msa gas detection handbook - heating and process...msa gas detection handbook 12 gas detection terms...

M S A G a s D e t e c t i o n H a n d b o o k

The MSA Gas Detection Handbook is designed to introduce users to key termsand concepts in gas detection and to serve as a quick reference manual forinformation such as specific gas properties, exposure limits and other data.

The Handbook contains:

• a glossary of essential gas detection terms and abbreviations.

• a summary of key principles in combustible and toxic gas monitoring.

• reference data—including physical properties and exposure limits—for the most commonly monitored gases, in industrial and variousother environments.

• a comparison of the most widely-used gas detection technologies.

• a table indicating the gas hazards common to specific applicationswithin major industries.

• a summary of key gas detection instrumentation approvalsinformation, including hazardous locations classification.

• MSA’s exclusive Sensor Placement Guide, detailing important factors to take into consideration when determining optimum gas sensor placement.

Note to User:

Mine Safety Appliances Company (“MSA”) makes no warranties,understandings or representations, whether expressed, implied or statutoryregarding this gas detection handbook. MSA specifically disclaims anywarranty for merchantability or fitness for a particular purpose. In no eventshall MSA, or anyone else who has been involved in the creation, productionor delivery of this handbook be liable for any direct, indirect, special,incidental or consequential damages arising out of the use of or inability touse this handbook or for any claim by any other party.


Table of Contents

Section 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Gas Detection Terms & Abbreviations

Section 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Gas Monitoring CategoriesCombustible AtmospheresToxic Atmospheres Oxygen Deficiency/ Enrichment AtmospheresGas Detection TechnologiesGas Sampling

Section 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49Gas Information Table

Section 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71A Selection of Gases Typically Associated with Various Industries

Section 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103ApprovalsHazardous Locations Classification

CLASS I: Flammable Gases, Vapors or Liquids

CLASS II: Combustible DustsCLASS III: Ignitable Fibers & Flyings

ATEX Explosive AtmospheresA Selection of Recognized Testing LaboratoriesSystem Installation

Section 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131Sensor Placement Guide

Section 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139Calibration

Section 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142Resources

Section 1Gas Detection Terms & Abbreviations


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Gas Detection Terms & Abbreviations

ACGIH - American Conference of Governmental Industrial Hygienists.

Alarm Set Point - The selected gas concentration level at which an alarm is activated.

Ambient air - Surrounding air to which the sensing element is normally exposedin its installed position.

Asphyxiant - A substance that impairs normal breathing by displacing oxygen.

Atmosphere - The total gases, vapors, mists and fumes present in a specific location.

Autoignition Temperature [also “spontaneous ignition temperature” (SIT) - Theminimum temperature at which a combustible substance (gas, vapor, liquid or solid) will ignite and sustain combustion under its own heat energy.

Bump Check (Functional Test) - Procedure used to verify the response of aninstrument which does not include actual adjustment. (also known as “Span Check”)

Calibration - Procedure by which the performance of a detector is verified tomaximize the accuracy of its readings. A calibration is performed by: (1)comparing the instrument with a known standard, and (2) adjusting theinstrument reading to match the standard.

Calibration Gas (also “Span Gas”) - A known concentration of gas that is usedto set instrument accuracy.

Ceiling - The maximum gas concentration to which a worker may be exposed.

Combustible Gas* - A gas that is capable of igniting and burning.

Combustion - The rapid oxidation of a substance involving heat and light.

Confined Space - An area that is large enough for an employee to bodily enterand perform work, has limited or restricted areas of entry or exit, and is notdesigned for continuous human occupancy.

* Any material that will burn at any temperature is considered to be“combustible”, so this term covers all such materials, regardless of how easilythey ignite. The term “flammable” specifically refers to those combustible gasesthat ignite easily and burn rapidly.


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Controller - The part of a gas detector that provides centralized processing ofthe gas signal. The controller receives and responds to the electrical signalfrom the sensor to output an indication, alarm or other function.

Cross Sensitivity - The predictable response of a detector to compounds otherthan the target gas.

Dew Point - The temperature at which a gas (air) is saturated with acondensable component.

Diffusion - Process by which particles spread from regions of higherconcentration to regions of lesser concentration as a result of randommolecular movement. Also used to describe the process by which theatmosphere being monitored is transported to the gas-sensing element bynatural random molecular movement.

Electrochemical Sensor - A sensor that uses an electrochemical reaction toprovide an electrical output proportional to the measured gas concentration.

Explosion - Rapid uncontrolled combustion process which generates a hightemperature, a large volume of gas, and a pressure or shock wave.

Explosionproof (XP) - Method of protection in which an explosion in a hazardous location is prevented by containing any combustion within thedevice, and thereby, preventing it from spreading into the atmospheresurrounding the enclosure.

Explosive (or “Flammable”) Limits - Though a flammable liquid can supportcombustion at its flash point temperature, to sustain it requires the vaporconcentration to be between two specific levels, or “flammable limits”, the lower flammable limit and the upper flammable limit. (see below) Any gas or vapor concentration that falls between these two limits is in theflammable range.

• Lower Explosive (or “Flammable”) Limit (LEL) - the minimumconcentration of a vapor (usually expressed as the percentage ofmaterial in air) required to sustain a fire.

• Upper Explosive (or “Flammable”) Limit (UEL) - the maximumconcentration of a vapor (usually expressed as the percentage ofmaterial in air) beyond which a fire cannot be sustained, as theamount of oxygen would be insufficient to continue the fire.


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Explosive (or “Flammable”) Range - The range that encompasses any gas orvapor concentration between the substance’s lower explosive limit and upperexplosive limit, and is therefore capable of sustaining combustion.

Flammable Gas* - This term applies to a special group of combustible gasesthat ignite easily and burn rapidly.

Flash Point - The minimum temperature at which a liquid gives off enough vaporto form an ignitable mixture with air (reaching 100% LEL).

Gas - A state of matter characterized by very low density and viscosity (relativeto liquids and solids), comparatively great expansion and contraction withchanges in pressure and temperature, ability to diffuse readily into other gases,and ability to occupy with almost complete uniformity the whole of anycontainer. (Often used interchangeably with “vapor”.)

Gas Detection Instrument - A device composed of electrical, optical,mechanical or chemical components that senses and responds to the presenceof gas mixtures.

General Purpose (GP) Enclosure - An enclosure intended for indoor use in non-hazardous rated areas, primarily to prevent accidental contact of personnelwith the enclosed equipment in areas where unusual service conditions do not exist.

Hazardous Atmosphere - (As defined by OSHA 29 CFR 1910.146) An atmospherein which workers are exposed to the risk of death, injury, incapacitation orillness.

Humidity - The amount of water vapor present in the atmosphere.

IDLH (Immediately Dangerous to Life and Health)**The maximum concentration level of a substance (gas) from which a workercould escape within 30 minutes without developing immediate, severe orirreversible health effects, or other escape-impairing symptoms. IDLH levels aremeasured in ppm (parts per million).**As defined by NIOSH (National Institute for Occupational Safety and Health).

* Any material that will burn at any temperature is considered to be“combustible”, so this term covers all such materials, regardless of how easily they ignite. The term “flammable” specifically refers to those combustiblegases that ignite easily and burn rapidly.


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Interferent - Any gas other than the target gas that will cause a response from agas sensor.

Intrinsic Safety (IS) - A method of protection in which an explosion is preventedthrough an electrical design using energy storage devices in which thepossibility of ignition is eliminated.

LEL (Lower Explosive Limit) - (see “Explosive Limits”)

Monitor - An instrument used to continuously measure a condition that must bekept within specific limits.

NIOSH - National Institute for Occupational Safety and Health.

OSHA - United States Department of Labor Occupational Safety and HealthAdministration.

Oxygen Deficient Atmosphere - An atmosphere containing less than 19.5%oxygen by volume. (Possesses a risk of insufficient oxygen for breathing.)

Oxygen Enriched Atmosphere - An atmosphere containing more than 20.8%oxygen by volume. (Possesses an increased risk of explosion.)

PEL (Permissible Exposure Limit) - An airborne concentration of contaminantthat most workers can be exposed to repeatedly in a normal 8- hour day, in a 40-hour week, without adverse health effects. PEL levels are measured in ppm(parts per million) and are established by OSHA.

Permanent (or Fixed) Gas Monitor - A gas monitor that is permanently installedin a location.

PPM (Parts Per Million) - The most common unit of measurement for toxicgases. A “10,000 parts per million” gas concentration level equals a 1% byvolume exposure.

Relative Density - The density of a gas as compared to that of another gas(typically air). In gas detection, relative density is used to assist in determiningoptimum sensor placement. If the relative density of the monitored gas is lessthan 1, then it will tend to rise in air; if the relative density is greater than 1 thenit will tend to sink in air and accumulate at ground level.


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Sensor - The part of a gas detector that converts the presence of a gas or vaporinto a measurable signal.

Smart Sensor - Sensor that contains a microprocessor, allowing it to recorddata, communicate with other devices or control devices such as relays.

Span Check - (see “Bump Check”).

STEL - Short-term exposure limit ( See “TLV - STEL”).

TLV® (Threshold Limit Value)* - Refers to the airborne concentration ofsubstances and represents conditions under which it is believed that nearly allworkers may be repeatedly exposed day after day without adverse healtheffects.* As defined by the ACGIH (American Conference of Governmental IndustrialHygienists).

There are three categories of TLVs:

TLV - TWA (Time Weighted Average) - This is the average amount ofgas that a worker can be repeatedly exposed to in a normal 8-hourday, in a 40-hour week, without adverse health effects.

TLV - STEL (Short Term Exposure Limit) -The gas concentration thatmost workers can be continuously exposed to for a 15-minute timeperiod without suffering adverse health affects that would impair self-rescue or worker safety. This limit should not be repeated more than 4 times per day and there should be at least 60 minutes betweenindividual STEL exposure periods.

TLV - C (Ceiling) - The highest gas concentration to which workersmay be exposed. Ceiling TLVs should never be exceeded and theytake precedence over all TWAs and STELs.

Toxic Atmosphere - An atmosphere in which the concentration of gases, dusts,vapors or mists exceeds the permissible exposure limit (PEL).

Toxic Gas or Vapor - Substance that causes illness or death when inhaled orabsorbed by the body in relatively small quantities.


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True Zero - A reading indicating that no amount of target gas is present in thesample. Also known as “baseline”.

TWA - Time-weighted average (see “TLV-TWA”).

UEL (Upper Explosive Limit) - (see “Explosive Limits”).

Vapor - Often used interchangeably with “gas”; vapor is generally used to referto the gaseous phase of a substance that generally exists as a liquid or solid atroom temperature, while “gas” is more commonly used to refer to a substancethat generally exists in the gaseous phase at room temperature.

Vapor Density - the weight of a volume of pure gas or vapor compared to that ofan equal volume of air at the same temperature and pressure. A vapor densityof less than 1 indicates that the gas or vapor is lighter than air and will tend torise. A vapor density of greater than 1 indicates that the vapor is heavier thanair and will tend to accumulate closer to the ground. It may also move asignificant distance at these low levels to a source of ignition and then flashback to the original location once ignited. When using vapor density todetermine optimum sensor placement, other factors such as air flow patternsand temperature gradients should also be considered.

Vapor Pressure - The pressure exerted when a solid or liquid is in equilibriumwith its own vapor. Vapor pressure is directly related to temperature. In gasdetection, this is significant because the higher the vapor pressure of asubstance, the greater the amount of it that will be present in vapor phase at agiven temperature, and thus a greater degree of gas hazard exists.

Zero Check - Check performed to verify that the instrument reads true zero.

Zero Gas - A cylinder of gas that is free of the gas of interest and interferents. It is used to properly zero an instrument’s base line.

Section 2Gas Monitoring CategoriesCombustible AtmospheresToxic AtmospheresOxygen Deficiency Enrichment AtmospheresGas Detection TechnologiesGas Sampling


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The Four Main Types of Gas HazardsThe following table summarizes the four main reasons why gas monitoring is performed:

Type of Monitoring The Purpose The Hazard

Possible Source of Hazard

Personalprotection

Worker safety Toxic gases Leaks, fugitiveemissions,industrial processdefects

Explosive Worker andfacility safety

Explosions Presence ofcombustiblegases/vapors dueto leaks, industrialprocess defects

Environmental Environmentalsafety

Environmentaldegradation

Oil leaks intosewers or lakes,Acid gasemissions

Industrial process Process control Malfunction of the process

Possible fault orother processerror


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Gas Monitoring CategoriesGas Monitoring Categories:

1. Combustible/ Flammable Gas• Explosive hazard.

• To avoid an explosion, atmospheric levels must be maintained belowthe lower explosive limit (LEL) for each gas, or purged of oxygen.

• Generally measured as 0-100% of the lower explosive limit or in partper million range.

• Combustible gas monitors are designed to alarm before a potentialexplosive condition occurs.

2. Toxic/ Irritant Gases• Hazardous to human health; worker exposure must be monitored.

• Typically measured in the part per million (ppm) range.

• Toxic gas monitors are designed to alert workers before the gas level reaches a harmful concentration.

• Some toxic gas monitors can calculate the average exposure overtime, providing short-term exposure limit (STEL) and time-weightedaverage (TWA) readings.

3. Oxygen• Atmospheres containing too little oxygen (less than 19.5% oxygen by

volume) are considered “oxygen deficient” and interfere with normalhuman respiration.

• Atmospheres containing too much oxygen (more than 25% oxygen byvolume) are considered “oxygen enriched” and possess an increasedrisk of explosion.

• Measured in the percent volume range (normal oxygen percentage inair is 20.8% by volume at sea level).

• Oxygen monitors are generally set to alarm if the atmosphere containseither too little or too much oxygen.


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Combustible AtmospheresCombustible AtmospheresIn order for a flame to exist, three conditions must be met. There must be:

• A source of fuel (e.g. methane or gasoline vapors).

• Enough oxygen (greater than 10-15%) to oxidize or burn the fuel.

• A source of heat (ignition) to start the process.

Examples of Heat and Ignition Sources

• Open flames such as those from lighters, burners, matches andwelding torches are the most common sources of ignition.

• Radiation in the form of sunlight or coming from hot surfaces.

• Sparks from various sources such as the switching on or off of electricappliances, removing plugs, static electricity or switching relays.


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Combustible AtmospheresCombustible Atmosphere FactorsVapor vs. GasThough often used interchangeably, the terms “vapor” and “gas” are notidentical. The term “vapor” is used to refer to a substance that, though presentin the gaseous phase, generally exists as a liquid or solid at room temperature.When we say that a liquid or solid substance is burning, it is actually its vaporsthat burn. “Gas” refers to a substance that generally exists in the gaseousphase at room temperature.

Vapor Pressure and Boiling PointVapor pressure is the pressure exerted when a solid or liquid is in equilibriumwith its own vapor. It is directly related to temperature. An example of vaporpressure is the pressure developed by the vapor of a liquid in a partially-filledclosed container. Depending on temperature, the vapor pressure will increaseup to a certain threshold. When this threshold is reached, the space isconsidered to be saturated.

The vapor pressure and boiling point of a chemical determine how much of it is likely to become airborne. Low vapor pressure means there are lessmolecules of the substance to ignite, so there is generally less of a hazardpresent. This also means that there are less molecules to sense, which maymake detection more challenging and require higher-sensitivity instrumentation.With higher vapor pressure and a lower boiling point, there is a greaterlikelihood of evaporation. If containers of chemicals with such properties areleft open, or if they’re allowed to spread over large surfaces, they are likely tocause greater hazards.

FlashpointA flammable material will not give off an amount of gas or vapor sufficient tostart a fire until it is heated to its flashpoint. Flashpoint is defined as the lowesttemperature at which a liquid produces sufficient vapor to produce a flame. Ifthe temperature is below this point, the liquid will not produce enough vapor toignite. If the flashpoint is reached and an external source of ignition such as aspark is provided, the material will catch fire. The National Fire ProtectionAgency’s NFPA’s document NFPA-325M, Fire Hazard Properties of FlammableLiquids, Gases and Volatile Solvents, lists the flashpoints of many commonsubstances. See www.nfpa.org.


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Combustible AtmospheresFlash points are significant because they give an indication of the degree ofhazard presented by a flammable liquid. Generally, the lower the flash point, theeasier it is for flammable fuel-air mixtures to form, and thus the greater hazard.

Autoignition TemperatureIf heated to a certain point—the spontaneous ignition (or “autoignition”)temperature—most flammable chemicals can spontaneously ignite under itsown heat energy, without an external source of ignition.


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Combustible AtmospheresVapor DensityVapor density is the weight ratio of a volume of flammable vapor compared toan equal volume of air. Most flammable vapors are heavier than air so theygravitate toward the ground, settling in low areas. A gas or vapor with a vapordensity greater than 1 may travel at low levels to find a source of ignition (e.g.hexane, which has a 3.0 vapor density); a gas or vapor with a vapor density lessthan 1 will tend to rise (e.g. methane, which has a 0.6 vapor density). Vapordensity is important to consider when determining optimum sensor placementbecause it helps predict where the gas or vapor is most likely to accumulate ina room or area.

Explosive LimitsTo produce a flame, a sufficient amount of gas or vapor must exist. But toomuch gas can displace the oxygen in an area and fail to support combustion.Because of this, there are limits at both low-end and high-end gas concen-trations where combustion can occur. These limits are known as the LowerExplosive Limit (LEL) and the Upper Explosive Limit (UEL). They are also referredto as the Lower Flammability Limit (LFL) and the Upper Flammability Limit (UFL).

To sustain combustion, the atmosphere must contain the correct mix of fuel andoxygen (air). The LEL indicates the lowest quantity of gas which must be presentfor combustion and the UEL indicates the maximum quantity of gas. The actualLEL level for different gases may vary widely and are measured as a percent byvolume in air. Gas LELs and UELs can be found in NFPA 325.

LELs are typically 1.4% to 5% by volume. As temperature increases, less energyis required to ignite a fire and the percent gas by volume required to reach 100%LEL decreases, increasing the hazard. An environment containing enrichedoxygen levels raises the UEL of a gas, as well as its rate and intensity ofpropagation. Since mixtures of multiple gases add complexity, their exact LELmust be determined by testing.

Most combustible gas instruments measure in the LEL range and display gasreadings as a percentage of the LEL. For example: a 50% LEL reading means thesampled gas mixture contains one-half of the amount of gas necessary tosupport combustion.


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Combustible Atmospheres

Any gas or vapor concentration that falls between these two limits is in theflammable (explosive) range. Different substances have different flammablerange widths — some are very wide and some are narrower. Those with awider range are generally more hazardous since a larger amount ofconcentration levels can be ignited.

Atmospheres in which the gas concentration level is below the LEL (insufficientfuel to ignite) are referred to as too “lean” to burn; those in which the gas levelis above the UEL (insufficient oxygen to ignite) are too “rich” to burn.

Gas Type 100% LEL UEL

Methane 5.0% gas by volume 15.0% gas by volume

Hydrogen 4.0% gas by volume 75.0% gas by volume

Propane 2.1% gas by volume 9.5% gas by volume

Acetylene 2.5% gas by volume 100% gas by volume


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Toxic AtmospheresToxic Gas MonitoringA toxic gas is one which is capable of causing damage to living tissue,impairment of the central nervous system, severe illness or—in extremecases—death, when ingested, inhaled or absorbed by the skin or eyes. Theamounts required to produce these results vary widely with the nature of thesubstance and exposure time. “Acute” toxicity refers to exposure of shortduration, such as a single brief exposure. “Chronic” toxicity refers to exposureof long duration, such as repeated or prolonged exposures.

Toxic gas monitoring is important because some substances can’t be seen orsmelled and have no immediate effects. Thus the recognition of a gas hazard viaa worker’s senses often comes too late, after concentrations have reachedharmful levels.

The toxic effects of gases range from generally harmless to highly toxic. Someare life-threatening at even short, low-level exposures, while others arehazardous only upon multiple exposures at higher concentrations. The degreeof hazard that a substance poses to a worker depends upon several factorswhich include the gas concentration level and the duration of exposure.

Exposure LimitsThe American Conference of Governmental Industrial Hygienists (ACGIH)publishes an annually revised list of recommended exposure limits for commonindustrial compounds, titled “TLV“s and BEI“s Based on the Documentation ofthe Threshold Limit Values for Chemical Substances and Physical Agents andBiological Exposure Indices”. (To order a copy, see www.acgih.org). ACGIHdeveloped the concept of Threshold Limit Value“ (TLV), which is defined as theairborne concentration of a contaminant to which it is believed that almost allworkers may be repeatedly exposed, day after day, over a working lifetimewithout developing adverse effects. These values are based on a combinationof industrial experience and human and animal research.

Time Weighted Averages (TWAs)TLVs are generally formulated as 8-hour time-weighted averages. Theaveraging aspect enables excursions above the prescribed limit as long as theyare offset by periods of exposure below the TLV.


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Toxic AtmospheresShort-Term Exposure Limits (STELs)Short-term exposure limits are concentrations above the 8-hour average towhich workers may be exposed for short periods of time without harmfuleffects. (If the concentration is high enough, even a one-time exposure canproduce harmful health effects.) STELs are used to govern situations in which aworker is exposed to a high gas concentration, but only for a short period oftime. They are defined as 15-minute time-weighted averages that are not to beexceeded even if the 8-hour TWA is below the TLV.

Ceiling ConcentrationsFor some toxic gases, a single exposure exceeding the TLV may be hazardousto worker health. In these cases, ceiling concentrations are used to indicatelevels that are never to be exceeded.

Permissible Exposure Limits (PELs)PELs are enforced by the Occupational Safety and Health Administration(OSHA). Part 29 of the Code of Federal Regulations (CFR) Section 1910.1000contains these standards, which are similar to ACGIH TLVs except that they arelegally enforceable rather than simply recommendations. However, the mostaccurate PELs are listed in the associated Material Safety Data Sheets (MSDS).

Immediately Dangerous to Life and Health (IDLH)The National Institute for Occupational Safety and Health (NIOSH) defines anIDLH exposure condition atmosphere as one that poses a threat of exposure toairborne contaminants when that exposure is likely to cause death or immediateor delayed permanent adverse health effects or prevent escape from such anenvironment. Since IDLH values exist to ensure that a worker can escape froma hazardous environment in the event of failure of respiratory protectionequipment, they are primarily used to determine appropriate respiratoryselection in compliance with OSHA standards.


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Toxic AtmospheresWeb resources:

ACGIH: http://www.acgih.org/TLV

OSHA: http://www.osha.gov

NIOSH: http://www.cdc.gov/niosh/homepage.html

Gas detection systems are used to monitor toxic gases in primarily two types ofmonitoring applications:

1. Ambient air monitoring (includes leak monitoring)

• low-level gas detection for worker safety

• to reduce leakage of expensive compounds (e.g., refrigerants)

2. Process monitoring

• to monitor levels of compounds used in chemical synthesis processes (e.g., in the plastics, rubber, leather and food industries)

• from low ppm levels to high % by volume levels

For toxic gas monitoring, electrochemical, metal oxide semiconductor (solidstate), infrared and photoionization are the sensing technologies mostcommonly used.


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Oxygen Deficiency/EnrichmentOxygen DeficiencyNormal ambient air contains an oxygen concentration of 20.8% by volume.When the oxygen level dips below 19.5% of the total atmosphere, the area isconsidered oxygen deficient. In oxygen-deficient atmospheres, life-supportingoxygen may be displaced by other gases, such as carbon dioxide. This results inan atmosphere that can be dangerous or fatal when inhaled. Oxygen deficiencymay also be caused by rust, corrosion, fermentation or other forms of oxidationthat consume oxygen. As materials decompose, oxygen is drawn from theatmosphere to fuel the oxidation process.

The impact of oxygen deficiency can be gradual or sudden, depending on theoverall oxygen concentration and the concentration levels of other gases in theatmosphere. Typically, decreasing levels of atmospheric oxygen cause thefollowing physiological symptoms:

Oxygen EnrichmentWhen the oxygen concentration rises above 20.8% by volume, the atmosphereis considered oxygen-enriched and is prone to becoming unstable. As a resultof the higher oxygen level, the likelihood and severity of a flash fire or explosionis significantly increased.

% Oxygen Physiological Effect

19.5 - 16 No visible effect.

16 - 12 Increased breathing rate. Accelerated heartbeat.Impaired attention, thinking and coordination.

14 – 10Faulty judgment and poor muscular coordination.Muscular exertion causing rapid fatigue.Intermittent respiration.

10 – 6Nausea and vomiting. Inability to perform vigorousmovement, or loss of the ability to move.Unconsciousness, followed by death.

Below 6 Difficulty breathing. Convulsive movements. Death in minutes.


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Gas Detection TechnologiesGas Detection Technologies There are a variety of gas detection technologies in use today. Among the mostcommonly employed are:

• Catalytic Bead

• Metal Oxide Semiconductor (also known as “solid state”)

• Point Infrared Short Path

• Open (Long Path) Infrared

• Photoacoustic Infrared

• Electrochemical for Toxic Gas Detection

• Electrochemical for Oxygen Detection

• Thermal Conductivity

• Photoionization

• NDIR

The tables and diagrams on the following pages summarize the operation of each technology.


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Gas Detection Technologies

Technology Catalytic bead

Gas TypeDetected Combustible gas

Principle ofOperation

Uses a catalytic bead to oxidize combustible gas; aWheatstone Bridge converts the resulting change inresistance into a corresponding sensor signal.

Description -Detailed

A wire coil is coated with a catalyst-coated glass or ceramicmaterial, and is electrically heated to a temperature thatallows it to burn (catalyze) the gas being monitored,releasing heat and increasing the temperature of the wire.As the temperature of the wire increases, so does itselectrical resistance. This resistance is measured by aWheatstone Bridge circuit and the resulting measurement isconverted to an electrical signal used by gas detectors. Asecond sensor, the compensator, is used to compensate fortemperature, pressure and humidity.

Readings % LEL

ProsLong life, less sensitive to temperature, humidity, condensationand pressure changes; high accuracy; fast response; monitorsa wide range of combustible gases and vapors in air.

Cons Subject to sensor poisoning; requires air or oxygen; shortenedlife with frequent or continuous exposure to high LELs.


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Typical Catalytic Bead Sensor Operation


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Technology Metal Oxide Semiconductor

Gas TypeDetected Combustible gas; Toxic gas


Made of a metal oxide that changes resistance in response to the presence of a gas; this change is measured andtranslated into a concentration reading.


A semiconducting material (metal oxide) is applied to a non-conducting substance (substrate) between two electrodes.The substrate is heated to a temperature at which thepresence of the gas can cause a reversible change in theconductivity of the semi-conducting material. When no gas ispresent, oxygen is ionized onto the surface and the sensorbecomes semi-conductive; when molecules of the gas ofinterest are present, they replace the oxygen ions,decreasing the resistance between the electrodes. Thischange is measured electrically and is proportional to theconcentration of the gas being measured.

Readings PPM

Pros High sensitivity (detects low concentrations); wide operatingtemperature range; long life.

Cons Non-specific (cross-sensitive to other compounds); nonlinearoutput; sensitive to changes in humidity: subject to poisoning.


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Typical Metal Oxide Semiconductor (Solid State) Sensor Operation

Silicon Chip

Sensor Film

Heater


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Technology Point Infrared Short Path



[Also referred to as Non-Dispersive Infrared (NDIR)];Absorptive IR uses a gas ability to absorb IR radiation. Two gas samples--the gas of interest, and an inert referencegas--are exposed to infrared light. The amount of lighttransmitted through each sample is compared to determinethe concentration of the gas of interest.


Uses an electrically modulated source of infrared energy andtwo detectors that convert the infrared energy into electricalsignals. Each detector is sensitive to a different range ofwavelengths in the infrared portion of the spectrum. Thesource emission is directed through a window in the mainenclosure into an open volume. A mirror may be used at theend of this volume to direct the energy back through thewindow and onto the detectors.

The presence of a combustible gas will reduce the intensityof the source emission reaching the analytical detector, butnot the intensity of emission reaching the reference detector.The microprocessor monitors the ratio of these two signalsand correlates this to a %LEL reading.

Readings % LEL

Pros

High accuracy and selectivity; large measurement range; low maintenance; highly resistant to chemical poisons; doesnot require oxygen or air; span drift potential virtuallyeliminated (no routine calibration required); fail-to-safe.

Compared to open-path IR, provides exact gas level (but at point of detection only).

Cons Not suitable for hydrogen detection.


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Typical Point Infrared Short Path Operation


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Technology Open Path Infrared



Operates similarly to point infrared detectors, except that theIR source is separated from the detector.


Open-path IR monitors expand the concepts of point IRdetection to a gas sampling path of up to 100 meters. Likepoint IR monitors, they utilize a dual beam concept. The"sample" beam is in the infrared wavelength which absorbshydrocarbons, while the second "reference" beam is outsidethis gas absorbing wavelength. The ratio of the two beams iscontinuously compared. When no gas is present, the signalratio is constant; when a gas cloud crosses the beam, thesample signal is absorbed or reduced in proportion to theamount of gas present while the reference beam is not.System calculates the product of the average gasconcentration and the gas cloud width, and readings aregiven in %LEL/meter.

Readings % LEL per meter

Pros

High accuracy and selectivity; large measurement range; low maintenance; highly resistant to chemical poisons; doesnot require oxygen or air; span drift potential virtuallyeliminated (no routine calibration required); fail-to-safe.

Cons

Not suitable for hydrogen detection.

Compared with point IR detection, is not capable of isolating the leak source.

Requires unobstructed path between source and detector.


35

Gas Detection TechnologiesTypical Open Long Path Infrared Operation


36


Technology Photoacoustic Infrared

Gas TypeDetected Combustible gas; Toxic gas


Uses a gases ability to absorb IR radiation and the resulting change in pressure.


The gas sample is exposed to infrared light; as it absorbslight its molecules generate a pressure pulse. The magnitudeof the pressure pulse indicates the gas concentrationpresent.

Readings % LEL, % by volume, PPM, PPB

Pros High sensitivity; linear output; easy to handle; not subject to poisoning; long-term stability.

Cons Not suitable for hydrogen detection.


37

Gas Detection TechnologiesPumped Photoacoustic Infrared Operation

(Diffusion method also available)

Sample gas enters the measuring cell.

The gas is irradiated with pulsed infrared energy.


38


The gas molecules heat and cool as they absorb the infrared energy. The pressurechanges as a result of the heating and cooling of the molecules measured by thedetector. This pressure change is converted into a gas reading.

The gas is exhausted and a fresh sample enters the cell. This sampling processis continuously repeated.


39


Technology Electrochemical Toxic Gases

Gas TypeDetected Toxic gas


Uses an electrochemical reaction to generate a currentproportional to the gas concentration.


Sensor is a chamber containing a gel or electrolyte and two active electrodes--the measuring (sensing/working)electrode (anode) and the counter electrode (cathode). A third electrode (reference) is used to build up a constantvoltage between the anode and the cathode. The gas sampleenters the casing through a membrane; oxidation occurs atthe anode and reduction takes place at the cathode. Whenthe positive ions flow to the cathode and the negative ionsflow to the anode, a current proportional to the gasconcentration is generated.

Readings PPM readings for toxic gases

Pros High sensitivity; linear output; easy to handle.

Cons Limited shelf life; subject to interferents; sensor lifetimeshortened in very dry and very hot environments.


40


Typical Electrochemical Toxic Sensor


41


Technology Electrochemical Oxygen

Gas TypeDetected Oxygen deficiency/ enrichment


Uses an electrochemical reaction to generate a currentproportional to the gas concentration.


Sensor is a chamber containing a gel or electrolyte and twoelectrodes--the measuring (sensing/working) electrode andthe (usually lead) counter/reference electrode. The gassample enters the casing through a membrane; oxidationoccurs at the anode and reduction takes place at thecathode. When the positive ions flow to the cathode and thenegative ions flow to the anode, a current proportional to thegas concentration is generated.

Readings Percent volume readings for oxygen

Pros High sensitivity; linear output; easy to handle; not subject to poisoning.

ConsLimited shelf life; subject to interferents; sensor life shortened in very dry and very hot environments, or inenriched O2 applications.


42


Typical Electrochemical Oxygen Sensor


43


Technology Thermal Conductivity

Gas TypeDetected Combustible gas; Toxic gases


Measures the gas sample's ability to transmit heat bycomparing it with a reference gas (usually air).


Two sensors (detecting sensor and compensating sensor)are built into a Wheatstone Bridge. The detecting sensor isexposed to the gas of interest; the compensating sensor isenclosed in a sealed compartment filled with clean air.Exposure to the gas sample causes the detecting sensor tocool, changing the electrical resistance. This change isproportional to the gas concentration. The compensatingsensor is used to verify that the temperature change iscaused by the gas of interest and not by ambienttemperature or other factors.

Readings PPM; up to 100% by volume

Pros Wide measuring range.

Cons

Non-specific (cross-sensitive to other compounds); does not work with gases with thermal conductivities (TCs)close to one (that of air, NH3, CO, NO, O2, N2); gases with TCs of less than one are more difficult to measure; outputsignal not always linear.


44


Typical Thermal Conductivity Sensor


45


Technology Photoionization

Gas TypeDetected Toxic (organic compounds)

Principle ofOperation Uses ionization as the basis of detection.


A photoionization detector (PID) uses an ultraviolet lamp to ionize the compound of interest. Ions are collected on a‘getter’, a current is produced and the concentration of the compound is displayed in parts per million on theinstrument meter.

Readings PPM, sub-ppm

Pros Fast response speed, very low level detection, detects a large number of substances.

Cons More expensive, increased maintenance, requires morefrequent calibration, non-specific, sensitive to humidity.


46


Typical Photoionization Sensor Design


47

Gas SamplingGas SamplingThere are three methods of gas sampling:

• Diffusion Sampling

• Pumped Sampling

• Aspirated Sampling

Diffusion SamplingDiffusion is the natural movement of molecules away from an area of highconcentration to an area of lower concentration. The term “diffusion” denotesthe process by which molecules or other particles intermingle as a result oftheir random thermal motion. Ambient conditions such as temperature, aircurrents and other characteristics affect diffusion.

Advantages:• Most effective placement is at desired sampling point.

• Fast response because no sample transport is required.

• No pumps and/or filters to maintain.

Pumped SamplingPumped sampling uses a pump to pull the sample from a remote location into or through the sensor. With pumped sampling, samples can be gatheredsimultaneously from two or more locations.


48

Gas SamplingConditions Favoring Pumped Sampling:

• Sampling point is too hot/cold.

• Sampling point is difficult to access.

• Heavy vapor present that does not diffuse well by natural forces.

• An application can be converted from an explosionproof (XP) rating toa general purpose (GP) rating through pumped operation. (Flashbackarrestors may be necessary between the sample port and the sensor.)

• Confined Spaces

Aspirated SamplingAspirated sampling uses suction to draw the sample from a remote location intoor through the sensor.

Advantages of Aspirated Sampling Versus Pumped:

• Lower cost

• Reduced maintenance because there are no moving parts

Section 3Gas Information Table


50

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Acet

alde

hyde

Acet

ic a

ldeh

yde

C 2H 4

OHe

avie

rX

-38

4.0

60-

25 [C

]20

02,

000

XX

X17

521

750

Acet

ic A

cid

C 2H 4

O 2He

avie

rX

394.

019

.910

1510

50X

XX

X46

311

811

Acet

ical

dehy

deAc

etal

dehy

deC 2

H 4O

Heav

ier

X-3

84.

060

-25

[C]

200

2,00

0X

XX

175

2175

0

Acet

one

C 3H 6

OHe

avie

rX

-20

2.5

12.8

500

750

1,00

02,

500

XX

XX

465

56

Acet

onitr

ileC 2

H 3N

Heav

ier

X6

3.0

1620

-40

500

XX

XX

524

8273

Acet

ylen

eC 2

H 2Li

ghte

rX

Gas

2.5

100

AA

--

XX

XX

305

-83

Acro

leic

aci

dAc

rylic

aci

dC 3

H 4O 2

Heav

ier

X50

2.0

82

--

-X

XX

438

142

3

Acro

lein

Acry

lald

ehyd

eC 3

H 4O

Heav

ier

X-2

62.

831

-0.

1 [C

]0.

12

XX

XX

220

5221

0

Acry

lald

ehyd

eAc

role

inC 3

H 4O

Heav

ier

X-2

62.

831

-0.

1 [C

]0.

12

XX

XX

220

5221

0

Acry

lic a

cid

Acro

leic

aci

dC 3

H 4O 2

Heav

ier

X50

2.0

82

--

-X

XX

438

142

3

Acry

loni

trile

C 2H 3

NHe

avie

rX

03.

017

2-

285

XX

X48

177

83

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor

Thermal Conductivity

Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


51

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Ally

l alc

ohol

2-pr

open

ylC 3

H 6O

Heav

ier

X21

2.5

180.

5-

220

XX

XX

378

9717

Ally

l Chl

orid

eC 3

H 5Cl

Heav

ier

X-3

22.

911

.11

21

250

XX

392

4529

5

Amm

onia

NH 3

Ligh

ter

XGa

s15

.028

2535

5030

0X

XX

X65

1-3

340

0 @

45°

C

Amyl

ace

tate

, n-

C 7H 1

4O2

Heav

ier

X16

1.1

7.5

--

100

1,00

0X

XX

360

149

Arsi

neAs

H 3He

avie

rX

Gas

5.1

780.

05-

0.05

3X

-62

>760

Benz

eneˆ

C 6H 6

Heav

ier

X-1

11.

37.

10.

52.

510

500

XX

XX

498

8075

Benz

ene

chlo

ride

Chlo

robe

nzen

eC 6

H 5Cl

Heav

ier

X29

1.3

9.6

10-

751,

000

XX

XX

638

132

12

Brom

ine

Br2

Heav

ier

n/a

n/a

n/a

0.1

0.2

0.1

3X

5917

5

Brom

ochl

orod

iflu

orom

etha

neHa

lon

1211

CF2C

lBr

Heav

ier

n/a

n/a

n/a

--

--

XX

X-

3.3

778

Brom

omet

hane

Met

hylb

rom

ide

CH3B

rHe

avie

rX

n/a

10.0

161

-20

[C]

250

[Ca]

XX

XX

537

41,

250

Brom

otrifl

uoro

met

hane

Halo

n 13

01CB

rF3

Heav

ier

n/a

n/a

n/a

1,00

0-

1,00

0-

XX

X-

-58

12,1

53 @

25°C

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


52

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Buta

dien

esC 4

H 10

Heav

ier

X-7

62.

011

.52

(-)1

2,00

0X

XX

X42

0-4

Gas

Buta

ne, n

-C 4

H 10

Heav

ier

XGa

s1.

58.

580

0-

--

XX

XX

287

-1

Buta

nol,

n-Bu

tyl a

lcoh

olC 4

H 10O

Heav

ier

X29

1.4

11.2

20-

100

1,40

0X

XX

X34

311

7

Buta

nol,

sec-

Buty

l alc

ohol

C 4H 1

0OHe

avie

rX

241.

79.

810

0-

150

2,00

0X

XX

X40

594

Buta

none

, 2-

Met

hyle

thyl

keto

neC 4

H 8O

Heav

ier

X-9

1.4

11.4

200

300

200

3,00

0X

XX

X40

480

Buty

l ace

tate

, n-

C 6H 1

2O2

Heav

ier

X22

1.3

7.6

150

200

150

1,70

0X

XX

X42

012

7

Buty

l ace

tate

, sec

-C 6

H 12O

2He

avie

rX

171.

79.

820

0-

200

1,70

0X

XX

X-

112

Buty

l ace

tate

, ter

tC 6

H 12O

2He

avie

rX

221.

5-

200

-20

01,

500

XX

XX

-

Buty

l acr

ylat

e, n

-C 6

H 12O

2He

avie

rX

291.

59.

92

--

-X

XX

X26

712

7

Buty

l alc

ohol

, n-

Buta

nol,

n-C 4

H 10

Heav

ier

X29

1.4

11.2

20-

100

1,40

0X

XX

X34

311

7

Buty

l eth

ylen

ehe

xyle

neHe

xene

, 1-

C 6H 1

2He

avie

rX

-26

1.2

6.9

50-

--

XX

X25

363

308

@ 3

8°C

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


53

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Buty

rald

ehyd

eBu

tyla

ldeh

yde:

buta

nal

C 4H 8

OHe

avie

rX

-22

1.9

12.5

--

--

XX

XX

218

76

Carb

on d

ioxi

deCO

2He

avie

rn/

an/

an/

a5,

000

30,0

005,

000

40,0

00X

XX

-

Carb

on d

isul

fide

CS2

Heav

ier

X-3

01.

350

10-

2050

0X

9046

300

Carb

on m

onox

ide

COSl

ight

ly li

ghte

rX

Gas

12.0

7525

-50

1,20

0X

XX

XX

609

-192

>760

Carb

on te

trach

lorid

eTe

trach

loro

met

hane

CCl 4

Heav

ier

n/a

n/a

n/a

510

1020

0X

X-

7791

Carb

onyl

chl

orid

ePh

osge

neCO

Cl2

Heav

ier

n/a

n/a

n/a

0.1

-0

2X

X-

856

8 @

0°C

Chlo

rine

Cl2

Heav

ier

Gas

-n/

a0.

51

1 [C

]10

X-

-34

Gas

Chlo

rine

diox

ide

ClO 2

Heav

ier

n/a

n/a

n/a

0.1

0.3

0.1

5X

-

Chlo

robe

nzen

eBe

nzen

e ch

lorid

eC 6

H 5Cl

Heav

ier

X29

1.3

9.6

10-

751,

000

XX

X63

813

212

Chlo

roet

hane

Ethy

l chl

orid

eC 2

H 5Cl

Heav

ier

X-5

03.

815

.410

0-

1,00

03,

800

XX

X51

912

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


54

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Chlo

rofo

rmTr

ichl

orom

etha

neCH

Cl3

Heav

ier

n/a

n/a

n/a

10-

50 [C

]50

0X

X-

6216

0

Chlo

rom

etha

neM

ethy

l chl

orid

eCH

3Cl

Heav

ier

XGa

s-5

017

.450

100

100

2,00

0X

XX

632

-24

Cum

ene

Isop

ropy

lenz

ene

C 9H 1

2He

avie

rX

330.

96.

550

-50

500

XX

XX

425

152

3.2

Cycl

ohex

ane

C 6H 1

2He

avie

rX

-20

1.3

810

0-

300

1,30

0X

XX

X24

582

Cycl

ohex

anon

eC 6

H 10O

Heav

ier

X43

1.1

9.4

25-

5070

0X

XX

X42

015

6

Cycl

opet

ane

C 5H 1

0He

avie

rX

-37

1.1

8.7

600

--

-X

XX

X36

149

Diac

eton

e al

coho

lDi

acet

one

C 6H 1

2O2

Heav

ier

X58

1.8

6.9

50-

501,

800

XX

XX

603

164

Dibo

rane

Boro

etha

neB 2

H 6Sl

ight

ly h

eavi

erX

-90

0.8

980.

1-

0.1

15X

38-5

2-9

322

4 @

112

°C

Dich

loro

benz

ene,

o-

C 6H 4

Cl2

Heav

ier

X66

2.2

9.2

2550

50 [C

]20

0X

XX

X64

818

01.

2

Dich

loro

etha

ne .

1,1-

Ethy

liden

e di

chlo

ride

C 2H 4

Cl2

Heav

ier

X-1

75.

411

.410

0-

100

3,00

0X

XX

X45

857

-59

Dich

loro

etha

ne .1

,2-

Ethy

len

dich

lorid

eC 2

H 4Cl

2He

avie

rX

136.

215

.910

-50

50 [C

]X

XX

X41

384

100

@ 2

9°C

Diet

hyl e

ther

Ethy

l eth

erC 4

H 10O

Heav

ier

X-4

51.

936

400

500

400

1,90

0X

XX

X16

035

442

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


55

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Diet

hyl k

eton

eDE

KC 5

H 10O

Heav

ier

X12

1.6

6.4

200

300

--

XX

XX

450

103

Diet

hyla

min

eDi

etha

min

eC 4

H 11N

Heav

ier

X-2

81.

810

.15

1525

200

XX

XX

312

5619

4

Diet

hylb

enze

neDo

wth

erm

JC 1

0H14

Heav

ier

X55

--

--

--

XX

380

181

0.75

Diis

opro

pyla

min

eC 6

H 15N

Heav

ier

X-6

0.8

7.1

5-

520

0X

XX

X31

684

60

Diflu

orom

etha

neHF

C-32

CH2F

2He

avie

rX

n/a

12.7

33.4

--

--

XX

X64

7-5

211

,377

@

21°

C

Dim

ethy

l ace

tam

ide

C 4H 9

NO

Heav

ier

X70

1.8

11.5

10-

1030

0X

XX

X49

016

5

Dim

ethy

l eth

erDM

EC 2

H 6O

Heav

ier

XGa

s3.

427

--

--

XX

XX

350

-24

1, 4

Dim

ethy

lam

ine

DMA

C 2H 7

NHe

avie

rX

Gas

2.8

14.4

515

1050

0X

XX

X43

07

1500

@25

°C

Dim

ethy

leth

ylam

ine

C 2H 1

1NHe

avie

rX

-45

0.9

11.2

--

--

XX

X19

036

-

Dim

ethy

lform

amid

eDM

FC 3

H 7N

OHe

avie

rX

572.

215

.210

-10

500

XX

X44

515

3

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


56

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Dim

ethy

lsul

foxi

deC 2

H 6SO

942.

642

--

--

XX

X21

518

9

Diox

ane

Diet

hyle

ne d

ioxi

deC 4

H 8O 2

Heav

ier

X12

2.0

22-

-10

050

0X

XX

X18

010

129

Dow

ther

m J

Diet

hylb

enze

neC 1

0H14

Heav

ier

X55

--

--

--

XX

380

181

0.75

Epic

hlor

ohyd

rinC 3

H 5OC

lHe

avie

rX

313.

821

0.5

-5

75X

XX

X41

111

613

Etha

neC 2

H 6Sl

ight

ly h

eavi

erX

Gas

3.0

12.5

(15.

5)A

A-

AX

XX

X47

2-8

9

Ethe

neEt

hyle

neC 2

H 4Sl

ight

ly li

ghte

rX

Gas

2.7

3.6

AA

--

XX

XX

490

-104

Etho

xyet

hano

l, 2-

Cello

solv

eC 4

H 10O

2He

avie

rX

431.

715

.65

-20

050

0X

XX

X23

513

5

Ethy

l ace

tate

C 4H 8

O 2He

avie

rX

-42.

011

.540

0-

400

2,00

0X

XX

X42

777

Ethy

l acr

ylat

eC 5

H 8O 2

Heav

ier

X9

1.4

145

1525

300

[Ca]

XX

XX

372

100

31

Ethy

l alc

ohol

Etha

nol

C 2H 6

OHe

avie

rX

123.

319

1,00

0-

1,00

03,

300

XX

XX

363

78

Ethy

lben

zene

C 8H 1

0He

avie

rX

211.

06.

710

012

510

080

0X

XX

X43

213

67

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


57

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Ethy

l chl

orid

eCh

loro

etha

neC 2

H 5Cl

Heav

ier

X-5

03.

815

.410

0-

1,00

03,

800

XX

XX

519

12

Ethy

l eth

erDi

ethy

l eth

erC 4

H 10O

Heav

ier

X-4

51.

936

400

500

400

1,90

0X

XX

X16

035

442

Ethy

lene

Ethe

neC 2

H 4Sl

ight

ly li

ghte

rX

Gas

2.7

3.6

AA

--

XX

XX

490

-104

Ethy

lene

dich

lorid

e1,

2di

chlo

roet

hyle

neC 2

H 4Cl

2He

avie

rX

136.

215

.910

-50

50 [C

a]X

XX

X41

384

100

@29

°C

Ethy

lene

gly

col

C 2H 6

O 2He

avie

rX

111

3.2

15.3

-10

0m

g/m

3-

-X

398

197

Ethy

lene

oxi

deEt

OC 2

H 4O

Heav

ier

X-2

03.

010

01

-1

800

[Ca]

XX

XX

429

111,

095

Ethy

liden

edi

chlo

ride

Dich

loro

etha

ne,

1, 1

-C 2

H 3Cl

2He

avie

rX

-17

5.4

11.4

100

-10

03,

000

XX

XX

458

57-5

9

Fluo

rine

F 2He

avie

rn/

an/

an/

a1

20.

125

XX

X42

9-1

88

Furfu

ral

Furfu

rol

C 5H 4

O 2He

avie

rX

602.

119

.32

-5

100

XX

X31

616

22

Gaso

line

Hept

ane,

Hex

ane

-X

-42

1.4

7.6

300

500

-[C

a]X

XX

X

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


58

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Halo

n 12

11Br

omoc

hlor

odi-

fluor

omet

hane

CF2C

lBr

Heav

ier

n/a

n/a

n/a

--

--

XX

X-3

.377

8

Halo

n 13

01Br

omot

rifluo

ro-

met

hane

CBrF

3He

avie

rn/

an/

an/

a1,

000

-1,

000

-X

XX

-58

12,1

53 @

25°C

Hept

ane,

n-

C 7H 1

6He

avie

rX

-41.

16.

740

050

050

075

0X

XX

X20

498

1,29

3

Hexa

fluor

o 1,

3bu

tadi

ene

C 4F 6

Heav

ier

X-

773

--

--

XX

X-

64,

800

Hexa

fluor

opro

pene

Hexa

fluor

o-pr

opyl

ene

C 3F 6

Heav

ier

n/a

n/a

n/a

--

--

XX

X-

-30

4,80

0

Hesa

fluor

opro

pyle

neHe

xaflu

oro-

prop

ene

C 3F 6

Heav

ier

n/a

n/a

n/a

--

--

XX

X-

-30

Hexa

none

, 2-

Met

hyl b

utyl

keto

neC 6

H 12O

Heav

ier

X25

1.2

85

1010

01,

600

XX

X42

312

8

Hexe

ne, 1

-Bu

tyl e

thyl

ene

hexy

lene

C 6H 1

2He

avie

rX

-26

1.2

6.9

50-

--

XX

X25

363

308

@38

°C

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


59

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Hexa

ne, 2

-C 6

H 12

Heav

ier

X


60

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Hydr

ogen

chl

orid

eHy

droc

hlor

ic a

cid

HCl

Heav

ier

n/a

n/a

n/a

-5

[C]

5 [C

]50

X-

-85

Gas

Hydr

ogen

cya

nide

HCN

Ligh

ter

X-1

85.

640

-4.

7 [C

]10

50X

X54

026

Hydr

ogen

fluo

ride

HFLi

ghte

rn/

an/

an/

a-

3 [C

]3

30-

2076

0

Hydr

ogen

sul

fide

H 2S

Heav

ier

XGa

s4.

346

1015

20 [C

]10

0X

X26

0-6

014

,060

Isoa

myl

alc

ohol

C 5H 1

2OHe

avie

rX

431.

29

50-

100

500

XX

350

132

Isob

utan

eC 4

H 10

Heav

ier

XGa

s1.

88.

4-

--

-X

XX

X46

0-1

2

Isob

utyl

ace

tate

C 6H 1

2O2

Heav

ier

171.

310

.515

0-

150

1,30

0X

XX

X42

111

8

Isop

ar G

Isop

araf

finic

hydr

ocar

bon

Heav

ier

X38

1.2

9.6

XX

X>1

602.

3

Isop

horo

neC 9

H 14O

Heav

ier

X84

0.8

3.8

-5

[C]

2520

0X

XX

X46

021

5


61

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Isop

ropa

nol

Isor

opyl

alc

ohol

C 3H 8

OHe

avie

rX

112.

012

.740

050

040

02,

000

XX

XX

399

83

Isop

ropy

l ace

tate

C 5H 1

0O2

Heav

ier

X2

1.8

825

031

025

01,

800

XX

XX

460

90

Isop

rory

l alc

ohol

Isop

ropa

nol

C 3H 8

OHe

avie

rX

112.

012

.740

050

040

02,

000

XX

XX

399

83

Isop

ropy

lbe

nzen

eCu

men

eC 9

H 12

Heav

ier

X33

0.9

6.5

50-

5090

0X

XX

X42

515

23.

2

Isop

ropy

l eth

erDi

isop

ropy

l eth

erC 6

H 14O

Heav

ier

X-2

81.

47.

925

031

050

01,

400

XX

XX

443

69

Kero

sene

/JP-

1Je

t fue

lFu

el o

il no

. 1He

avie

rX

37-7

20.

75

--

--

XX

X21

015

1-30

1

Met

hane

CH4

Ligh

ter

XGa

s5.

015

AA

-A

XX

XX

X53

7-1

62

Met

hano

lM

ethy

l alc

ohol

CH4O

Heav

ier

X11

6.0

3620

025

020

06,

000

XX

X46

464

Met

hoxy

etha

nol,

2-M

ethy

l cel

loso

lve

C 3H 8

O 2He

avie

rX

391.

814

5-

2520

0X

XX

285

124

Met

hyl a

ceta

teC 3

H 6O 2

Heav

ier

X-1

03.

116

200

250

200

3,10

0X

XX

X45

460

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


62

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Met

hyl a

lcoh

olM

etha

nol

CH4O

Heav

ier

X11

6.0

3620

025

020

06,

000

XX

XX

464

64

Met

hyl b

rom

ide

Brom

omet

hane

CH3B

rHe

avie

rX

n/a

10.0

161

-20

[C]

250

[Ca]

XX

XX

537

4

Met

hyl b

utyl

keto

neHe

xano

ne, 2

-C 6

H 12O

Heav

ier

X25

1.2

85

1010

01,

600

X42

312

8

Met

hyl c

ello

solv

e2- m

etho

xyet

hano

lC 3

H 8O 2

Heav

ier

X39

1.8

145

-25

200

XX

X28

512

4

Met

hyl c

hlor

ide

Chlo

rom

etha

neCH

3Cl

Heav

ier

X-5

08.

117

.450

100

100

2,00

0X

XX

X63

2-2

4

Met

hylc

hlor

ofor

mTr

ichl

oroe

than

e,1,

1,1-

C 2H 3

Cl3

Heav

ier

X7

16.0

350

450

350

700

XX

XX

500

74

Met

hyl e

thyl

keto

ne (M

EK)

Buta

none

, 2C 4

H 8O

Heav

ier

X-9

1.4

11.4

200

300

200

3,00

0X

XX

X40

480

Met

hyl fl

uorid

eCH

3FHe

avie

rX

XX

X-7

828

,577

@21

.1°C

Met

hylfo

rmat

eC 2

H 4O 2

Heav

ier

X-1

95.

023

100

150

100

4,50

0X

XX

X45

632

476

Electrochemical

Catalytic

Photoacoustic IR

Absorptive IR

Semiconductor


Combustible

Dete

ctio

n Te

chno

logi

es

Gas

Info

rmat

ion

Tabl

e

Key:

[C] =

Cei

ling

Lim

it (n

ever

exc

eed)

A=

Asph

yxia

ntCa

= Ca

rcin

ogen

-= D

ata

not c

urre

ntly

ava

ilabl

en/

a=

Data

not

app

licab

le


63

Gas

or V

apor

Syno

nym

Chem

ical

Form

ula

Rela

tive

Dens

ity(v

s.Ai

r)+

Flas

hPo

int

(°C)

1 *

LEL

(% b

yvo

l)1

UEL

(% b

yvo

l)1

ACGI

HTLV

-TW

A(P

PM)2

ACGI

HTLV

-STE

L(P

PM)2

OSHA

PEL

(PPM

)3

NIO

SHID

LH(P

PM)4

Auto

-ig

nitio

nTe

mp

(°C)

*

Boil-

ing

Poin

t(°

C)1

Vapo

rPr

essu

re(m

m

Hg a

t20

°C) 1

,4

Met

hyl i

odid

eCH

3IHe

avie

rn/

an/

an/

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