Emergency Response Procedures forAnhydrous Ammonia Vapor Release

A detailed review of downwind ammonia vapor adsorption tactics, developedfor firefighters. A major contribution to ammonia plant safety.

Maurice L. Greiner, J. R. Simplot Co., Pocatello, Idaho

Anhydrous ammonia is a material normally handled underpressure. When it is released following an accident or priorto a threatened release from vessels weakened by over-heating, mechanical damage, or some other cause, down-wind defense and rescue work become a high priority. It isessential that fire fighters and other emergency-responsepersonnel understand the characteristics of this material,now to protect themselves, and what can be done,to controlthe situation.

In this paper, I shall review some downwind ammoniavapor adsorption tactics we have developed for firefighters as the result of several hundred outdoor ammoniaworkshops we have conducted throughout the WesternUnited States and Canada over the past several years. Ishall also examine the effectiveness of fire fighter'sturnout clothing to provide body protection in ammoniavapor.

COMMON AMMONIA CHARACTERISTICS

A review of the basic characteristics of ammonia is es-sential if we are to discuss personal protection and vaporcontrol techniques.

Ammonia is caustic to human flesh, especially the mu-cous membranes and eyes. High levels of ammonia canproduce corrosive effects on tissues and can cause laryn-

feal and bronchial spasm and edema so as to obstructreathing [2]. At atmospheric pressure and ambient tem-

perature the vapor is colorless. However, when first re-leased from a liquid line or ruptured vessel the vapor is vis-ible in the form of a white fog due to the condensedatmospheric moisture.

The ammonia vapors are usually lighter than air; how-ever, their dispersion will also depend on other factorssuch as wind, sunlight, temperature, humidity, and type ofrelease [3].

The pungent odor of ammonia makes it an effectivewarning agent when released into the atmosphere. Con-centrations as low as 5-10 parts-per-million can be de-tected by some persons. However, persons who regularlywork with ammonia may have difficulty detecting it inconcentrations less than 50 ppm. In accordance with thecurrent United States federal standard an employee's ex-posure must be limited to a concentration not to exceed 50ppm of ammonia in air by volume based upon an 8 hour,time-weighted average. Concentrations from 150-200 ppmwill cause general discomfort and eye tearing. At 400-700ppm the irritation to the eyes, ears, nose, and throat is moresevere. Exposure to concentrations over 2000 ppm willburn and blister the skin and produce serious edema,strangulations, asphyxia, and death within minutes [2].

Ammonia is classified by the United States Coast Guardas a non-flammable compressed gas for the purpose oftransportation (in Canada it is classified by the CanadianTransport Commission as "poison gas"). However, the po-tential always exists for explosion where there is a high ig-

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ration source and the ammonia-air mixture happens to bein the correct proportions. This ignitable confinement ismore likely to be encountered when ammonia is releasedinside a structure than in an outdoor situation where windcurrents and vapor dispersement are at work.

CONSIDERATIONS FOR DOWNWIND CONTROL OF AMMONIAVAPORS

Because of their usual buoyancy and generally lighter-than-air characteristics, ammonia vapors cannot be effec-tively absorbed by water fog or spray nozzles directed fromupwind. The pressure from even one water fog nozzle maybe enough to drive the harmful vapors downwind morequickly. This is of no serious consequence if the down-wind area is entirely free of humans, animals, schools, hos-pitals, residences, and traffic. But this is not usually thesituation.

The major concern to emergency response personnelarriving upon the scene of an accidental release is to res-cue and evacuate persons from downwind areas and to setup a downwind defense system to relieve the situation. Ahigh priority must also be given as the same time tocontrolling the source of the leak.

Accidental releases of ammonia occur from a number ofcauses: 1) overfilling of tanks, 2) damaged or overturnedtanks or rail tank cars, 3) venting of excess vapor, 4) failureof loading or unloading lines, 5) failure of relief valves, and6) pipeline failure.

SOME CASE HISTORIES

Forty tons of liquid ammonia were released from a tankcar when the driver failed to disconnect his liquid lineafter filling his truck from the rail car. The release of am-monia from the tank car was finally controlled when emer-gency personnel could get on top of the car and shut off theliquid valve.

In the dome assembly on ammonia tank cars, there aretwo liquid-withdrawal valves. The interior pipes on thesevalves extend practically to the bottom of the tank and areused for the withdrawal of the gas in its liquid state. Thevapor eduction or withdrawal valve is positioned towardsthe side of the tank car and is used for the withdrawal ofvapor or to pressurize the car so the liquid may be pushedout through the liquid lines. Both the liquid valves and thevapor valve turn clockwise to close. This knowledge is im-portant in the event of an emergency. Most ammonia leaksoccur in the dome assembly on these tank cars.

A local freight train collided with a tractor-trailer rigwhich was transporting approximately 41,000 pounds(16,600 kgs) of anhydrous ammonia. The impact knockedthe tractor-trailer rig approximately 300 feet (90 meters)down the road, tearing a hole in its shell.

A cloud of ammonia vapor was released from the rup-tured tank downwind. Three people died in that ammoniatruck crash, but many more would have died had it notbeen for the quick response of fire and police officialswho rescued victims trapped in the ammonia cloud anddissipated the ammonia vapors with water fog.

A 500-gallon (1893-liter) ammonia nurse tank rupturedbecause the owner of a tank replaced the leaking safety re-lief valve with a solid plug. He filled the tank full, leavingno room for vapor expansion. The weather was warm andshortly after he filled the tank, it ruptured violently. Thehead of the nurse tank blew out when the tank ruptured.The tank itself flew about 300 yards (275 meters) fromwhere it had been sitting.

PERSONAL PROTECTION

Whatever the cause of the release of the vapors, the basic Figure ,. Fire fighters wearing full turnout gear and self-contained,need for rescue, evacuation, and vapor control is para- positive-pressure breathing apparatus have good protection in ammoniamount, and the responding fire fighters must know how vapors.

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to protect themselves in this environment while per-forming these tasks.

In the chemical industry we have learned to dependupon materials such as rubber, PVC, nitrile, and neopreneto protect our bodies, hands, and feet from 'the irritating,caustic, and freezing effects of ammonia. Positive pres-sure, self-contained breathing apparatus will provide res-piratory, eye, and face protection from ammonia vapors.

However, not all fire fighters responding to this type ofemergency will have industrial protective apparel, andonly a very few will have hazardous environment protec-tion suits which totally encapsulate a person.

But, the fire fighters in the Western States and Canadawhere we have conducted hundreds of outdoor ammoniaworkshops have demonstrated the effectiveness of theirturnout garments in heavy concentrations of ammonia.

Turnout coats and bunker pants are constructed with avapor barrier and heavy outer shell. High collars provideneck protection; tight-fitting wristlets enclose and protectthe arms from water entry; heavy fasteners secure extrathick, exterior mounted storm flaps to offer superior watershielding properties; fire fighter s boots and neoprene orrubber gloves protect feet and hands; and helmet and self-contained breathing apparatus provide head, face, and res-piratory protection (Figure 1).

With the backup of water fog and this type of clothingprotection the fire fighter is well equipped to performrescue work and ammonia vapor control.

Water is the main tool to use to absorb and control ammo-nia vapors. It is also necessary to minimize the effects ofammonia on the skin. It is therefore a mistake, I believe, toencourage fire fighters to cover their bodies with greaseor salve in an attempt to provide "barrier" protection. Thegrease or salve is a very fragile barrier at best and is easilyrubbed off areas such as the armpits and crotch by thewearer's clothing. These are among the most vulnerablebody areas for ammonia irritation and burns.

If a fire fighter's clothing is not closed properly and am-monia vapors gain entry and begin to irritate these grease-covered areas, the neutralizing benefit of water is greatlyrestricted.

In many hundreds of ammonia training exercises I haveconducted, only a very few firefighters experienced anyskin irritation from ammonia vapor and this was usuallyaround the neck area. This was always quickly and easilyrelieved on the spot by the application ofwater from a hoseline. Salve, ointment, or grease is not necessary and greatlycomplicates first aid treatments.

When ammonia is released its vapors moves easilydownwind. In a pressurized release it will move morequickly and in a cone-shaped pattern. To effectively re-duce the downwind movement of these vapors by absorp-tion and water pressure, fog nozzles should be positioneddownwind from the point of release.

One and one-half inch (3.8 cm) or 1-3/4" (4.4 cm) lineswith fog nozzles are ideal for downwind control. Severalimportant factors are: the distance of the nozzles from thepoint of release, the fog pattern, nozzle gallonage, pres-sure, and nozzle rotation. It has been demonstrated in nu-merous ammonia vapor control exercises that a "capture"zone can be created downwind by positioning the nozzlesin a semi-circle pattern (Figure 2) and allowing the ammo-nia vapor to drift into this pocket.

Distance is important because, for example, if the noz-zles are too close to the point of release they will, by theirown pressure, distort the ammonia cloud and push it back-wards, upwards, and beyond the control zone, and perhapseven into areas which they are trying to protect such asroadways, residential areas, etc.

We have found by experience that 75 to 100 feet (23 to 30meters) is a very good working distance from the point ofrelease in normal wind conditions [5 to 15 mph (8 to 24km/hr)]). In higher winds nozzles can be positioned asclose as 50 feet (15 meters). Nozzles should be located ap-proximately at the nine, eleven, one, and three o'clock po-sitions downwind for effective control. The eleven andone o'clock positions can be backed up by several addi-tional lines and nozzles if necessary to absorb vaporswhich may get by them.

Rotation of nozzles is essential, and by that I mean arapid and wide rotation (Figure 3) in clockwise and coun-terclockwise patterns. For example, facing towards thepoint of ammonia release, the nine and eleven o'clock noz-zles should be rotated in a counterclockwise pattern andthe one and three o'clock nozzles in a clockwise pattern.This greatly increases the effectiveness of the nozzles' am-monia absorption capabilities, at the same time creating avortex which will draw the lighter ammonia cloud into the"capture" zone for absorption and elimination.

To ensure that the ammonia cloud keeps moving down-wind against the water fog nozzle pressures, we usuallyfound it advantageous to set up two fog hozzles upwind,one on either side of the point of release. These nozzles,also rotated clockwise and counterclockwise, will createadditional pressure to keep the ammonia vapor clouddownwind into the "capture" zone. They also will absorb

Figure 3. Rapid and wide rotation of fog nozzles increases the efficiency ofammonia absorption downwind.

ammonia vapors on the periphery of the cloud, and pro-vide protection for the pumper and operator which mustalways be positioned (Figure 4) upwind from the point ofammonia release.

Wind conditions will effect the type of fog pattern to beused. For example, downwind nozzles will have to havetheir pattern narrowed to possibly a 30° pattern in highwind conditions. In low wind conditions a 40° to 45° pat-tern is very effective for ammonia absorption.

We have also observed that the absorption efficiency(Figure 5) of the fog nozzles is increased as the water pres-sure at the nozzle inlet and the volume of the ejected waterare increased. However, when the nozzle pressure was in-creased, we found that the nozzle distance from the pointof release also had to be increased slightly and our semi-

Figure 2. Fog nozzles positioned downwind in semi-circle pattern create aneffective pocket or "capture zone" to absorb ammonia vapors and protect Figure 4. Positioning of nozzles is important for control and containment ofdownwind areas. ammonia vapors.

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Figure 5. Large hose lines are needed to supply smaller handlines down-wind with sufficient fog nozzle patterns.

circle or "capture" zone widened so as not to distort theammonia vapor cloud.

When there is an ammonia pressure release with little orno wind conditions, it is necessary to set up fog lines in a360° circle, maintaining a distance of approximately 100feet (30 meters) from the point of release and rotating thenozzles so as to keep the vapor release contained and toachieve maximum absorption.

Downwind defense against ammonia vapor can also beachieved with certain types of vertical water screens. Onesuch unit, developed by a Canadian fire department [4] iscalled a "fan tail" (Figure 6). It utilizes a 2%"(6.4-cm) hosecoupling with a metal plate on the open end of the cou-pling that acts as a baffle to the water supply. The end ofthe coupling has a number of saw cuts on it to throw out thewater in a semi-circle vertical pattern.

The curtain of water produced (Figure 7) can reach ashigh as 35 feet (15 meters) and extend 50 feet (15 meters)horizontally. If placed 30-40 feet (9-12 meters) from thepoint of ammonia release, it is very effective in absorbingthe ammonia vapors passing through it without distortingthe ammonia cloud.

This homemade device is a useful piece of equipmentfor response teams to have on hand should they be calledupon to respond to ammonia emergencies.

In our exercises involving water curtains, however, wehave found it advantageous to have several fog nozzles far-ther downwind behind the curtain to absorb the remainderof the vapors getting through. These nozzles should be farenough downwind so as not to push the vapor cloud be-

Figure 6. A "fan-toil" unit like this positioned downwind can provide aneffective water curtain against ammonia vapors.

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Figure 7. A water curtain positioned downwind from an ammonia releasewill absorb large volumes of vapor.

yond the control circle. Rotation and placement of nozzlesis critical for good containment and absorption.

But, absorbing the ammonia vapors is only part of theemergency action. Rescue and evacuation from downwindareas may be necessary, and valves may have to be shut offto stop the ammonia flow. Wearing full turnout gear andself-contained breathing apparatus, fire fighters canmove in and perform these tasks. Water fog protectionshould be provided when they do this, however. Also, ap-proaches should be made from upwind whenever possibleto minimize exposure and to provide better visibility.

Following an entry into ammonia vapors, fire fightersshould be watered-down with hose lines to neutralize anyammonia which might be on exposed skin areas such as theneck and wrists.

After the ammonia release has been shut off, firefighters should continue washing the air downwind withwater fog to remove all ammonia vapor.

Summarizing down wind ammonia vapor control tactics:1. Evacuate persons who are downwind in the path of

the vapor release and rescue trapped victims. Imme-diately apply water to ammonia burns and administerartificial respiration where necessary. Apply firstaid care and get medical attention.

2. Position fire pumpers upwind and lay out large di-ameter hose lines to supply strategic downwind noz-zle positions.

3. Control vapor release by valve closure and absorp-tion of ammonia vapors with water fog.

4. Do not advance the fog nozzle onto the point of re-lease but allow the ammonia vapors to come into thewater fog patterns created downwind.

5. Rotation of fog nozzles increases absorption effici-ency.

6. Wear turnout clothing and respiratory protection.

REDUCING POTENTIAL VESSEL RUPTURE

When an ammonia tank is derailed or overturned andthere is no release of product, there is a great danger of adelayed failure or rupture of the tank. There have beenseveral instances of tank cars which have sustained dam-age in derailments and then subsequently ruptured. Someof these delayed ruptures have occurred as long as 48hours after the damaged car has been put upright.

Some of the main causes for tank car or cargo tank fail-ures are: mechanical damage such as denting or gouging,overheating of local areas of a tank from sliding along con-crete or the rails, or fatigue cracks in the metal itself. Themost common cause for delayed rupture is from mechani-cal damage. When a dent is created in a tank there is a cer-tain amount of recovery or dent removal by the pressure inthe tank car when the indenting object is removed. As the

dent is removed, a plastic tensile strain is imposed in thecold-worked layer in the gouge. This can cause the cold-worked material to crack, increasing the likelihood of rup-ture. The greater the notch depth, the lower the failurepressure. This also applies to dent depth. The addition of adent to an axial gouge greatly reduces the failure pressurein a tank car. Defects of this type can continue to creep tofailure when held at constant pressure [5]. Emergency per-sonnel should always inspect derailed tank cars or over-turned tankers on the highway for mechanical or physicaldamage, even if there is no release of product in the acci-dent. Any dents with gouges, grooves, or scrapes should because for concern and the p*ossibility of a delayed rupture.Extreme caution should be used in approaching a loaded,damaged tank car to inspect or unload it.

A damaged but still loaded ammonia tank must bedepressurized. One of the ways this can be done safelywithout adding unnecessary stress to the vessel is to open avapor valve. At the same time set up fog lines downwind toabsorb the ammonia vapors that have been given off. Asthe ammonia vapor releases from the tank car it will causethe tank car to slowly refrigerate and the pressure to drop,thereby relieving the danger of a delayed rupture. Thewater fog that is set up downwind should be far enoughaway from the point of release so as not to allow the waterto come in contact with the tank itself. Water coming intocontact with the tank would offset the refrigeration effect.A reminder that the fog lines which are set up downwind toabsorb the ammonia vapors must be operated in a rotationpattern for effective absorption of the ammonia vapors.

If a large water tank or reservoir is available nearby, thevapor could be directed through hose lines or pipes intothe water for absorption. Vertical water curtains could alsobe set up downwind to absorb the vapor.

FIRE

Ammonia liquid has a high coefficient of expansion,and as the liquid in a tank is heated-up, there is a rapid risein pressure. This is especially true if the ammonia tank isthreatened by fire. In this case, use water fog to try to keepthe tank cool to prevent it from rupturing. When applyingwater fog to a tank that is threatened by fire, always ap-proach from the side. The head of a tank will usually rup-ture first. If it appears that a fire is out of control and that atank is going to rupture, the area should be evacuated for adistance of 2000 feet (600 meters) in all directions.

LIQUID SPILLS

If ammonia liquid has been released onto the ground,the pool should be diked as soon as possible or divertedinto a holding area. This will help to stabilize the ammonialiquid pool [6]. Water fog nozzles can be set up downwindto absorb the ammonia vapor drift. Great care should betaken not to direct water into the ammonia liquid itselfsince this will cause rapid and vigorous boiling and vapori-zation of the cold liquid, thereby making the situationmore dangerous and increasing the ammonia vapors beinggiven off.

FIRST AID

Serious injury can result when water is not immediatelyapplied to ammonia burns. The use of ointment, oil, orsalve is prohibited, since it prevents the neutralizing effectof water. The burned area should be flushed or irrigatedwith water for at least 15 minutes. Contaminated clothingshould be removed as far as practical. Because of the freez-ing action of anhydrous ammonia, clothing may be frozento the skin, in which case thaw with water first. Keep thevictim warm and get him to a physician. If breathing has

stopped, begin artificial respiration immediately and ad-minister oxygen.

Eyes that have been contacted with ammonia will closeinvoluntarily and must be forced open to be flushed. Fail-ure to irrigate eyes contacted by ammonia can result in se-rious and irreparable damage.

SUMMARY

Emergency response to ammonia releases will usuallyinvolve the fire service. They have equipment and re-sources essential for ammonia vapor control. It is thereforeimportant that they receive training. Local dealers andmanufacturers of ammonia can help by providinghands-on training and site inspection opportunities. Firefighters should examine the valving at these locations,available water supplies, and access routes for fire equip-ment. Ammonia accidents can also occur in transpor-tation. Wearing protective clothing and respiratory equip-ment, the fire fighters must give priority to rescue of vic-tims caught in any ammonia release and the evacuation ofdownwind areas. Fog nozzle defenses can also be set updownwind to absorb and reduce vapors and to protecthighways and residential areas. Priority must also be givento the immediate treatment of ammonia burns with water.

To further assist emergency response personnel the De-partment of Transportation has published the "1980 Haz-ardous Materials Emergency Response Guide Book".With the aid of its indexing system, emergency responsepersonnel can quickly identify the hazardous material in-volved in an emergency. In this case, anhydrous ammonia,Guide 15 in this guide book gives the fire fighter somebasic emergency procedures to follow with the anhydrousemergency.

CHEMTREC, 800-424-9300, is a vital communicationlink for emergency personnel responding to ammoniaemergencies. Through CHEMTREC, fire fighters canquickly get in touch with manufacturers or shippers of thisproduct and obtain help for ammonia emergencies.

CHEMTREC is also available from points outside theUnited States, 202-438-7616.

Also, in case of a transportation emergency in Canadainvolving a compressed gas such as ammonia, the Cana-dian Chemical Producers Association had developed theTransportation Emergency Assistance Plan, commonlyknown as TEAP. Assistance is available for emergencypersonnel at the emergency scene through TEAP emer-gency assistance plan.

The Canadian government has also established the Ca-nadian Transport Emergency Centre, CANUTEC, to pro-vide emergency information for chemical spills and toserve as a communication link to shippers and manufactur-ers. CANUTEC can be contacted in Canada, day or night,at 613-996-6666.

Armed with knowledge and skill, ammonia emergenciescan be approached with confidence.

LITERATURE CITED

1. "Anhydrous Ammonia Plant Operating Manual," AmericanOil Company (1976).

2. "Handbook of Compressed Gases," Second edition, VanNostrand Reinhold, New York (1981), p. 220.

3. "Hazardous Materials Spills Handbook, Part 4," McGraw-Hill, "Part 4, Ammonia," Phani Raj.

4. Brandon Fire Department, Brandon, Manitoba, Canada.

5. Eiber, Robert J., "A Review of Some Tank Car Failures, WhatAre They Telling Us," Battelle Columbus Laboratories.

6. Husa, H. W. and W. L. Buckley, "Hazard of Liquid AmmoniaSpills from Low Pressure Storage Tanks," American Oil Com-pany, Whiting, Indiana.

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Maurice L. Greiner was a former professional foefighter for the City of Regina, Saskatchewan, Can-ada, 1952-1966 and a former Director of the ReginaEmergency Measures Organization 1966-1968 be-fore joining the Simplot Company in 1968.

He received his Fire Engineering Degree in1968 from the Institution of Fire Engineers. Hewas cited for bravery in the fire service April 23,1966. He received the Queen's Commendation forBrave Conduct, the "Life of Alberta Gold Medal",and the "Royal Canadian Humane Association'sCertificate for Bravery". He is an accredited FireService Instructor with the Oregon Fire Standardsand Accreditation Board.

He has written a training manual and produced5-hour workshops for fire departments on emer-gency procedures for fertilizers and ag chemicals.

He has conducted many hundreds of workshopsfor fire departments throughout the U.S. and Can-ada on fertilizers and ag chemical. He co-authoreda safety and health manual for the phosphate in-dustry in 1980 and has authored numerous articleson fire safety in fire and safety trade journals.

He developed and continues to direct the Inter-national Fertilizer Safety School, held annually inSpokane, Washington.

He was one of the main speakers at the 54th An-nual International Fire Instructors' Conference,Memphis, Tennessee, March 29, 1982.

In 1981 he received the nation's highest awardfor safety from the National Safety Council inChicago, "The Distinguished Service to SafetyAward".

DISCUSSION

QUESTION: When the tank cars of ammonia are over-turned, how do you remove the contents of a damagedvessel below 20% of its volume?

GREINER: This vapor absorption technique would stillbe effective as opposed to using a compressor or a pumpto remove ammonia from a damaged vessel down to the20% level. Depressurizing this way doesn't create anyadditional strain on the vessel.

QUESTION: Various studies show that denser-than-airsituations can exist when ammonia liquid becomes

airborne as is the case in some releases. Does thistechnique still work in these instances?

GREINER: I've done many releases, as I said earlier, withammonia liquid lines in all types of weather conditions,and I've experienced conditions where the ammoniavapor was, in fact, heavier than the air. However, this didnot seem to take away from the efficiency of water fogabsorption. Downwind control appeared effective withthe fog lines regardless of whether the ammonia vaporswere dense or buoyant.

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