOxygen limit (120’).From this point you can proceed as if you wereplanning your dives with air.For instance, should you want to dive at 21metres using EAN32, while this depth is clearlydisplayed on the instruments you use during thedive, you will not find it on the table, therefore,you will have to consider the next higher availa-ble value. For the “EAN32” column, this value is22 metres, equivalent to 18 metres EAD in the“AIR” column.The no decompression limits (50’) is the same at24 metres with EAN36, at 22 metres with EAN32and at 18 metres with air. Basedupon the duration of the dive, thesame applies to the pressure group.The procedure for repetitive diveswith air applies also to repetitivedives with Nitrox. Once you decidethe maximum depth of the new dive,look for it in the “EANx Table 3”, inthe column related to the Nitrox mixyou intend to use. Intercept the linerelated to depth with the columnrelated to the pressure group andcomplete planning your dive as youalready know. For instance, assumeyou have dived at 20 metres for 39minutes using EAN32 during the firstdive, your pressure group is G. After1:30 hour-surface interval, the pres-sure group is E (see the EANx Table2) and you decide to dive at 15metres using EAN32. Identify the line of the “EANx Table3” related to the chosen depth andintersect if with the column relatedto the pressure group (E). you willfind the Residual Nitrogen Time of49’ (yellow cell) and the NoDecompression Limit of 81’ (greencell).You should not dive more than three times usingNitrox during the same day; indeed, should youchoose to dive three times, it is advisable to diveusing air within 18 metres the third time.You can plan to have repetitive dives using diffe-rent Nitrox mixes and air. Be careful when usingthe dive planner, specifically when looking for the

Before use remembersto alwaysanalyze theair mixture

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depth and the column related to Nitrox or pressu-re group: should you make any mistakes you maybe subject to Decompression Disease or hypero-xia. For the same reason, remember to set thecorrect oxygen percentage before diving with thecomputer.Let’s consider the following example: Andrew andMichael are going to dive at 27 metres usingEAN32. what is the maximum operative depth forthis Nitrox mix considering a limit PO2 of 1,5BAR? 36 metres, therefore they made the rightchoice. To plan the dive, they look for the depthin the “EAN32” column of the “EANx Table 1”; as27 metres is not included in the table, they mustconsider 29 metres. They read the Equivalent AirDepth in the “AIR” column (24 metres) then theno decompression limit (30’), choose the durationof the dive and identify the related pressuregroup. The two friend decide to dive at 27 metresfor 25 minutes; the pressure group at then of thefive is F.They plan a repetitive dive on a rocky seabedclose to Butterfly Head; they have to sail forabout 2 hours and 30 minutes, a good surfacetime that makes the F pressure group turn to C.The maximum depth for the second dive is 20metres, and they will use EAN36. After havingchecked with the analyser that the oxygen per-centage stated on the card attached on the cylin-der is correct, they use the “EANx Table 3”. Theylook for the chosen depth in the EAN35 columnand intersect the related line with the columnspecific to the C pressure group. The ResidualNitrogen Time is 21’ (yellow cell) and the new NoDecompression Limit is 49’ (green column).The place is really nice, but they dive for 45 minu-tes only. Adding the actual duration of the divewith the Residual Nitrogen Time they can use thepressure group at the end of the second dive (45+ 21 = 66 minutes, corresponding to the I pressu-re group).As you see, things change if you compare diveswith air to dives with Nitrox. You must take careof the oxygen percentage, identify the relatedmaximum operative depth and make sure younever dive deeper.You must make sure you will never exceed theallowed exposition to oxygen, although this isalmost automatically respected if you respect allparameters related to recreational dives. Avoid

The EANxTable 3 pointout the nitro-gen residueand the newlimit of notdecompres-sion for theconsecutiveimmersions

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diving more than three times, or to dive for morethan 120 minutes for a single dive or 180 minutesfor repetitive dives over 24 hours.Some computers calculate the exposition to oxy-gen based on the percentage of the maximumtolerable quantity: make sure you don’t exceed90% over 24 hours; indeed, make sure you main-tain well under this limit. You will see that divingcautiously you will enjoy your dives more.

With the computerShould you wish to dive with a computer, makesure it can calculate dives with Nitrox. Checkcarefully the oxygen percentage set; for instance,the display must show that the it is set to 36% incase you dive with EAN36. Remember, there areseveral models of computers able to plan diveswith gas mixes other than air; read the usermanual carefully to be sure you use your compu-ter correctly and safely.Dive applying the techniques you learned duringyour ESA OWD course and as stated in the ESAAdvanced Diver manual and ESA Computer Divermanual.Remember that you must respectthe maximum depth related to thePO2 and that you always must verifythe percentage of oxygen set, spe-cially when changing mixes from onedive to the other.Try to imagine the consequences ofdiving with first time with EAN36,setting the oxygen percentage at36% and the second time with airwithout changing the computer set-tings. You would believe that youhave not exceeded the no decom-pression limits while you havealready exceeded them; you wouldascend unsafely and be subject tothe decompression disease.As you have read in the previousparagraph, the computer providesthe exposure to oxygen percentage showing num-bers or graphically. Should you exceed the 50% ofthe tolerable exposure, wait at least for an hourbefore diving again (this should be done anyway),make sure you don’t exceed 90% over 24 hours(or any other value indicated the computer manu-facturer). Whenever you should exceed such

Always veri-fies perso-nally , withthe O2analyser,that the per-centage ofO2 pointedout on thelabel is exact

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limit, don’t dive for 12 hours at least.At this stage you may be asking yourself if you candive with Nitrox when the oxygen percentage isset to 21% (air) in the computer. Yes, you can doit. indeed, the no decompression limits with aremore stringent than those for Nitrox, so youwould be safer. Some divers use this procedure toincrease the safety margins in case of repetitivedives. Anyhow, you must remember to analysethe gas mix you are about use for your dive andnot to exceed the maximum operative depth rela-ted to the oxygen percentage, in order not to besubject to PO2 beyond 1,5 BAR (the computers forair don’t provide any alarm in case you exceed it,so you must respect it).Should the computer fail while diving, react inaccordance with the procedure you learnedduring the ESA OWD course: ascend without wai-ting any longer but slowly to 5 metres and have along safety stop, as far as the left quantity ofNitrox you have enables you to do it.The usage of computers for dives with Nitrox isquite similar to that for air and the rules to berespected are the same. Once again, read care-fully the user manual supplied by the manufactu-rer. Should you wish to improve your knowledgeon computers, you can attend the ESA ComputerDiver course.Be cautious! As you know, thanks to its capabilityto calculate the nitrogen absorption, the compu-ter let you dive longer if you dive starting deeperand then ascend to shallower depths in order toreduce the nitrogen absorption rate. You will beable to dive even longer using Nitrox, so plan yourdives in order to start to ascend well in advanceof getting close to the no decompression limit,respect the maximum operative depth and takeinto account the exposition to oxygen.

British systemSome countries use the British system. For instan-ce, if you dive in the Caribbean Sea and hire yourequipment, you will use instruments that measu-re depth in feet. Therefore, you will have to con-vert measures. Remember that 10 metres corre-spond to 10 feet and that 1 BAR is 14,7 PSI. Theappendix to this manual will provide conversiontables and formulas to calculate maximum opera-tive depth, equivalent air depth and partial pres-sures. If you bring your computer with you, you

A computerfor theimmersionsNitrox thatvisualizes thenitrogenabsorptionand theexposure tothe oxygen

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will not need to make any conversions.

DivingDiving with Nitrox is just like diving with air; youonly need to take care of all the parameters anddon’t exceed the maximum planned depth.Oxygen intoxication can affect the CentralNervous System and have no premonitorysymptoms ; therefore respecting the maximumoperative depth is mandatory.For instance, should the limit be 31 metres, pre-pare yourself mentally and physically in order notto exceed 29/30 metres; this gives you a goodsafety margin in case of distractions. If you aresupervised by a Diveleader, dive shallower thanhim and plan your dives in sites where exceedingthe maximum operative depth is not that easy.To avoid problems due to oxygen intoxication,remember to respect the limits established forthe global exposition to oxygen over 24 hours.Your ESA Instructor and the dives included in thecourse will teach you to control these two impor-tant parameters and avoid problems. By the way,the depth limits are established also for diveswith air, therefore, we can barely state that divingwith Nitrox doesn’t introduce anything new:either way, a good diver must be able to controlall the instruments to monitor all parameters andrespect all limits. You do the same when youdrive your car: you monitor the speed to avoid toexceed the limits and check any warning lights.This helps in avoiding fines, running out of petrolor damaging the engine.So, checking your instruments while diving, andmaking sure your dive mate does it as well, youavoid exceeding the depth limits in order to pre-vent nitrogen narcosis or oxygen intoxication, andmake sure you don’t exceed the no decompres-sion limits, reducing the chances to get decom-pression sickness; you avoid running out of air orNitrox in order to prevent sudden and uncontrol-led ascends. Being perfectly trimmed helps inexceeding the limits, so that you can be morerelaxed while diving, and concentrate on whatyou are doing.Considering how dangerous the effects of oxygencan be, should you feel and symptoms imputableto this gas, ascend and get out of water withoutwasting time, and don’t dive for 24 for hours as aminimum.

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Minitest1. In the immersions withNitrox, the analysis of theoxygen from who uses it isa considere procedure:a. obligatoryb. useless c. optional

2. To plan an Nitrox divewith the ESA table is neces-sary to know:a. the EAD b. the MODc. a and b are exact

3. Using the underwatercomputer, when we chan-ges type of mixture it isimportant:a. to vary the percentage ofO2 on the tool b. to wait for 24 hours bet-ween an immersion and theotherc. a and b are exact

Answers:1 a; 2 c; 3 a.

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Analysing oxygenAs you have read, you must analyse Nitrox cylin-ders to check the oxygen percentage before usingthem. This procedure is one of the few things thatchange from diving with air. It may look a bit com-plicated at the beginning, but you will find iteasier and easier as you get experienced; themost important things is that the oxygen analysermust be correctly set. This component was origi-nally developed for health purposes, and is widelyused in hospitals to monitor the percentage ofoxygen supplied to patients. Specific oxygenanalysers have been developed since when diffe-rent gas mixes are used for diving. Usually, theanalyser consists of a sensor, a transducer, acoaxial cable, a computer with liquid crystal dis-play, buttons to switch it on and set its functionsand parameters. Some analysers can providemaximum operative depth and equivalent airdepth for the analysed Nitrox.The same rule applicable to computers apply toanalysers: you must read the instruction in theuser manual and respect them. Your ESA NitroxDiver Instructor will teach you (maybe he hasalready done it) to use one or more analysermodels. Pay attention to his lessons and don’thesitate to ask questions; try the procedure untilyou feel you have learned perfectly. Should youbuy or use an analyser different from what youhave used during your training, ask information tothe dealer or the operator that is supplying it.Anyway, some procedures are always the same,no matter the analyser model:

- make sure you deal with professional and relia-ble diving centres

- read the user manual

- check that it is fit and that the batteries arecharged (or perfectly connected to the electricline)

- verify that the sensor is properly working andnot expired (read the terms related to its substi-tution provided by the manufactured)

- connect the cable to the computer and to thesensor correctly

Minitest1. In the Nitrox dives:a. it needs to foresee toascend with at least 100bar in the cylinderb. it behaves us as in theother immersions, monito-ring with attention depth,time and manometer c. variations of depth can-not be effected

2. To respect the time anddepth limits is important for:a. to prevent the MDD and theoxygen poisoning b. to avoid excessive loss ofheatc. to prevent the MDD

3. If imputable symptomsto oxygen poisoning aremanifested:a. ascent for 1 meter andcontinue the dive b. immediately ascent, onsurface, to go out of thewater and not to effectdives for at least 24 hoursc. stop on the bottom andto restore the control ofthe respiraton

Answers:1 a; 2 c; 3 b.

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- its operability can be compromise by extremetemperatures, altitude and pressure variations,humidity and condensate (see the instructions)

- avoid holding the sensor and your hand palm

- turn on the analyser and check thedisplay and wait that the numbers itshows stabilise to fixed values

- set the instruments using air (21%O2) and, possible, with pure oxygen(…99% O2)

- use a flow meter to make sure thatthe sensor is receiving the correctflow of gas; this is of fundamentalimportance to prevent dangerousconsequences due to wrong readingsby the analyser

- make the analyses 3 times andmake sure you always get the samevalues

- if appropriate, make the check withair (21% O2)

- should the instrument provideadditional functions (maximum ope-rative depth, pp O2, no decompres-sion limits, equivalent air depth...)make sure you have correctly setthe right data and respect theinstructions provided by the manu-facturer

- turn off the analyser and store itadequately (unless anybody elseneeds to use it)

- write the oxygen percentage on thecard and on the register

- write the MOD for the analysed depth on thecard

- sign to confirm you have analysed the cylinderand that you know the O2 percentage in the cylin-der you will use

Example of O2analyser

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When the flow meter is not available, some diversuse to measure the oxygen percentage puttingthe sensor in a space saturated of the Nitrox mixto analyse.You can use a plastic bag with a hole for the sen-sor and another for the regulator; in this case, asthe sensor doesn’t work well when the pressureincreases, you must avoid to inflate the bag too

much. Furthermore, it is importantto “wash” the bag, filling it up withNitrox and then emptying it 3 timesbefore proceeding with the analysis.Anyhow, a flowmeter is preferable.Should you not use the instrumentfor long, remove the batteries anddisconnect the sensor before puttingit away; the sensor must be stored inits specific container. You must puteverything in a place with no humi-dity, away from sunlight and extre-me temperature.Respect all instructions related tothe sensor substitution. You mustknow that the life of the sensordepends on its exposition to oxygen,irrespective from the fact that it isconnected to the analyser.You will have understood that theoxygen analysis is the most impor-tant part of the preparation for thedives with Nitrox, therefore, youmust get skilled in analysing yourcylinder. Anyhow, as already stated,it is not a complex operation; fur-thermore, remember that the newanalysers provide reliable results if

the instructions provided by the manufacturersare respected.

Is funda-mental toread withattention theinstructionsof the pro-ducer of theO2 analyser

Watch OUT! The sensor contains a liquid that can be harmful, it avoids to touch it if you notice los-ses of liquid, both that you deal with a sensor in use or that you deal with a new sen-sor, in this case it is advisable to avoid to open the wrapping that contains it (usuallytransparent). If the sensor introduces signs of usury and loss of liquid it must be replaced, in anycase it is had to try to mend its hull with glue or other.In case of accidental contact with the liquid it is necessary to wash abundantly thestricken area with current sweet water and to look for medical intervention.

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Now you can plan, together with your ESA NitroxDiver Instructor, your first dives with Nitrox. You willbe exited and curious of trying it. You have alreadyestablished the basis to become a skilled ESA NitroxDiver: you know what Nitrox is, you know the basicterminology, you know why it extends the nodecompression limits. You can calculate the partialpressure of the gasses at the various depths, themaximum operative depth and the equivalent airdepth for the two main Nitrox mixes. You have usedthe mathematical formulas to plan your dives and tobetter understand how to use Nitrox, and know thefundamental steps for analysing it.Analyse the cylinder you will use together with yourInstructor, plan your dive and enjoy your first expe-rience with Nitrox. Next chapter will provide detailedinformation on other important features of divingwith Nitrox.

1Minitest

1. Among the O2 analyser'scomponents there are:a. sensor, cable, tool andsystem of settingb. sensor, cable, wrist strapand system of setting c. system of setting, cable,microphone and tool

2. The analyser's sensor for O2:a. it must be replaced respec-ting the indications of themanufacturing house b. it is sensitive to the dampand the variations of pressurec. a and b are exact

3. Analyzing the air, the analy-ser for O2 has to notice:to. around 79% of O2b. around 21% of O2c. around 32% of O2

Answers:1 a; 2 c; 3 b.

Congratulations!

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What have You learned?This exercise will let your review all the most importantinformation contained in this unit, so that you canimprove your preparation and be ready for your nextappointment with your instructor. Answer the questionschoosing the right questions among the listed ones.Check you answers with your Instructors; in case of anyinaccuracy, he will provide all the needed explanations.

1. The Nitrox is a gas mix composed of:a. oxygen and nitrogenb. helium and oxygenc. helium, nitrogen and oxygen

2. The two most diffused Nitrox mixes are:a. EAN 37 e EAN 25b. NOAA Nitrox IV and NOAA Nitrox Vc. NOAA Nitrox I and NOAA Nitrox II

3. The reduced quantity of nitrogen:a. extend the no decompression limitsb. reduces the effects of nitrogen narcosis c. both a. and b. are correct

4. The nitrogen partial pressure in the Nitrox 36 mix atthe sea level is:a. 1 barb. 0,36 barc. 0,64 bar

5. The EAD for a dive at 19 m with EAN 32 is:a. 14,97 mb. 24,97 mc. 13,49 m

6. The no decompression limit for a dive at 27 metreswith EAN 36, in the ESA Tables is:a. 25 minutesb. 40 minutesc. 30 minutes

7. The no decompression limit for a dive at 27 metreswith air, in the ESA Tables is:a. 25 minutesb. 40 minutesc. 30 minutes

8. The maximum PO2 limit to take into account whenplanning dives with Nitrox is:

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a. 1,8 barb. 1,5 barc. 0,5 bar

9. The divers that use a computer, before diving withNitrox must:a. read the instructions provided by the manufacturerb. set the O2 percentage correctlyc. both a. and b. are correct

10. MOD means:a. minimum operative depthb. maximum operative depthc. the ascend procedure after dives with Nitrox

11. The depth limit using EAN 30 is:a. 30 metresb. 40 metresc. 38 metres

12. The analysis of oxygen:a. can be done only by the operators what rechargethe cylindersb. can be done by the Nitrox Instructorc. must be done by the end-user

13. In case of signs of oxygen intoxication::a. ascend a bit and continue the dive b. emerge and get out of the waterc. emerge, get out our of the water and don’t dive for24 hours

14. For a more accurate oxygen analysis:a. you should use a flow regulator b. you should keep the sensor on you hand palmc. you should set the instrument in order to read 79%on the display

15. To avoid damages during the oxygen analysis, thesensor must be substituted:a. every 4 yearsb. in accordance with the indications of the manufacturerc. every 6 years

I declare that I have reviewed all the wrong answerswith the ESA Instructor, and that I have understood therelated explanation.

Signature __________________________date_________

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Chapter TwoWhat will you learn?

The preceding chapter provided the informationyou need to plan your dives with Nitrox; maybeyou have already used such information for yourfirst dive with such a mix. As anticipated, thereother important information that can help you inmaking you more aware about diving with Nitrox;this will help you improving your safety and conti-nuing your diving career.

This chapter will answer questions such as: ismore convenient using air or Nitrox? Which arethe advantages of Nitrox? Which are the relatedcomplications and disadvantages? Do I need tochange my equipment to use Nitrox? How areNitrox cylinders identified? How are the EANxmixes prepared? Who can recharge Nitrox cylin-ders? Who must analyse the oxygen percentage?What are the effects of carbon dioxide? DoesNitrox eliminate Decompression Sickness andNarcosis? What should I do if I see an accident?How can I bring help?All the subjects answering the above questionswill be treated in accordance with the recreatio-nal dives philosophy, simplifying the most difficultconcepts without forgetting the information thatimprove your safety and the advantages of diveswith Nitrox.

MiscellaneousIf you add oxygen to air, the percentages of oxy-gen and nitrogen change: the first increases andthe second decreases. The same happens if youremove nitrogen from air. Let’s have a look atadvantages and disadvantages of Nitrox. As youalready know, the main advantage is the exten-sion of the no decompression limits; this featureis more appreciated when diving between 15 and30 metres. Thanks to Nitrox you will be able toexplore a site for longer without exceeding the nodecompression limits.You may think that diving with hyper-oxygenatedmixes, respecting the no decompression limits forair, causes safety improvements. This is partiallytrue if you consider that comparing to dives atthe same depth for the same time, one with

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Nitrox and one with air, the nitrogen absorption isreduced with diving with Nitrox.Anyhow, under a mere statistic point of view, thedegree of occurrence of decompression sicknessis really small also fordives with air, therefore,Nitrox cannot be conside-red 100% safer than air. Nitrox reduces the affectsof nitrogen narcosis;nevertheless, high pressu-re oxygen can cause simi-lar effects. Therefore,admitting that Nitrox eli-minates completely theeffects of narcosis is notcorrect.Many divers state thatafter dives with Nitroxthey are less weary thanthey are after dives withair, and that under waterthey are much more con-centrated; indeed, it isoften used on cruisesboats and by guides whodive many times everyday. Planning dives with Nitroxis not so different fromdoing it with air. You haveto take into considera-tions some specific fac-tors: availability of Nitrox,need to check the oxygenpercentage, limits (depthand time) related to oxy-gen toxicity to the centralnervous system (CNS) andfor the whole organism(mainly to lunges).Although Nitrox is sti llhardly available in somecases, it is getting moreand more diffused. Shouldyou participate to divingcruises with people that dive exclusively withNitrox on a boat equipped to produce it, why notusing it? Thanks to new technologies and impro-ved systems to produce oxygen enriched air,Nitrox recharge stations are more and more diffu-sed in many diving centres of the most famous

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locations for dives.The analysis of the oxygen percentage may seemto request extra efforts but, as stated severaltimes, a bit of experience makes it become a verysimple procedure that doesn’t take too long; fur-thermore, you will feel safer and will enjoy your

dive more if you analyse your ownNitrox cylinder..Should you have doubts on the dataprovided by the oxygen analyser, ifthe diving centre is serious and relia-ble, you can decide to plan your divein order to limit the depth to thehighest oxygen percentage measu-red and the no decompression limitto the lowest value. You will be sureto avoid both decompression sick-ness and oxygen intoxication to yourCNS. Oxygen toxicity for the CNS isextremely serious as it can affect thedivers’ health; anyhow, to preventany related problems, respect thePO2 limit of 1.5 bar and the maxi-mum exposition to oxygen that iscommonly agreed by many scientists(doctors, physiologists and resear-chers). As you know, there are limitsto be respected also when you divewith air; while the disadvantage ofdiving with Nitrox is that such limitsare more stringent, they are justifiedby the longer dive time and that,anyway, maintains the exposition tooxygen within safe and acceptablelevels.Planning dives bearing in mind themorphology of the seabed is advisa-ble: this avoids exceeding the maxi-mum depth and helps in taking themost from Nitrox. The recreationaldiver that, thanks to the ESA DeepDiver course, can dive down to 40metres, cannot reach this depth nei-

ther with EAN36 nor with EAN32.Oxygen toxicity to the human organism (mainlyfor lunges) can be controlled respecting the expo-sition time indicated in the NOAA tables, i.e. 120minutes for a single dive and 180 for the repetiti-ve ones.Finding a balance is the only way to enjoy the

The Nitroxhelps to reducethe effects narcotics of thenitrogen

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advantages of Nitrox; to do this, take in dueaccount the type of dive and the objective toreach. Probably, diving on a wall, with the compu-ter, following a multilevel path, you don’t need touse Nitrox as this kind of dives let you stay underwater considerably long. You know that, shouldyou want to explore an area between 23 and 27metres to look for a specific organism or to enjoythe spectacular gorgonias, the no decompressionlimit is 25 minutes with air and 40 minutes withEAN 36 (equivalent air depth 21 metres); you maydive at the maximum depth for about 26/37 minu-tes maintaining a good safety margin and beingmore concentrated.Considering that when you breath Nitrox thenitrogen absorption is reduced, you can decide touse it even if a specific dive don’t let you enjoythe advantages of extending the no decompres-sion limits.As already said, you will have to take into accountNitrox availability, but there is another factor tobe considered: cold. Sometimes enjoying theadvantages of Nitrox is difficult because of coldwater limiting the dive duration.Another issue could be the air (orNitrox) consumption. These issuescan be solved using bigger cylindersand diving either in warm seas orwith a dry suit.

Calculating your air/Nitrox con-sumptionConsider that a person breath about20 litres of air per minute in regularconditions at sea level; as you lear-ned during the ESA OWD course, theconsumption must be related to thespecific depth you are diving. Thus,at 30 metres (4 ATA) the consump-tion is 80 litres per minute (20 litresx 4 ATA).As you know, a 15-litre cylinder char-ged at 200 bas contains 3000 litresof gas (air or Nitrox, 15 litres x 200 bars). Thecylinder duration ad 30 metres can be estimateddiving 3000 by 80 (3000 litres/80 litres per minu-te = 37.5 minutes). The gas consumption changesfrom diver to diver and depends about specificconditions: breathlessness and cold, as well asfatigue, can drastically increase the gas consump-

The safetystop for 3minutes to5m must also be effec-ted in theNitrox dives

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tion. Therefore, this calculation, can only helpyou in understanding if the capacity of a specificcylinder can support the no decompression limitsextended by diving with Nitrox. Although this cal-culation is based on conservative assumptions,you must check your manometer frequently, andremember to emerge when the cylinder pressureis 50 bars.

Heat dispersionTo prevent excessiveheat dispersions andenjoy the potentialityof Nitrox you shoulddive where the tempe-rature of the water ishigher than 22°C,during the warm sea-son, when it is hot, orusing a dry suit.The dry suit reducesthe heat exchange witwater thanks to the airbetween the suit andthe skin of the diver.Remember that to usea dry suit safely youshould be trained! Ask

your instructor about the ESA Dry Diver Course.Using a dry suit is not difficult, but it takes theright training and experience; on the other end, itgives you the possibility to extend the dive timein cold water. The newest diving equipment is both more andmore reliable and comfortable; it gives divers thepossibility to enjoy diving thoroughly. The nextparagraph deals with equipment and how theyrelate to oxygen enriched mixes. The outcome ofthe analysis per next paragraph is that usingNitrox is always the best choice: it extends the nodecompression limits, the chance to suffer ofdecompression sickness is reduced thanks to thefact that you breath less nitrogen, you can bemore concentrated and, last but not least, youwill be less tired also after some repetitive dives.

EquipmentThe oxygen oxidizing features, as well as the com-bustion supporting power, depends on its concen-tration.

Controlsystem ofoxigen filling

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Warnings and procedures related to equipment todive with Nitrox are based on such features.In addition to taking into account all the precau-tions with equipment and related maintenanceyou learned during your previous courses, youneed to consider that some materials (such asrubber) get worn faster if exposed to high oxygenconcentration. This may cause some malfunc-tions.Furthermore, remember that grease (hydrocar-bon for instance) mixed with oxygen causes com-bustions, as well as flames or sparks due to elec-trical discharges.Sudden combustions can cause explosions whichput in danger people, animals and things.The outcome of the workshop about Nitrox divingheld in 2000 referred to in the first chapter, isthat the standard equipment can be used with gasmixes containing up to 40% of oxygen, unlessotherwise specified by the manufacturer.Luckily, the recreational divers use enriched airmix with a 40% maximum percenta-ge of oxygen; furthermore, themost two common Nitrox mixes,EAN32 and EAN36, contribute tomaking the equipment exposed tolower percentages.Very good news! You don’t need tochange your equipment to start thisnew exiting adventure.Be careful although! The abovedoesn’t apply to cylinders and val-ves, which need to be specificallyapproved for oxygen enrichedmixes: we will treat this topic in awhile.Although you can dive with theequipment you usually use for diveswith air, you should think aboutusing oxygen compatible compo-nents.Every time you have to overhaul your equipment,inform the technicians that you are using Nitroxand ask them to add the improvements needed(specifically, they will take care of seals, rubbercomponents and lubricants).Should you have to buy a new piece of equip-ment, consider the possibility to buy componentsdesigned to withstand Nitrox; for instance, asbuying a good regulator improves safety, you

A Nitrox-dedicatdregulator

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should buy one that is designed to be used at oxy-gen high concentrations. This will make yourdives safer and you will enjoy the more.All the other recommendations you receivedduring your ESA Open Water Diver course andsubsequent ones apply to dives with Nitrox aswell; of course, your equipment must includeBCD, manometer, emergency regulator andinstruments needed to measure depth and time.

CylindersAs you know, the cylinders must comply withrules and regulations of a specific the country. You will remember that you can find the datastamped close to the neck of the cylinder; thisdata is related to the gas that can be contained inthe cylinder, its capacity, the nominal pressureand the hydrostatic one, as well as the date thenext hydrostatic test will have to be performed.

Cylinders for Nitrox have the samedata; the difference is that insteadof specifying “air” as the usablegas, the stamped data shows “EAN”.Sometimes you could find “air ”cylinders charged with Nitrox. Inthis case, the oxygen percentagewill be less than 40% and a specificadhesive label must be attached tothe cylinder.

A recent European rule establishedthat the dome of the cylinder mustbe painted with colours specific tothe gas contained. So air cylindershave black and white segments,oxygen cylinders are all white,Nitrox cylinders are blue, heliumones are brown. Other regulationsand procedures establish that

Nitrox cylinders must be clearly marked with ahorizontal yellow band with “Nitrox” or “EnrichedAir” or “EANx” printed in green (the two colourscan be exchanged between them). Each cylinder must be equipped with card or stic-ker with the following information: type of thegas mix contained and when it was recharged,results of the O2 analysis performed by the blen-der and the name of the blender itself, the MOD(maximum operative depth) based upon the maxi-

It’s funda-mental tomake thecylindersNitrox reco-gnizable

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mum PO2 and the oxygen percentage measure bythe end user.In some cases you can find Nitrox cylinders whatlooks like those used for air; in this case, makesure that at least the card or sticker with theabove data attached to it; remember: avoid dea-ling with operators who don’t respect those pro-cedures useful for prevention. Remember, thatNitrox cylinders must clearly state the type of gascontained and the type of gas they were manu-factured for; this is important for the two follo-wing main reasons: 1) risk of explosion due to thehigh oxygen concentration 2) risk of suffering ofdecompression sickness or because of high oxy-gen concentration.Flames and sparks, as well as traces of hydrocar-bons in the cylinder and lubricants used, cancause explosions because of the high oxygen con-centration.Air recharge stations can push small quantity ofhydrocarbons inside the cylinders. Furthermorethe valves for air cylinders don’t use materialssuitable for oxygen (specifically seals and lubri-cants)Usually, reliable and professional recharge sta-tions respect all the safety procedure. Therefore,you don’t need to worry too much; concentrateon choosing the services offered by qualified andprofessional personnel instead. One point mustbe duly taken into account and respected byNitrox divers: the cylinders for compresses gassesmust be used for the type of gas they were pre-pared for, tested and certified. Recharging a cylin-der with a different gas is dangerous as it cancause explosions; therefore, don’t charge a Nitroxcylinder with any other gas, and vice versa.

RechargingAlthough an enormous number of people drivetheir car everyday, very few of them know theprocedures used by a refinery to produce the fuelthey use. In the same way, Nitrox divers don’tneed to know the procedures used to obtainNitrox perfectly. Therefore, we will not providetoo many details, but some basic information isuseful to better understand Nitrox. Furthermore,should you choose to become a professionaldiver, these notions will constitute some of thefundaments of your knowledge.As you may have already understood reading the

Minitest1. The principal advantagegiven by the use of theNitrox is:a. the facility with whichcan be retrievedb. the increase of thetimes of immersion withinthe limits of not decom-pression c. a greater duration inthe time of the equipment

2. Another very importantadvantage is:a. the best lucidity of thescuba diver during theimmersion b. the total disappearanceof the problems of narcosisc. a and b are exact

3. Considering a consump-tion of 20 liters to theminute in surface, howmuch does a cylinder of 10liters last (x 200 bar) to thedepth of 10 meters?:a. around 100 minutes b. around 50 minutesc. around 35 minutes

Answers:1 b; 2 a; 3 b.

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preceding paragraphs, there are to main procedu-res for obtaining Nitrox: 1) adding oxygen to theair 2) removing nitrogen from the air.Let’s review them together bearing in mind thatthey can only be performed by specifically trainedand qualified blenders.

Partial pressure rechargeThis procedure is quite dangerous because isbased upon pure oxygen being pumped in a cylin-der already containing air or that will be addedafter the oxygen. It seems easy to use but must becarried out by highly professional blenders withoil free equipment to avoid explosions. Specifictables tell the blenders the quantity of oxygen tobe added to air or other known mixes with oxygento obtain the chosen typo of Nitrox. Getting thedesired mix with a good accuracy is quite difficult

with this procedure.

Continuous flow mixA specific equipment add oxygen, ina controlled way, to the air thatbefore it flows through the com-pressor; this way the blender cananalyse the mix and change the oxy-gen flow rate until the oxygen per-centage is the needed one. Thisprocedure avoids the pure oxygenfrom flowing through compressor,valves and cylinders, reducing con-siderably the changes to haveexplosions.Anyhow, using oxygen compatibleequipment are strongly recommen-ded and usually requested by law.

Nitrogen removal from airThis procedure was conceived considering themethod used by the agriculture industry to pro-duce nitrogen (needed for fertilizers), thanks tofilters capable of letting the nitrogen flow andblocking the oxygen. Changing the setting ofthese filters it is possible to remove form the airthe proper quantity of nitrogen and obtain thechosen Nitrox. This procedure avoids contactsbetween pure oxygen and the equipment used.Anyhow, considering the high concentration ofoxygen and the high pressure, using oil free mate-rials and lubricants is preferable. Furthermore,

Cylinder ofoxygenused in therechargeNitrox forpartialpressures

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this procedure eliminates the needs of storingpure oxygen. The disadvantage is that producingdifferent types of Nitrox is difficult; this system ismore productive when preparing one specifictype of Nitrox.

These are the main procedures used to produceNitrox. Remember that to apply them you mustbecome a trained and qualified blender. The ESANitrox Diver course doesn’t enable you to do it;this is done by specific qualifying agencies.Furthermore, the recreational divers finds theperfect equilibrium between safety and recrea-tion respecting the rules and procuring Nitroxfrom professional diving centres able to producethe most diffused and standard mixes (EAN 32and EAN 36).One very important feature of the oxygen usedfor Nitrox is that it is medical oxygen; it purer andis specifically produced to be breathed. Oxygenfor welding is forbidden.Usually, the diving centres that recharge Nitroxask the divers to show the Nitrox Diver licence, toanalyse the mix and to sign a register; it seemsthere are too many procedures to respect, butthey are all aimed at your safety and demonstra-te the people you are dealing with are professio-nals. Therefore, try to be collaborative and don’ttrust those who underestimate these procedures.To avoid chances of contamination, the Nitroxrecharge stations (as well as those for air) shouldbe equipped with special filters and be regularlymaintained with extreme care and seriousness.These are some of the features to be taken intoaccount when evaluating professionalism andquality of a recharge station:• request to show the licence• order and cleanness of the recharge area• type of oxygen used• well identified cylinders• usage of the card or sticker with the informa-tion about the cylinder• filling in and signing the register• request to analyse the O2Ask for information about the recharge stationsof your town to your ESA Instructor or to an ESAPoint (www.esaweb.net).

OxygenEverybody knows how oxygen is important for

Minitest1. The use of oxygen in highconcentrations (over 40%):a. it asks for particularattentions for it’s ele-vated inflammabilityb. it doesn't foreseesome type of precaution c. improve the dura-tion of the equipment

2.With EAN 32 andEAN 36, the scuba divercan use:a. only Nitrox-devotedequipment b. also the normal equip-ment for the air, if otherwi-se specified not from themanufacturing housec. only equipment compa-tible oxygen

3. The cylinders for the aircan contain Nitrox:a. provided that the oxygenthat comes into contactwith the tank doesn't over-come 40% b. only if the recharge hap-pens with particularsystems and the cylindersare identifiable however c. a and b are exact

Answers:1 a; 2 b; 3 c.

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livings. Not everybody knows it can become dan-gerous. You have already learned during the ESAOpen Water Diver course that too low (hypoxia)and too high (hyperoxia) oxygen partial pressurescan cause serious conditions that can put life indanger.The oxygen partial pressure can become too lowduring a long free dive or while ascending from afree dive after a too long hyperventi lation,making the diver faint.These are all problems treated during the pre-vious courses; hypoxia can also be caused by atoo low quantity of oxygen in the gas mix and canbe prevented analysing it before diving.

Considering the high oxygen partialpressure in Nitrox mixes, we take acloser look at the problems causedby hyperoxia, specifically oxygenintoxication to whole body andlungs, and intoxication to the centralnervous system (CNS).

Intoxication to whole body and lungsRecreational divers can hardly sufferof this problem. Indeed, it is a pro-blem that may affect those diverssubject to long exposure to oxygenpartial pressure greater than 0,5BAR. Usually, depth and no decom-pression limits, as well as those rela-ted to air consumption and cold(heat exchange with water) avoidthe recreational divers from beingexposed to oxygen long enough tofeel the symptoms. Such kind of pro-blems, instead, can be suffered bythose divers who work under waterconsiderably long, even in shallowwater. These problems must betaken into account by technicaldivers as well: the usage of high oxy-gen concentration mixes duringdecompression stops reduces signifi-

cantly the duration but increases the expositionto oxygen which must be carefully monitored.Medical oxygen used for therapeutic purposescan cause intoxication as well.There are two measures for exposure to oxygen:the Oxygen Toxicity Unit (OTU) and the UnitPulmonary Toxicity Dose (UPTD). Specific tables

Through thetransparentplastic hosea flow arri-ves assem-bled of O2that is mixedwith the airinhaled bythe presser

37

let you calculate these measures for given PO2and dive duration; they are then used to calcula-te the exposure percentage which must not gobeyond the limits established in special tables toavoid risks.According to the outcomes of the workshop onNitrox cited at Chapter 1, the divers that respectthe limits recreational dives don’t need to measu-re the exposure for the whole body. They need totake into consideration the central nervoussystems (CNS) exposure to oxygen instead.

Oxygen intoxication to the central nervoussystems (CNS)Oxygen intoxication to the CNS is caused by highoxygen partial pressure and/or a long exposure.Long exposures can be dangerous starting from aPO2 of 1,3 BAR. Therefore, respecting the limitsestablished by the NOAA is really important: PO21.5 BAR, duration of a single dive 120 minutes,overall duration of repetitive dives 180 minutesevery rolling 24 hours, 3 maximum dives withNitrox in one day.Susceptibility to oxygen intoxicationchanges from diver to diver and fromtime to time. One important point isthat the symptoms may reduce whilediver is ascending, but they can startwithout any premonitory and propersigns; therefore, the diver is takenby surprise and, should he be victimof convulsions, he risks to drown.Many serious accidents happeneddiving really deep with air were ori-ginated by oxygen intoxication to theCNS: this is another good reason torespect the limits!

“CNS Oxygen Clock”This is a procedure used to monitorthe CNS exposure to oxygen; it wasestablished by the NOAA.The CNS exposure to oxygen candetermined thanks to the limits established in theNOAA table “oxygen exposure limits per dive”either using the maximum PO2 or analyticallyusing other tables that provides a percentage ofexposure as a function of the time spent for eachPO2 during the dive (CNS%).Safety is improved thanks to the indication provi-

2Particular filters canimprovenotably the purity ofthe airduring therecharge

38

ded by the NOAA for the maximum PO2; theanalytical procedures are more useful for techni-cal divers that breathe different oxygen concen-trations for pre-assigned periods. The mostrecent computers used for dives with Nitrox cal-culate the oxygen exposure percentage basedupon the various depths at which the diversremain during the dives and display it to thedivers (usually with the “%CNS” symbol). You candecide to trust your computer of course, but youhave to read carefully the instructions and,should you reach 50% CNS exposure during 24hours rolling wait at 1 hour at least before divingagain. Never exceed 90% CNS exposure during 24hours rolling. Should it happen, don’t dive for 12hours at least.Signs and symptoms: low heart beats, palpita-tions, depression, anxiousness, false visualeffects (darkness, flashes, tunnel effect), hearingthe bells or other auditory hallucinations, verti-gos, irregular breathing, nausea, tremors andcontraction of lips, cheeks, nose, eyelids, blac-kout and convulsions (with serious risk of drow-ning).

Should you feel any of these symptoms, ascendwithout waiting, exit from the water and don’tdive for 24 hours, as a minimum.

Concurrent elementsOther elements can cause oxygen intoxication toCNS symptoms, such as medicines, tiredness, car-bon dioxide accumulation in the organism. MedicinesThe same considerations for dives with air applyto dives with Nitrox: avoid taking congestionrelief medicines before diving; should you betaking medicines, ask the doctor to get informa-tion. As you know, alcohol and drugs must beavoided before diving as well.Carbon dioxideAs demonstrated by some analysis, there is aclose connection between carbon dioxide concen-tration in the organism and oxygen intoxication.For this reason, remember to respect the rulesyou have learned during the ESA Open WaterDiver Course: breathe slowly, deeply and conti-nuously. Avoid holding your breath to save air;the most probable result would be a higher airconsumption and carbon dioxide accumulation.

Minitest1. The recharge for partialpressures is particularlydelicate because:a. the operator interactswith pure oxygen at highpressureb. the pure oxygen passesthrough the compressorand the tank valve c. a and b are exact

2. The components of therecharge station that usespure oxygen necessarilyhave to be:a. new b. "oil free"c. painted to yellow andgreen strips

3. To produce the Nitrox:a. it can be used any type ofoxygen b. it is had to use medicaloxygenc. it is not had to use medi-claoxygen

Answers:1 c; 2 b; 3 b

39

The latter exposes you to fatigue, decompressionsickness, nitrogen narcosis and oxygen intoxica-tion.Considering the limits for recreational dives usingEAN32 and EAN36, monitoring carbon dioxide isnot needed. Anyhow, as accumulating carbon dio-xide is subjective, should you usually have heada-che after diving, get in touch with a doctor awareof scuba diving related issues, reduce the exposi-tion to oxygen limiting the maximum PO2 to 1,4BAR and avoid holding your breath while diving.

Decompression sickness, arterial gaseous embo-lism and narcosisAs far as decompression sickness is concerned, allthat you have already learned during the ESAOpen Diver Course and subsequent still applies:breathing Nitrox reduces nitrogen absorption aswell as the decompression sickness risk; anyhow,a reduced risk still exists.To prevent the decompression sickness you needto plan your dives carefully, to respect the nodecompression limits, check the manometer fre-quently, analyse theNitrox mix to check theoxygen percentagebefore each dive, setthe computer properlyand respect all that youhave learned.As you know, should adiver have signs andsymptoms specific todecompression sick-ness, look for a doctor,check if he breaths andthat his heart beats andmake him breathe pureoxygen, if available,until the medical staffis available. Thedecompression sicknesscan be treated only inhyperbaric chambers by qualified personnel.As far as volume variations with depth and pres-sure are concerned, Nitrox and air behave thesame way: it decreases when going deep andincreases ascending.The arterial gaseous embolism is due to lungsoverstretching; to avoid it remember to apply the

2The full facemask can pre-vent the floodof the aerialstreets in caseof convulsions

40

most important rule you learned during your firstcourse: don’t hold your breath when scubadiving. The procedures in case of decompressionsickness apply to arterial gaseous embolism aswell.Nitrogen narcosis risk is reduced when divingwith Nitrox but oxygen has narcotic effects too.Therefore, should you feel a bit exuberant,remember it can be narcosis. Indeed, check yourand your mate lucidity often. In case of any unu-sual behave, ascend a bit and signs and symptomswill disappear.

Managing emergenciesHaving accident while diving is reallydifficult if your respect all the proce-dures and rules conscientiously; thisapplies also to Nitrox diving. Shouldan accident happen, this shall bemanaged as established in the ESAFirst Aid, Open Water Diver,Advanced Diver and Prevention &Rescue Diver manuals.Anyhow, should you see a diver faintwhile diving, and should divers morequalified than you be not around, tryto help him without risking yoursafety. Ascend with him, try to holdthe regulator in his mouth but,should he lose it, don’t waste timetrying putting it back. Ascendrespecting the maximum speed limitwithout hesitation. Once at the sealevel, trim him positively, open hisairways and, if needed, try to resu-scitate him; look for help withoutstopping checking that he breathsand that his heart beats, and ifnecessary, without stopping theresuscitation.

Should a diver have problems after having ascen-ded, look for medical help and, should he faint,apply the above. Once again, it is statisticallydemonstrated that the chances for a diver thatapplies conscientiously all the rules he learnedduring the courses and that respect all theinstruction provided by the equipment manufac-turer to have problems are very low.Anyhow, considering that people are not all thesame, neither learning methods nor tables can

Remember!• max PO2 1,5;

• maximum timefor single dive is 120minutes

• 180 minutes in the24 hours, if You aremaking multiple dives;

41

2

Breathes slowly,

deeply andcontinually,avoids with care toeffect micro-suspensions of

the respiraton.!

guarantee that problems are warded off.Furthermore, you could see an accident happe-ning by chance and being helpful is important.Therefore, continuing your training (you mayhave already done it) attending the ESA First Aidis important; this course can be attended by any-body. This course trains you to help people whodon’t feel well or victims of accidents. The ESAPrevention & Rescue Diver is a more completecourse and is specific to scuba diving; the prere-quisites for this course are: having the ESAAdvanced Diver (or similar) licence, have at least20 dives registered in your log book. Learningtechniques to held divers, specially providing oxy-gen in case of decompression diseases and tothose people who have risked to drown, is ofparamount importance.

42

Congratulations!Now you can plan your Nitrox dives and, duringyour next trip, you will be able to enjoy theadvantages offered by Nitrox. You may choose todive with Nitrox to feel less tired or to have timeenough to explore specific sites that, due to theirfeatures, could need longer no decompressionlimits than those for air.Ask the technician to apply all products and pro-cedure needed to make your equipment oxygencompatible and remember that, with the appli-cation of such products and procedure, yourequipment can stand 40% of oxygen maximum.Now you can provide general information aboutNitrox and how it is produced; you are able tochoose a professional recharge station too.Maybe you got a bit worried reading the para-graphs about effects of oxygen, decompressionsickness and narcosis; anyhow, you will haveunderstood that respecting the limits establishedfor recreational dives helps you in avoidingthem. Furthermore, being able to recognise signsand symptoms help you in preventing them.Having problems is quite difficult for consciousdivers anyhow, improving your training and kno-wledge attending first aid and rescue courses,will make you feel comfortable and aware; thelast paragraph provided you suggestions on theESA courses that can improve your preparation.The Instructor will give you the ESA Nitrox Diverlicence if you have attended the course, filled inand corrected the “What have you learned?”questionnaires and successfully completed thedives with Nitrox. Remember that you don’t needto wait for the sticker to apply to your licence toask the diving centres to dive with Nitrox. Forany questions you may have, don’t hesitate tocontact ESA; you can find the email addresses onthe web site www.esaweb.net

Minitest1. The due greatest dangerto the elevated concentra-tion of the oxygen breathedduring dive is:a. the nitrogen narcosisb. the poisoning from oxy-gen to pulmonary level c. the poisoning from oxy-gen to the CNS

2. To prevent hiperoxya:a. respect the limits of oxy-gen’s exposure b. to respect the limits ofdepth and PO2c. a and b are exact

3. The "CNS Oxygen Clock"it is:a. a particular analogicaltool for the Nitrox dives. b. a system of monitoringthe exposure to the oxygenof the CNSc. the clock used by thescuba divers professionals

4. The acronym CONVUTIVis used to remember:a. a particular procedure ofequipment’s controlb. the symptoms of the oxygenpoisoning of the CNSc. the formulas to plan theNitrox dives

Answers:1 c; 2 c; 3 b; 4 b.

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What haveyou learned?This exercise will let your review all the mostimportant information contained in this unit, sothat you can improve your preparation and beready for your next appointment with yourinstructor. Answer the questions choosing theright questions among the listed ones. Check youranswers with your Instructors; in case of any inac-curacy, he will provide all the needed explana-tions.

1. If compared with air, Nitrox:a. extends the no decompression limits b. doubles the no decompression limits c. enables you to ignore the no decompressionlimits

2. Diving with Nitrox and respecting the nodecompression limits applicable for diving withair (21% O2 / 79% N2):a. you avoid the decompression sicknessb. you absorb less nitrogenc. nitrogen narcosis is more likely to happen

3. How long can a 15-litre cylinder charged at 20BAR provide air at a depth of 25 metres if youbreathe at a rate of 20 litres per minute at the sealevel?a. 57 minutesb. 70 minutesc. 53 minutes

4. The cylinders for Nitrox must be properly mar-ked:a. to avoid wasting timeb. to prevent accidentsc. so that the end users don’t need to analyse it

5. Nitrox is produced:a. removing nitrogen from the airb. adding oxygen to the airc. both a and b

6. Combustions caused by a high concentration ofoxygen depend on

Minitest1. Nitrox breathing:a. removes the possibilityto have the MDDb. the MDD can equally berevealed c. you cannot verify anover lung pressure

2. The treatment for MDDand EGA also foresees:a the administration ofpure oxygen b. a physician's interven-tionc. a and b are exact

3. A datum volume ofNitrox, in a flexible contai-ner, during ascending it:to. it is unchangedb. it increasesc. it decreases

Answers: 1 b; 2 c; 3 b;

44

a. type of oxygen b. hydrocarbons and lubricants not compatiblewith oxygenc. flames

7. Oxygen intoxication to the whole body:a. is rare if the recreational divers respect theexposure limitsb. is mainly due to breathing oxygen high concen-tration for longc. both a and b

8. According to the NOAA tables (PO2 1,5 maxi-mum) the exposure to oxygen limits over 24 hoursrolling are:a. 120’ for a single dive o 180’ for repetitive divesb. 180’ for a single dive o 120’ for repetitive divesc. 100’ for a single dive o 120’ for repetitive dives

9. If you use a computer for Nitrox dives:a. read the instruction carefully b. don’t exceed 90% (CNS%) exposure to O2 over24 hours rollingc. both a and b

10. Oxygen intoxication to CNS can be caused by:a. the position of the diver during the diveb. a regulator that provides Nitrox too easilyc. an excessive CO2 accumulation

11. In case of decompression sickness after aNitrox dive, look for medical help, check brea-thing and heart beat and:a. provide pure oxygenb. don’t provide pure oxygenc. both a and b

12. Among the symptoms of oxygen intoxicationto CNS you can find:a. visual and auditory alterations, tremors of lipsb. pain, itchiness, tirednessc. high temperature, paleness, swelling

13. Hyperoxia susceptibility a. changes from person to personb. for the same person depends on the specificmomentc. both a and b

14. Convulsions are dangerous while diving as the

Minitest1. You can learn the techni-ques for managing an emer-gency during the course:a. ESA Prevention & RescueDiverb. ESA Advanced Diver c. ESA Ecodiver

2. The term PDD means:a. Pathologies from Decom-pressure b. Personal Diving Devicec. Pathologies from Descent

3. In case of emergency, itis important:a. to get as soon as possi-ble help physicianb. to establish the causes ofthe accidentc. to guess exactly thename of the pathology

Answers:1 a; 2 a; 3 a;.

45

victim:a. can hurt because of blunt instrumentsb. cannot be trimmedc. can drown

15. To avoid oxygen intoxication to the CNS:a. apply all rules for recreational dives in a strictwayb. respect depth and exposure to oxygen limitsc. both a and b

I declare that I have reviewed all the wrong answers with the ESA Instructor, and that I have understood the related explanation.

Signature ___________________date_________

2

Device tocheck theflow ofNitrox on thesensor of theanalyser

46

47

Open Waters 1 and 2BriefingListen to the explanation from the Instructor anddon’t hesitate to ask questions in case you needclarifications.Open Waters briefings are specifically importantas ascending to clarify something is not conve-nient for many reasons; listening to the briefingand have enough time to dive and practice theexercises and repeating them is much more profi-table. The Instructor will explain all you have todo – how and when – therefore putting on holdany other activity during the briefing and concen-trating on it only is of paramount importance.Again, should you need any clarifications, don’thesitate to ask questions: either the Instructor orthe Diveleader will help you.

Nitrox analysisYou will analyse the chosen mix together withyour mate and under the supervision of yourInstructor; this is needed to verify that the oxy-gen percentage indicated by the blender and iscorrect and compatible with the dive you haveplanned.Remember that any time you use a gas mixesother than air (oxygen percentage 21%), you willhave to analyse the mix using a suitable instru-ment connected to a flow-meter. Do it with yourmate: each one will analyse the content of hiscylinder under the supervision of both the othermate and of the Instructor.

Planning the Nitrox diveUse the ESA table for diving with Nitrox with yourmate, as indicated by the Instructor. To take themost of the profits by diving with Nitrox havingregards of safety, planning every dive carefully isof fundamental importance. Take the advantageof this exercise to improve your skill and solveany problems with your Instructor and your mate.Should anything appear not too clear or in case ofdoubts, don’t hesitate to ask the Instructor to cla-rify it: this is important for your safety. Shouldyou use a computer for Nitrox dives, verify thatthe oxygen percentage is correctly set.

CNS Oxygen Clock

2

48

Verify that you don’t risk exceeding or getting tooclose to the established oxygen exposure limit,taking into account previous dives.Oxygen intoxication to the CNS is an importantfactor to be considered when diving with Nitrox:don’t exceed the exposure limit of 120 minutesover 24 hours rolling for a single dive and 180minutes for repetitive dives.

Getting ready, checking the equipment and put-ting it onPrepare the equipment needed for the dive, askyour mate to help you putting it on; when youand your mate are both ready, check each otherequipment.As you usually do, you can assemble BCD andregulators on the cylinder and then verify that itis charged. The best way to put the equipment on maydepend on the specific dive: should you be on aboat you may decide to do it in the water (theinstructor will provide the needed information).As you know, checking the equipment beforediving is the best way to avoid equipment relatedproblems, so do it carefully. Should you discoverany problem, inform the Instructor or the Staff oryour mate. Check that the oxygen percentage isproperly set in the computer.N.B.: should the weather conditions and yourexperience be enough, at the discretion of theInstructor, you could check the equipment afteryou have jumped into the water.

Getting into the waterThe Instructor and the Staff will provide you theinformation for the best way of getting into thewater based upon the boat and the dive site. Besure you are positively trimmed and wait, toge-ther with your mate, indications from the Staff onwhen starting to dive and on the exercises to becarried out at the sea level.

Checking the correct quantity of ballastThis is an important check and must be donebefore starting to dive. Checking the correctquantity of ballast is important to be trimmed asneeded; being perfectly trimmed is importantwhile diving in to be more relaxed and to avidproblems to the environment. Furthermore, youwill be able to respect the established depth

49

limit. Get used to making this check to preventproblems due to an incorrect quantity of ballast.

DescentUse a rope or the seabed as a reference point anddon’t exceed the depth planned by the Instructor.This phase is really important, remember theMOD! Specifically, remember to descend togetherwith your mate, slowly, and checking either thecomputer or the depth gauge. All informationabout the best way to descend will be provided bythe Instructor during the briefing.

Diving respecting both plan and safety parame-ters.Check depth, time and manometer frequently andexchange the information with the mate. Diveone meter shallower than planned. You must take extreme care of depth when divingwith oxygen enriched mixes in order to avoid oxy-gen toxicity related problems. As you can divelonger, remember to check the time and themanometer. You should exchange informationabout the pressure in the cylinder with your mateevery 20/30 bars.

Exercised for other ESA coursesShould you attend the ESA Nitrox Diver course inconjunction with other ESA courses, practice theexercises for such other courses as explained bythe Instructor during the briefing. This doesn’tapply in case the ESA Nitrox Diver course is atten-ded as a stand alone course.

Repetitions and experienceRepeat the exercises under the supervision of theStaff. This will make you more familiar with theunderwater environment. Should and exercise notbe clear or you want to do it again, don’t hesitateasking the Staff.

Ascent and safety stopAscend slowly (not faster than 10 metres perminute) using a fixed point of reference and stopat 5 metres for 3 minutes. Ascending slowly andcomplete the safety stop is important for all kindof dives, included those with Nitrox. This enablesyou to improve safety and diving techniques. TheInstructor will provide the needed information.

3

50

Getting out of the waterDo it using the technique suggested by theInstructor.

Disassembling the equipment and taking care ofitIt is important and needed to keep your equip-ment, including the instruments needed fororienteering, efficient. Whenever possible, rinseit with fresh water even before disassembling it,then put it into your sack to wash it when sugge-sted by the Staff.

DebriefingListen to the comments the Instructor will have.This is another way of improving. Don’t do any-thing else but listen to the Instructor during thebriefing. He will have useful comments on youperformance, suggestions and recommendations.Take the opportunity to improve further anddon’t hesitate to ask questions.

Registering your diveFill in your logbook and ask your Instructor to signit. This is needed to confirm your open water trai-ning. Register all parameters (such as the CNSoxygen clock), the environmental conditions andthe exercises, plus your personal comments.

Remember to ask the Instructor to sign.

51

9 rules for diving with Nitrox1. Use proper and efficient equipment; make sureit is regularly maintained

2. Analyse the oxygen personally

3. Make sure the oxygen analyser works properly;respect the instruction provided by the manufac-turer and make several trials with air, pure oxy-gen (if available) and then the Nitrox mix.

4. Respect the Maximum Operative Depth: don’texceed 31 metres with EAN 36 and 36 metres withEAN 32

5. Set correctly the oxygen percentage in the com-puter or choose the right column in the table ESA“EAN 36 – EAN 32 – AIR DIVE TABLES”: the wrongoxygen percentage can cause decompression sick-ness or iperoxia

6. Make sure the computer is properly set beforeeach dive: get used to check both and your mateinstrument before diving

7. Respect the limit of 120 minutes for a singledive and 180 minutes for repetitive dives over 24hours rolling. Don’t dive more than 3 times a daywith Nitrox: this simple rule helps you in preven-ting helps you in preventing oxygen intoxications.Should you get close to the limits, don’t dive for12 hours at least.

8. Breath continuously without holding yourbreath and prevent breathlessness: carbon dioxi-de accumulation can cause hypoxia. So avoid hol-ding your breath while diving, try not to getweary and use a good performance regulator

9. Respect your license and local rules depth limit:the ESA Nitrox Diver license doesn’t enable you todive deeper. You must comply with the limitationsof your preceding license (i.e. ESA OWD = 18metres).Remember to consider the limitations cause byPO2. The CNS% value per minute must be multi-plied by the minutes spent at a certain depth.

3

52

Appendix ESAESA is a didactic agency and his/her principalobjective it is that to form the scuba divers fromthe initial level up to the attainment of the pro-fessional levels as Diveleader and Instructor. Todo this the ESA is established to jointly apply themost evolved operational standards to an eleva-ted safety degree and to promote the underwa-ter activity in his/her various forms. The formative runs of the ESA foresee the infor-mation integration divulged by the instructorwith the materials of support that accompanythe various levels of brevet. Initial practical formation happens with thedevelopment of the underwater abilities in swim-ming pool or delimited basin, subsequently youapply and you improve in free waters. For every program or raced ESA it is anticipateda verification of the learning from the instructorthat will have to preserve a test of the happenedevaluation. The scuba divers can receive from the ESA theinitial formation, to progress toward taller levelsof brevet, to specialize himself/herself/themsel-ves in different areas tied to the underwateractivity as the sea biology, the photo, the under-water archaeology, etc. Reached adjust her credential, the scuba diverscan participate in the programs for the forma-tion type professional within the underwateractivity. The esa establishes elevated standards for theformation of his/her own affiliate: they is under-water professionals in possession of a brevet ESADiveleader or of taller degree. The preliminary ESAs are formed from the ESAsIC Director, prepared and qualified people ade-quately to transmit the techniques of teaching tothe preliminary future. The formation of the instructor is complete andforesees the acquisition of information on thetheory of the immersion, on the procedures ESA,notions of psychology and marketing, the deve-lopment of the abilities of management of thesingle scuba divers or in group, of managementof the problems, of safeguard of the environment

53

and other. The validations of the brevets ESAs are issuedfrom the central center and from the offices ESAofficially authorized. The department ESA that deals him with the for-mation informs the affiliate ESAs on the varia-tions of the existing procedures and on the intro-duction of new procedures. You/they can also join to the ESA qualified struc-tures that operate in the field of the recreationalunderwater activity. Immersion centers, underwater club and younegotiate su bacquei they are able, in fact, toacquire the qualification of ESA Point. The deno-minated structures ESA IC Point can promote, toorganize and to conduct the courses of formationfor the Preliminary ESAs. The esa intends to also characterize him througha particular facing appointment the populariza-tion of the knowledges on the environment, toimprove the quality of the immersions and tocreate in the su bacqueis a greater awarenesstoward the submerged space. The professionalsESAs, in fact, effect their formative run alsoreceiving a solid preparation on the knowledgesrelated to the environment. the whole formativeactivity of the ESA is firmly connected to objecti-ve of safeguard of the aquatic environments.

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9 Suggestions to preserve theaquatic environmentIf you follow these simple rules you will give a great con-tribution to the preservation of the aquatic environ-ment.

1) Control your buoyancy at all times. If you are neu-trally buoyant you will avoid damages to the sea floorand its inhabitants. If you don’t wear gloves you will beless inclined to touch and feel about the sea floor, cau-sing possible damages.

2) When you approach the bottom don’t flap yourhands and fins around. If you have to rest on the bot-tom, make sure your knees and fins don’t cause anydamage.

3) Avoid tunnels and caverns, by touching their ceilingyou could damage the life living on them, besides yoububbles could not escape and turn the top of a cave intoa submerged desert.

4) Don’t hold on to sea turtles, large fishes and seamammals, just swim with them but don’t chase the ani-mals, they might not enjoy it as much as you.

5) Try not to touch animals you don’t know. You mightget hurt or remove their protective mucus making themmore vulnerable.

6) Do not remove anything from the bottom, shells (nei-ther dead, nor alive), algae covered objects or archaeo-logical finds.

7) Do not buy souvenirs made with shells or other mate-rials coming from the sea. It a way to discourage theircollection or fishing.

8) Do not litter the sea. Use the rubbish bins.

9) Carry on your training and extend your knowledge ofthe marine environment, you will discover that everylocation deserves a dive and that every environmenthas amazing discoveries to unveil.

All the inhabitants and the visitors of the underwaterspaces thank you in advance for your effort

55

MiscellaneousID’sDive LicenceLog bookReservations/ticketsEmergency contactsSwim suitSun screenSun glassesHatWind breakerTowelBath robeSandalsGoggles and bathing capSpare clothingFood and drinksMedicines

EquipmentBagFins, mask and snorkelWet suitThermalsHoodGlovesBootiesWeightsBCDFull cylinderMain regulatorSpare regulatorPressure gaugeBCD pipeDry suit pipeKnife

InstrumentsDive computerDepth gaugeTimerCompassThermometerDive tables

AccessoriesDive slateAnimal guidePencilDive buoySurface signalling deviceReelMain torchSpare torchStrobe lightPosition indicator lightSnap-hookAnti fog spray/liquidEquipment lanyard

Spare gearO-ringCylindersWeightsStrapsTool kitWet suit repair kit

Special equipmentUnderwater cameraLens and zoomsFlashFilmsVideo cameraHousingTapesVideo lightsBatteriesBattery chargerWiring and connector

Notes__________________________________________________________________________________________________________________________________________________________

Not to be left at home

56

Conversion table from meters to foot(1 meter = 3,28 foot)

METER

FOOT 39 49 56 59 66 67 75 79 85 88 92 98 102 108 112 118 131

12 15 17 18 20 21 23 24 26 27 28 30 31 33 34 36 40

PO2 Table and O2 exposition limitsfor Dives with NITROX as per NOAA rules

(National Oceanic & Atmospheric Administration)

EAN 36meter

34

31

28

26

23

20

17

15

12

40

36

33

30

27

24

21

18

15

1,6

1,5

1,4

1,3

1,2

1,1

1,0

0,9

0,8

2,22

0,83

0,65

0,56

0,47

0,42

0,33

0,28

0,22

45

120

150

180

210

240

300

360

450

150

180

180

210

240

270

300

360

450

EAN 32meter

Single exposure

1 divewithin 24 hours

Multipleexposuremore dives

within 24 hours

CNS %for minute

PO2

ATA

TABLE CONVERSION MEASURES OF PRESSURE

1 PSI (pound x square inch) = 0,073 kg x cm2

1 atm = 1,033 kg x cm2

1 atm = 14,696 PSI

1 kg x cm2 = 14,223 PSI

57

Pg = Partial pressure of a gas to a certain depth

* Fg = Fraction of the gas or partial pressure of the gas in surface

in meter [(depth + 10) : 10] x Fg = Pgin foot [(depth + 33) : 33] x Fg = Pg

EAD = equivalent depth in airin meter [(FN2 X depth + 10) : 0,79] - 10 = EADin foot [(FN2 X depth + 33) : 0,79] - 33 = EAD

MOD = Maximum operational depthwith limit PO2 to 1,5in meter [(1,5 x 10) : FO2] - 10 = MOD in foot [(1,5 x 33) : FO2] - 33 = MOD

Here are the formulas!They are more' simplethan it seems.Test to apply its...

58

15 5

39

33

21

15

10,5

9

12

18

24

30

36

7,5

27

* Single dive maximum timewith EAN x: 120 minutes

* Tempo massimo per immersione singola

con EAN x:120 minutiA B C D E F G H I J K

A B C D E F G H I J K

36

29

22

28

12

20

15

11

7,5

25 50

110 120*

8 6

35 70 110 120*

20 35 55 75

5 15 25 40

10 15 25

5 10 15

5 10

6,5 4,5

9

13

10

13,5

17

24

26

31

32

18

ProfonditàDepth

EAN 36m

ProfonditàDepth

EAN 32m

ProfonditàDepth

AIRm

EAN 36 - EAN 32 - AIR DIVE TABLESNo- Decompression and O2 Exposure Limits - Repetitive Group Designation

Tables for No-Decompression Dives

EANxTABLE 1

Gruppo di Appartenenza / Pressure Group

5 10 12

20 30 35 40

30 40 50 60

50 60 80 100

100 120*

13 15

5

120*

70

15 20 25

5 10

5 7 10

5 10 15

10 15 20

15 25 30

15 30 45 60

40 50 70 80

25 30 40 50

75 110 120*

75 95 120*

20 25 30

15 20

100

EAN ___ EAN ___

59

EANxTABLE 2

EANxTABLE 3

New Group Designation

Warning: These tables mustbe used by certified divers orunder the direct control of acertified scuba instructor

Residual Nitrogen Time (Minutes)

Tempo totale massimo per immersioni consecutivenelle 24 h = 180 minutiMaximum total time for ripetitive dives within 24hours = 180 minutes

Adjusted No-Decompression Time Limit

Rip

etiti

ve D

ive

Dep

th

Pro

fond

ità I

mm

ersi

oni C

onse

cutiv

e

Product N° A0039

A

B

C

D

E

F

G

H

I

J

K

A B C D E F G H I J

0:100:00

3:2112:00

0:103:20

6:3512:00

3:256:34

1:583:24

0:551:57

0:461:29

1:302:28

0:100:45

0:100:36

4:5012:00

1:404:49

0:101:39

7:0612:00

3:587:05

2:293:57

1:161:59

2:002:58

0:411:15

7:3612:00

4:267:35

2:594:25

5:4912:00

2:395:48

1:102:38

0:101:09

0:100:54

0:100:40

1:422:23

2:243:20

1:071:41

8:0012:00

4:507:59

3:214:49

0:371:06

0:340:59

0:100:33

2:032:44

2:453:43

1:302:02

8:2212:00

5:138:21

3:445:12

1:001:29

0:551:19

2:213:04

3:054:02

1:482:20

8:5112:00

5:418:50

4:035:40

1:201:47

0:100:31

0:320:54

0:501:11

0:290:49

1:121:35

2:393:21

3:224:19

2:042:38

8:5912:00

5:498:58

4:205:48

1:362:03

6

9

6

9

13

17

20

24

28

31

12

15

18

21

24

27

33

30

5 3

8

12

15

18

22

26

29

32

36

36

39

39 88 159 279

18 39 62 88 120 159 208 279 399

12 25 39 54 70 88 109 132 159

7 17 25 37 49 61 73 87 101

6 13 21 29 38 47 56 66

116

190

5 11 17 24 30 36 44

4 9 15 20 26 31 37

4 8 13 18 23 28

3 7 11 16 20 24

3 7 10 14 18

3 6 10 13

3 6 9

3

* * * * * * * *

* * * * * * * *

120 113 105 93 81 69 57 43

64 57 49 41 32 23 14 4

45 39 33 26 20 14

36 31 25 20 14 9

26 22 17 12 7 2

22 18 14 9 5

17 13 10 6

12 9 5

7 4 1

2

* * **

3939

*

2

2

1

3

6

*

* *

29 14

EAN 36 EAN 32 AIR

Ripetitive Group atthe Beginning of

the Surface Interval

Gruppo diAppartenenza

all’inizio dell’inter-vallo di superficie

O2 analysis

Switch on the tool and waitsfor some minutes that thesensor environments itselfand correctly measure thepercentage of ox

Note: all the connectionsmust be completely taghtinup included the attacks to thesensor and to the tool

Body of the sensor

Plastic T join

Terminal of the sensor

Flow regulator for DIN valve

Example of system for O2 analysis

61

1.Connectionof the regu-lator offlow to theDIN valve2.Graft of thelink to T onthe regula-tor of flow3.Is impor-tant toscrew wellthe ferruleof connec-tion of thesensor tothe cable ofthe tool 4.Insertion ofthe sensorin the spe-cial lodgingin the link TO T5.The proce-dure mustbe madefirst on acylinderwith air,setting Iorchestratehim/it on 216.The proce-durerepeats himon the cylin-der with theNitrox. Thereadingdoes effec-ted whenthe datumstabilizeshim

1 2

3 4

5 6