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MSHA 2202

Mine GasesTraining Module –Advanced/RefresherMine RescueNovember 1981

Northern Mine RescueAssociation

INTRODUCTION

Under normal conditions, many gasesare present in the mine. The minesventilation system is designed to bringin fresh air to disperse and removeharmful gases and to supply oxygen.But during a disaster, the situation maybe quite different. Fires or explosionsmay release dangerous gases into theatmosphere. And, a disruptedventilation system could result in anoxygen-deficient atmosphere and/or abuildup of toxic or explosive gases

INTRODUCTION

Gas DetectionGas detection is an important part of any rescue or recoveryoperation. Your team will make frequent tests for gases as itadvances beyond the fresh air base. For your own safety,you'll want to know what harmful gases are present, howmuch oxygen is in the atmosphere, and whether or not gaslevels are within the explosive range.Knowing what gases are present and in what concentrationsprovides you with important clues as to what has happened inthe mine. Test results can also give you an idea about existingconditions.For example, if you get carbon monoxide (CO) readings thatindicates there's probably a fire. The amount of carbonmonoxide indicates something about the extent of that fire.

Gas Detector Requirements

Each mine rescue station is required bylaw to have two gas detectorsappropriate for detecting each type ofgas that may be encountered in themine, and either two oxygen indicatorsor two flame safety lamps.

Visual 1

Portable Gas Detectors

The type of gas detection equipmentmost often used by mine rescue teamsis the portable gas detector. Portablegas detectors include such devices ascarbon monoxide (CO) detectors,multi- gas detectors used inconjunction with various tubes, andmethane monitors used in mines withmethane. The team uses these devicesto test the mine air repeatedly as itadvances beyond the fresh air base.

Air Sampling and ChemicalAnalysis

Another way to test for gases is tocollect air samples in special syringes,evacuated bottles (bottles from whichthe air has been removed) or gas orliquid displacement containers. Thesesamples are then sent to a laboratoryfor chemical analysis. Chemical analysisis also sometimes performed at themine site with portable equipment.


Chemical analysis is generally a moretime- consuming process than testingwith a portable device, but itsadvantage is accuracy. A chemicalanalysis tells exactly what gases thesample contains, and in precisely whatamounts.

Visual 2


A complete chemical analysis can alsoreveal the presence of gases thatportable detectors are not designed todetect.Air samples aren't taken as often asportable detector readings, but they'restill an important part of rescue andrecovery operations. For example, youmay be required to take air samplesfrom ventilation shafts and exhaustairways.


This method is often used to getinformation about existing conditionsprior to sending teams underground.Air samples taken from behind sealedareas of the mine are analyzed todetermine when it's safe to beginrecovery work.

Objective 1

The team members will identify thefollowing terms:

Specific gravityExplosive rangeToxicityAsphyxiateSolubility

BASIC GAS PRINCIPALS

In order to test for gases and tounderstand what the test readingsmean, you should first know a littleabout the characteristics and propertiesof gases. After we've discussed thesegeneral principles, we'll talk aboutspecific gases you might encounterduring rescue and recovery work.

Description

To help you understand what a gas is,let's compare it with a liquid and a solid.A solid has a definite shape and volume.A liquid has a definite volume, butchanges shape according to the shapeof its container.However, a gas is a substance withneither a definite shape nor volume. Itexpands or contracts to fill the area inwhich it's contained.

Visual 3

Diffusion of Gases

The volume of a gas changes inresponse to any change in atmosphericpressure or temperature. For example:

An increase in pressure causes a gas to contract.An increase in temperature causes a gas toexpand.A decrease in pressure causes a gas to expand.A decrease in temperature causes a gas tocontract.

Diffusion of Gases

The gas's rate of diffusion is also affected bythe ventilating air currents in the mine. Therate of diffusion is greatly increased by highervelocities of air currents or by turbulence inthe air.Knowing the effects of air current,temperature, and pressure on a gas will helpyou determine its rate of diffusion. The rate ofdiffusion is how quickly the gas will mix orblend with one or more other gases and howquickly it can be dispersed.

Atmospheric Pressure and Its Effectson Rate of Diffusion

Pressure exerted on a gas is usuallyatmospheric pressure. Atmosphericpressure is measured on a barometer. Arise in the barometric reading indicatesan increase in pressure. A drop inbarometric reading indicates a decreasein pressure. The atmospheric pressurevaries within a mine, just as it does onthe surface

Visual 4

Atmospheric Pressure and ItsEffects on Rate of Diffusion

Atmospheric pressure affects the diffusion rate of a gas.For example, if the barometer rises, indicating increasedpressure, gas responds by contracting.A gas that's squeezed into a smaller area like this ismore concentrated, so it diffuses more slowly. As youmight guess, it's much easier for concentrations ofexplosive gases to build up when the barometricpressure is high. And it is harder to disperse the gasesby means of the mine's ventilation system.On the other hand, when barometric pressure falls, thepressure on the gas is reduced. The gas responds byexpanding. Once the gas expands, it is lessconcentrated, so it diffuses more quickly.

Temperature and Its Effects onRate of Diffusion

It's important to understand howtemperature affects the rate of diffusionof a gas. High temperatures (or heat)cause gases to expand, so they diffusemore quickly. Consequently, heat froma fire in the mine will cause gases toexpand and be dispersed more easily.Lower temperatures work the oppositeway: Gases respond to cold bycontracting and by diffusing moreslowly.

Visual 5

Specific Gravity or RelativeWeight

Specific gravity is the weight of a gascompared to an equal volume of normalair under the same temperature andpressure. (This is also referenced to as"relative weight")The specific gravity of normal air is 1.0.The weight of air acts as a referencepoint from which we measure therelative weight of other gases. Forexample, a gas that is heavier than airhas a specific gravity higher than 1.0. Agas that is lighter than air will have aspecific gravity less than 1.0.

Visual 6


If you know the specific gravity of a gas,you will know where it will be located inthe mine and where you should test forit.Gases issuing into still air withoutmixing tend to stratify according to thegas's specific gravity. Light gases ormixtures tend to stratify against theback and heavy gases or mixtures tendto stratify along the floor.


Sulfur dioxide, for example, has aspecific gravity of 2.2638. This is muchheavier than normal air. Knowing this,you can predict that sulfur dioxide willcollect in greater concentrations nearthe bottom or in low areas of a mine.This is why you test for sulfur dioxide inlow areas of the mine.


If the weight of a gas you're testing foris lighter than normal air, you'll know totest for it near the back of the mine.That's because lighter gases tend torise, so you can expect to find them ingreater concentrations in high areas ofthe mine.


Besides helping you determinewhere to test for a gas, specificgravity also indicates how quicklythe gas will diffuse and how easilyit can be dispersed by ventilation.


In still air, the ordinary process ofdiffusion is a very slow process.However, under usual mineconditions, ventilating air currentsand convection currents producedby temperature differences cause arapid mechanical mixing of gaseswith air. And once the gases aremixed they will not separate orstratify again.


Light gases, such as hydrogen, diffuse rapidly andare fairly easy to disperse. Heavier gases such assulfur dioxide and carbon dioxide don't diffuserapidly, so they're more difficult to disperse. It'smuch easier to remove a concentration of a lightgas like hydrogen by ventilation than it is toremove the same concentration of a heavier gaslike sulfur dioxide.Specific gravity is not the only factor thatdetermines how quickly a gas will diffuse ordisperse. Temperature and pressure also affect it.

Visual 3 & 4


Remember that an increase intemperature makes a gas diffusemore rapidly. A decrease intemperature slows down the rate ofdiffusion.Atmospheric pressure works justthe opposite: An increase inpressure slows down the rate ofdiffusion. A decrease in pressurespeeds it up.

Explosive Range andFlammability

A gas that will burn is said to be "flammable".Any flammable gas can explode under certainconditions. In order for a flammable gas toexplode, there must be enough of the gas inthe air, enough oxygen, and a source ofignition.The range of concentrations within which agas will explode is known as its explosiverange". Figures representing the higher andlower limits of the explosive range areexpressed in percentages.

Explosive Range andFlammability

The amount of oxygen that must bepresent for an explosion to occur is alsoexpressed as a percentage. When thenecessary oxygen concentrationapproaches that found in normal air,the level is expressed simply as "normalair".The explosive range of hydrogen, forexample, is 4.0 to 74.2 percent in thepresence of normal air.

Solubility

Solubility is the ability of a gas to bedissolved in water. Some gases found inmines are soluble and can be releasedfrom water. Sulfur dioxide andhydrogen sulfide, for example, arewater- soluble gases. Both may bereleased from water.

Solubility

Solubility is an important factor toconsider during recovery operations.When a mine is sealed off for anylength of time, water can collect in it.This water may have occurred naturally,or it may have been introduced duringfirefighting.

Solubility

Whatever the case, pools of water canrelease water- soluble gases into theair when they are stirred up. Pumpingwater from such pools, or walkingthrough them, can release largeamounts of soluble gases, which wouldnot otherwise be found in the mineatmosphere.

Color/Odor/Taste

Color, odor, and taste are physicalproperties that can help you identify agas, especially during barefacedexploration. Hydrogen sulfide, forexample, has a distinctive "rotten egg"odor. Some gases may taste bitter oracid; others sweet. The odor of blastingpowder fumes, together with areddish- brown color, indicates thereare oxides of nitrogen present.

Color/Odor/Taste

Of course, you can't rely on only yoursenses to positively identify a gas.Only detectors and chemical analysiscan do that. And many hazardous gases,such as carbon monoxide, have no odor,color, or taste. But keep theseproperties in mind as we discuss eachgas you may encounter in the mine.One or more of these properties may beyour first clue that a particular gas ispresent.

Health Hazards - ToxicGases

Some gases found in mines are toxic(poisonous). This can refer either towhat happens when you breathe thegas, or what happens when the gascomes into contact with exposed areasof your body.

Visual 7


The degree to which a toxic gaswill affect you depends on threefactors:

(1) How concentrated the gas is,(2) How toxic (poisonous) the gas is,and(3) How long you're exposed to thegas.


Some toxic gases are harmful to inhale.A self- contained breathing apparatus(SCBA) will protect you from such gases,as long as your face- to- face pieceseal is tight.


Other toxic gases harm the skin or canbe absorbed by the skin. As you mightguess, an SCBA won't protect you fromsuch gases. If you wear your SCBA inpetroleum-based fumes for prolongedor successive periods, the fumes caneventually permeate its rubber parts sothat the apparatus no longer providesyou with adequate protection. Yourteam may be forced to leave an areawhere such gases are detected.

Asphyxiating Gases

"Asphyxiate" means to suffocate orchoke. Asphyxiating gases causesuffocation. They do this by displacingoxygen in the air, thus producing anoxygen- deficient atmosphere. Sinceyour self- contained breathingapparatus supplies you with oxygen, itwill protect you against asphyxiatinggases.

Review Questions:

1. How do temperature andpressure affect a gas, and how dothese factors affect mine rescue?2. What is specific gravity?

Review Questions:

3. What can you determine if youknow the specific gravity of aparticular gas?4. What is the explosive range of agas and when is it important forrescue team members to know theexplosive range of gases theyencounter?

Review Questions:

5. What is a toxic gas?6. How can you protect yourselffrom toxic gases?

Review Questions:

7. How does an asphyxiating gasproduce an oxygen-deficientatmosphere?8. How do you protect yourself inan oxygen-deficient atmosphere?

Review Questions:

9. Why is it important for you toknow about the solubility of certaingases in water?10. Why should you know about thecharacteristic color, odor, and tasteof gases you may encounter?

Review Questions (ANSWERS):

1. How do temperature and pressureaffect a gas, and how do these factorsaffect mine rescue?

Temperature increases cause expansion.Temperature decreases cause contraction.Pressure increases causes contraction. Pressuredecreases cause expansion. Implication: thesefactors affect the diffusion rate of gases in themine.

2. What is specific gravity?The specific gravity (or relative weight) of a gasis its weight in relation to an equal amount ofnormal air under the same temperature andpressure.

3. What can you determine if you knowthe specific gravity of a particular gas?

Specific gravity determines where the gas willstratify in still air in the mine (whether it willrise or fall). It also determines how easily a gascan be diffused or flushed out of the mine byventilation.

4. What is the explosive range of a gasand why is it important for rescue teammembers to know the explosive range ofgases they encounter?

The explosive range of a gas is theconcentrations within which a flammable gascan explode when there is a specific amount ofoxygen present. It's important for you to knowthe explosive ranges of gases you encounterand the amount of oxygen necessary for anexplosion so you will immediately know whenyou encounter a potentially explosiveatmosphere.

5. What is a toxic gas?A gas that is poisonous

6. How can you protect yourself fromtoxic gases?

Wearing a self-contained breathing apparatus(SCBA) will protect you from many of them.However, a SCBA does not provide you withprotection against gases that attack the skin orenter the body through the skin. It will also notprovide protection if you wear it for prolongedor successive periods in petroleum-based fumesbecause such fumes may permeate the rubber.In the presence of such gases, your team maybe forced to leave the area of the mine wheretheir located.

7. How does an asphyxiating gas producean oxygen-deficient atmosphere?

By displacing oxygen,

8. How do you protect yourself in anoxygen-deficient atmosphere?

Wear an SCBA, which supplies you with oxygen.

9. Why is it important for you to knowabout the solubility of certain gases inwater?

Gases dissolved in water can be liberated inlarge quantities when mine rescue teamsdisturb the water by walking through it, or bybeginning pumping operations.

10. Why should you know about thecharacteristic color, odor, and taste ofgases you may encounter?

The characteristic color and, if the team isbarefaced, odor or taste of a gas may be thefirst clue a rescue team has that the gas ispresent in the mine atmosphere.

Objective 2:

The team members will identify thephysical properties and characteristicsof each gas they may encounterfollowing a fire, explosion, inundation,or other disaster, identify where suchgases might be found, how to detectthem, and explain the meanings of theirfindings.

MINE GASES AND THEIRDETECTION

Normal AirThe air we breathe is actually a mixture ofgases. Clean, dry air at sea level is made upof 78 percent nitrogen and 21 percentoxygen. The remaining 1 percent is madeup of argon, carbon dioxide, and smalltraces of other gases.Air is normally colorless, tasteless, andodorless. It supplies us with the oxygennecessary for life. During the day-to-dayoperations of a mine, however, normal aircan become contaminated.

Visual 8

Normal Air

For example, the carbon dioxide andwater vapors miners exhale duringrespiration are contaminants.Forces exerted on the mine's back, side,floor, and face during blasting mayallow trapped gas pockets to escapeinto the mine air. Blasting may alsoproduce pollutants such as carbonmonoxide, hydrogen sulfide, and oxidesof nitrogen.

Normal Air

Even internal combustion engines andbattery charging stations can besources of contamination because theycan produce hazardous fumes.

Normal Air

Normally, these contaminants arecarried away by the mine's ventilationsystem. But during a disaster situation,the mine's ventilation system may bepartially or totally disrupted.Fires and explosions can disruptventilation by damaging ventilationcontrols. Falls and rock bursts candisrupt ventilation by obstructing theflow of air.

Normal Air

In addition, the disaster itself mayprovide additional sources ofcontamination. Fires and explosions, forexample, often produce dangerousgases. And inundations may releasewater- soluble gases

Normal Air

The gases present in the mine followinga disaster will vary according to thetype of the disaster situation and mine.What type of equipment is used in themine (electrical, compressed air, ordiesel) will also affect what gases arepresent.

Normal Air

However, for all mines, rescue teamsmust know how to test for oxygendeficiency and carbon monoxide.In addition to this, the team may haveto know how to test for hydrogensulfide, oxides of nitrogen, and so on.You should know how to test for all thegases that may be present in the minesin which you will be working as a minerescue team.

Normal Air

The gases present in the mine followinga disaster will vary according to thetype of the disaster situation and mine.What type of equipment is used in themine (electrical, compressed air, ordiesel) will also affect what gases arepresent.However, for all mines, rescue teamsmust know how to test for oxygendeficiency and carbon monoxide.

Normal Air

In addition to this, the team may haveto know how to test for hydrogensulfide, oxides of nitrogen, and so on.You should know how to test for all thegases that may be present in the minesin which you will be working as a minerescue team.

Visual 9Gas Chemical

Symbol Specific Gravity

Explosive Range Health Hazards Solubility Color Odor Taste

Air -- 1.000 -- -- -- -- -- Oxygen O2 1.1054 Supports Combustion Oxygen deficiency:

17% panting 15% dizziness and headache 9% unconsciousness 6& death

Moderate -- -- --

Nitrogen N2 0.9674 -- Asphyxiant (O2 Depletion) Slight -- -- -- Carbon Dioxide

CO2 1.5291 -- Increases breathing rate. May cause death in high concentrations.

Soluble -- -- Acid in high concentrations

Carbon Monoxide

CO 0.9672 12.5 to 74.2% Highly toxic. Can be an Asphyxiant.

Slight -- -- --

Nitrogen Dioxide

NO2 N2O4

1.5894 -- Highly toxic. Corrosive effect on lungs. Can be an Asphyxiant.

Only Slight Reddish Brown

Blasting powder fumes

Blasting powder fumes

Hydrogen H2 0.0695 4.0 to 74.5% Highly Explosive

Asphyxiant (O2 Depletion) -- -- -- --

Hydrogen Sulfide

H2S 1.1906 4.3 to 45.5% Highly toxic. Can be an Asphyxiant.

Soluble -- Rotten Eggs Sweetish

Sulfur Dioxide SO2 2.2638 -- Highly toxic. Can be an Asphyxiant.

Highly -- Sulfurous Acid (bitter)

Methane CH4 0.5545 5 to 15% Asphyxiant (Rare) Slight -- -- -- Ethane C2H6 1.0493 3.0 to 12.5% Asphyxiant (Rare) Slight -- -- -- Propane C3H8 1.5625 2.12 to 9.35% Asphyxiant (Rare) Slight -- “Gassy” in

high concentrations

--

Butane C4H10 2.0100 1.86 to 8.41% Asphyxiant (Rare) Slight -- “Gassy” in high concentrations

--

Acetylene C2H2 0.9107 2.5 to 80% Only slightly toxic. Asphyxiant (Rare)

Only Slight -- -- Garlic

Radon Rn 7.526 -- Exposure to radiation. Highly -- -- --

Visual 10Gas Detection Method When to Test

Oxygen (O2) Oxygen indicator, flame safety lamp, Chemical analysis

During any team exploration.

Nitrogen (N2) Chemical analysis When an O2 deficient atmosphere is suspected. In mines where nitrogen issues from rock strata. In inactive areas where ventilation has been inadequate

Carbon Dioxide (CO2) CO2 Detector, Multi-gas Detector, Chemical analysis

After a fire or explosion. When entering abandoned areas. When reopening sealed areas.

Carbon Monoxide (CO) CO Detector, Multi-gas Detector, Chemical analysis

During any team exploration. Especially when fire is suspected.

Nitrogen Dioxide (NO2) NO2 Detector, Multi-gas Detector, Chemical analysis

After mine fire or explosion. When diesel equipment is used. After detonation of explosives.

Hydrogen (H2) Multi-gas Detector, Chemical analysis

After mine fire or explosion. Near battery charging stations. When steam is produced by water, mist, or foam firefighting.

Hydrogen Sulfide (H2S) H2S Detector, Multi-gas Detector, Chemical analysis

In poorly ventilated areas. During unsealing operations. Following mine fires.

Sulfur Dioxide (SO2) SO2 Detector, Multi-gas Detector, Chemical analysis

When standing water is disturbed. After mine fire or explosion and when reopening sealed areas of the mine after mine fires.

Methane (CH4) CH4 Detector, Multi-gas Detector, Chemical analysis

During any team exploration. When normal ventilation is disrupted. When entering abandoned workings.

Heavy Hydrocarbons Ethane (C2H6) Butane (C3H8) Propane (C4H10)

Multi-gas Detector, Chemical analysis

Following fires or explosions when CH4 is present. Following accidental entry into adjacent oil or gas well casings.

Acetylene (C2H2) Multi-gas Detector, Chemical analysis

Following a methane explosion in air which is low in O2

Radon (Rn) Survey Meter When normal ventilation is disrupted and during unsealing operations.

Visual 11

Oxygen (02)

Specific Gravity: 1.1054Explosive Range and Flammability:Oxygen is not an explosive gas, but itdoes support combustion.

Oxygen (02)

Health Hazards:Oxygen found in normal air is nontoxic.In fact, it is essential for life.It is harmful to breathe air that is low in oxygen,and breathing extremely oxygen deficient aircan kill you.For example, you're accustomed to breathingair containing about 21 percent oxygen.

Oxygen (02)

Health Hazards (continued):When the oxygen content of air drops to about17 percent, you'll begin to breathe faster anddeeper because your body is trying tocompensate for the lack of oxygen.A 15 percent concentration will cause dizzinessand headaches.If the oxygen content of the air you're breathingdrops as low as 9 percent, you may loseconsciousness.A 6 percent concentration or less is almostalways fatal.

Oxygen (O2)

There are four main causes of oxygendeficiency in the mine:

(1) Insufficient or improper ventilation whichfails to bring enough oxygen to the work area,(2) Displacement of the air's oxygen by othergases,(3) A fire or explosion that consumes oxygen,and(4) Consumption of oxygen by workers.

Oxygen (02)

Solubility: Moderately soluble in water.Color/Odor/Taste: Colorless, odorless,and tasteless.Cause or Origin: Oxygen is the secondlargest component of normal air. About21 percent of normal air is oxygen.

Oxygen (02)

Detection Methods: To detectoxygen- deficient atmospheres, useeither an oxygen indicator or flamesafety lamp. Since oxygen is onlyslightly heavier than air, hold yourportable detector at waist level whenyou test for oxygen deficiency.Chemical analysis will also detectoxygen deficiency.

Oxygen (02)

When to Test: During exploration, testas often as necessary to determinewhether the atmosphere isoxygen- deficient.

Oxygen (02)

Meaning of Findings: If the main fan isstill operating, an oxygen- deficientatmosphere could indicate that anexplosion has taken place, or that a firesomewhere in the mine is consumingoxygen. Oxygen deficiency may alsoindicate that the mine's ventilationsystem has been disrupted.

Nitrogen (N2)

Specific Gravity: 0.9674Explosive Range and Flammability:Nitrogen is not an explosive gas and itwill not burn.Heath Hazards: Nitrogen is nontoxic.However, in above- normalconcentrations it acts as an asphyxiatebecause it lowers the oxygen content ofthe air.

Nitrogen (N2)

When to Test: Test for nitrogen whenyou suspect that the atmosphere isoxygen- deficient and in abandoned orinactive workings where ventilation isinadequate. Also test for it in mineswhere nitrogen is known to issue fromrock strata.Meaning of Findings: An elevatednitrogen content indicates anoxygen- deficient atmosphere.

Nitrogen (N2)

Cause or Origin: Normal air containsapproximately 78 percent nitrogen,making nitrogen the largest componentof normal air.Nitrogen can issue from the strata insome metal mines. Another source ofnitrogen in underground mines is thedetonation of explosives

Nitrogen (N2)

Where Found: Increased nitrogen levelsare often present after explosives havebeen detonated.Detection Method: Chemical analysis.

Visual 12

Carbon Dioxide (CO2)

Specific Gravity: 1.5291Explosive Range and Flammability:Carbon dioxide will neither burn norexplode.


Health Hazards: Normal air containsabout 0.03 percent carbon dioxide.

When it is present in high concentrations (2percent or higher), carbon dioxide causesyou to breathe deeper and faster.Breathing air containing 5 percent carbondioxide increases respiration 300 percent,causing difficult breathing.Breathing air containing 10 percent carbondioxide causes violent panting and can leadto death.


Solubility: Carbon dioxide is soluble in water.Color/Odor/Taste: Carbon dioxide is colorlessand odorless. High concentrations mayproduce an acid taste.Cause or Origin:

Carbon dioxide is a normal component of air.It is a product of complete combustion (burning).Oxidation and the decay of timbers, also producescarbon dioxide.Carbon dioxide is also a by- product of therespiration (breathing) process.


Fires, explosions, and blastingoperations produce CO2. In some mines,it is liberated from the rock strata.Where Found: Because it's relativelyheavy, CO2 will be found in greaterconcentrations along the floor and inlow places in the mine. It also oftenshows up in abandoned workings,during fires, and after an explosion ordetonation of explosives.


Detection Methods:You can use a carbon dioxide detector, amulti- gas detector, or chemical analysis totest for carbon dioxide.Because CO2 tends to collect near the minefloor, hold your portable detector low.

When to Test:Test for CO2 after a fire or explosion.Also test for it when you're entering aninactive area of the mine or reopening asealed area.


Meaning of Findings:Elevated CO2 readings may indicate that afire or explosion has taken placesomewhere in the mine.High readings may also indicate anoxygen- deficient atmosphere.

Visual 13

Carbon Monoxide (CO)

Specific Gravity: 0.9672Explosive Range and Flammability:Carbon monoxide is explosive andflammable. Its explosive range innormal air is 12.5 to 74.2 percent.Health Hazards: Carbon monoxide ishighly toxic even in very lowconcentrations. Exposure to as little as.15 to .20 percent CO is extremelydangerous.


Carbon monoxide is so toxicbecause it combines easily withyour red blood cells (hemoglobin)- the cells that normally carryoxygen to your body's tissues.


Once the cells have taken up CO, theyno longer have the capacity to carryoxygen.


It doesn't take much CO to interferewith your blood's oxygen- carryingcapacity because the gas combines withhemoglobin 200 to 300 times morereadily than oxygen.


The first symptom of carbon monoxidepoisoning is:

A slight tightening across your forehead andpossibly a headache. Carbon monoxidepoisoning is cumulative over time. As youcontinue to be exposed to it, the poisoningeffects build up accordingly.As little as 500 PPM (0.05 percent) can killyou in three hours.If you're exposed to a high COconcentration, you may experience very fewsymptoms before losing consciousness.


Solubility: Carbon monoxide is slightlysoluble in water.Cause or Origin: Carbon monoxide is aproduct of the incomplete combustionof any carbon material. It is producedby mine fires and explosions of gas.Carbon monoxide is also produced bythe burning or detonation of explosives,and it is emitted from the exhaust ofinternal combustion engines.


Where Found: Carbon monoxide is foundduring mine fires and after explosions ordetonations of explosives. It can also usuallybe detected near internal combustion engines.Detection Methods: Carbon monoxide can bedetected by means of carbon monoxidedetectors, multi-gas detectors, or by chemicalanalysis. Since CO is slightly lighter than air;hold your portable detector at chest level.


When to Test: During any teamexploration, test as often as necessaryto determine the atmosphere's COcontent. Do this especially if fire issuspected.Meaning of Findings: The presence ofCO for a continued period of timedefinitely indicates there is a firesomewhere in the mine.

Visual 14

Oxides of Nitrogen

Nitric Oxide (NO) - Nitrogen Dioxide(NO2 or N2O4)Specific Gravity: (NO2) - 1.5894Explosive Range and Flammability: NO2Will neither burn nor explode.

Oxides of Nitrogen

Health Hazards: Oxides of nitrogen arehighly toxic. Breathing even smallamounts will irritate your throat. Whenmixed with the moisture in your lungs,they form acids that corrode yourrespiratory passages and cause them toswell. Often, such symptoms don't showup until several hours after you'reexposed to the gas.

Oxides of Nitrogen

Exposure to .01 to .015 percent can bedangerous for even short exposures.And .02 to .07 percent can be fatal forshort exposures. If exposure has beensevere, the victim may die, literallydrowned by water that has entered thelungs from the body in an attempt tocounteract the corrosive effects of theacids formed by the oxides of nitrogen.

Oxides of Nitrogen

Solubility: Very slight solubility in water.Color/Odor/Taste: Oxides of nitrogenare colorless at low concentrations andbecome reddish- brown at higherconcentrations. They smell and tastelike blasting powder fumes.

Oxides of Nitrogen

Cause or Origin: Oxides of nitrogen areproduced by burning and by thedetonation and burning of explosives.They are also emitted from the exhaustof diesel engines. In the presence ofelectrical arcs or sparks, nitrogen in theair combines with oxygen (oxidizes) toform oxides of nitrogen.

Oxides of Nitrogen

Where Found: Because they're heavierthan air, oxides of nitrogen tend tocollect in low places in the mine. Theycan be found when electricalmalfunctions produce arcs or sparks,and after blasting operations.

Oxides of Nitrogen

Detection Methods: To test for nitrogendioxide, you can use a nitrogen dioxidedetector, a multi- gas detector, orchemical analysis. Hold portabledetectors low when you test for theserelatively heavy gases. Theircharacteristic reddish- brown color maybe another indication that there isnitrogen dioxide present.

Oxides of Nitrogen

When to Test: Test for oxides ofnitrogen following a fire or explosionand after the detonation of explosives.Since diesel exhaust is a source ofthese gases, test in areas where dieselequipment is used.

Oxides of Nitrogen

Meaning of Findings: High NO2 readingscould indicate there has been a fire orthat explosives are burning.Malfunctioning electrical equipmentproducing arcs or sparks could also bethe source. If diesel equipment iscausing the elevated NO2 readings, thatindicates ventilation is inadequate.

Visual 15

Hydrogen (H2)

Specific Gravity: 0.0695Explosive Range and Flammability:Hydrogen is a highly explosive gas.Air containing 4 to 74.2 percent hydrogen willexplode even when there is as little as 5 percentoxygen present.Very violent explosions are possible when aircontains more than 7 to 8 percent hydrogen.The presence of small quantities of hydrogen greatlyincreases the explosive range of other gases.

Hydrogen (H2)

Health Hazards: At high concentrations,hydrogen can replace oxygen in the airand act as an asphyxiate. The mosthazardous aspect of hydrogen, however,is the fact that it is highly explosive.Solubility: Not soluble in water.Color/Odor/Taste: Colorless, odorless,and tasteless.

Hydrogen (H2)

Cause or Origin:Hydrogen is produced by the incompletecombustion of carbon materials during firesand explosions.It may also be liberated when water orsteam comes in contact with hot carbonmaterials during fire fighting.Battery charging also produces hydrogen.

Hydrogen (H2)

Where Found:You can expect to find hydrogen in the vicinity ofbattery charging stations, where explosives havebeen detonated, and after explosions.Hydrogen may also be detected during firefightingwhen either water or foam extinguishing methods isused.You can also expect to find hydrogen in an areathat's been sealed to extinguish a fire.Because hydrogen is relatively light, it tends tocollect in high places.

Hydrogen (H2)

Detection Methods: Hydrogen can bedetected with a multi- gas detector, orby means of chemical analysis. Holdportable detectors high.

Hydrogen (H2)

When to Test: Test for hydrogen afterany fire or explosion and near batterycharging stations in the mine. Also testfor it when water, water mists, or foamare used to fight fires.

Hydrogen (H2)

Meaning of Findings: The presence ofhydrogen could indicate that a fire orexplosion has taken place. Firefightingwith water or foam could also beproducing the hydrogen. Elevatedreadings could also indicate that thereis inadequate ventilation around batterycharging stations.

Visual 16

Hydrogen Sulfide (H2S)

Specific Gravity: 1.1906Explosive Range and Flammability:Hydrogen sulfide is flammable andexplosive in concentrations from 4.3 to45.5 percent in normal air. It is mostexplosive at 14.2 percent.


Health Hazards:Hydrogen sulfide is one of the mostpoisonous gases known.In low concentrations (.005 to .010 percent)hydrogen sulfide causes inflammation of theeyes and respiratory tract.Slightly higher concentrations (0.02 to 0.07percent) can lead to bronchitis orpneumonia.


Health Hazards:Higher concentrations (0.07 to 0.10 percent)can cause rapid unconsciousness, cessationof respiration, and death.And 0.10 to 0.20 percent or more can causerapid death.


Solubility: Soluble in water.Color/Odor/Taste: Hydrogen sulfide iscolorless, has the odor of rotten eggs,and a slight sweetish taste.


Cause or Origin:Hydrogen sulfide is produced when sulfur compoundsdecompose.It is found in certain oil and gas fields and in some gypsummines.It also may be liberated from methane feeders in mineswith methane.Hydrogen sulfide is often liberated when acid mine watercorrodes metallic sulfides.It can also be released from mine water, which containsthe gas in solution.Heating sulfides in the presence of moisture (as in minefires) may also produce the gas.Blasting in sulfide ores can also liberate hydrogen sulfide.


Where Found:Hydrogen sulfide is found in low places of themine because it is a relatively heavy gas.It's also often found in pools of water.In some mines, it may be found near oil or gaswells.Hydrogen sulfide may also be detected duringmine fires.Since it is a water- soluble gas, hydrogensulfide is often liberated from water in sealedareas of the mine when recovery crews walkthrough the water or begin pumping operations.


Detection Methods:You can test for hydrogen sulfide with ahydrogen sulfide detector, a multi- gasdetector, and by chemical analysis.Because H2S is relatively heavy, hold yourportable detector low when you're testingfor this gas.You may recognize H2S by its distinctive"rotten egg" odor.


Detection Methods:However, continued exposure to the gas willdull your sense of smell, so this may notalways be a reliable detection method.Eye irritation is another indication thathydrogen sulfide is present.


When to Test: Test for hydrogen sulfidein poorly ventilated areas of the mine,during unsealing operations, andfollowing mine fires


Meaning of Findings: A buildup ofhydrogen sulfide could indicate thatventilation is inadequate. It may also beproduced by seepage from an oil or gaswell. The presence of hydrogen sulfidemight also indicate that excess water isaccumulating in sealed or inaccessibleareas of the mine.

Visual 17

Sulfur Dioxide (SO2)

Specific Gravity: 2.2638Explosive Range and Flammability: Will notburn or explode.Health Hazards:

Sulfur dioxide is a very toxic, irritating gas that isdangerous even in small concentrations.As little as 0.04 to 0.05 percent is dangerous to life.Even very tiny amounts of sulfur dioxide (.001 percent orless) will irritate your eyes and respiratory tract.Larger concentrations can cause severe lung damage andmay cause respiratory paralysis and the complete inabilityto breathe.


Solubility: Highly soluble in water.(Sulfur dioxide is one of the mostsoluble gases found in mines.)Color/Odor/Taste: Sulfur dioxide iscolorless, but it has a bitter, acid tasteand a strong sulfurous odor.


Cause or Origin: Sulfur dioxide may beproduced by blasting in sulfide ores andby fires containing iron pyrite(commonly known as "fool's gold").Sulfur dioxide may be released duringthe burning of some diesel fuels and bysulfide ore dust explosions


Where Found: Because it is relativelyheavy, sulfur dioxide tends to collect inlow places in the mine and near sumps.You can expect to find it after somefires or explosions.Other Information: Because of its highspecific gravity, sulfur dioxide is hard todisperse by ventilation.


Detection Methods: You may test forsulfur dioxide by means of a multi- gasdetector or by chemical analysis.Because sulfur dioxide is a relativelyheavy gas, hold portable detectors lowwhen you test for it. Sulfur dioxide'sdistinctive odor and taste, and therespiratory tract and eye irritation you'llexperience when exposed to it are alsoreliable indicators of its presence. .


When to Test: Because it's highlysoluble in water, test for sulfur dioxidewhen stagnant water is disturbed. Testfor this gas following fires or explosions,and when sealed areas of the mine areopened after mine fires.Meaning of Findings: High SO2 readingscould indicate a mine fire or a sulfideore dust explosion.

Visual 18

Methane (CH4)

Specific Gravity: 0.5545Explosive Range and Flammability:

Methane is flammable.Its explosive range is 5 to 15 percent whenthere is at least 12.1 percent oxygen.Methane is most explosive, however, in the9.5 to 10 percent range.

Methane (CH4)

Explosive Range and Flammability:Methane's explosive range is not anabsolute measure of safety.There are other important factors to takeinto consideration.For example, the presence of othercombustible gases with wider explosiveranges or lower ignition points thanmethane may result in a more highlyexplosive mixture.

Methane (CH4)

Health Hazards: Methane is not toxic.In high concentrations, however, it cancause asphyxiation by lowering theoxygen content of normal air. The mostdangerous aspect of methane is the factthat it is explosive.Solubility: Slightly soluble in water.Color/Odor/Taste: Colorless, odorless,tasteless.

Methane (CH4)

Cause or Origin:Methane may be liberated from the strata inmetal/nonmetal mines when carbonaceous shale ispenetrated, and occasionally when carbonaceousrock is contacted or is in the vicinity.Methane can issue in large quantities from suddenoutbursts or from feeders or blowers or clay veins insome mines.Methane can also be liberated by the decompositionof timbers and when water is removed from the mine.

Methane (CH4)

Where Found:Because methane is relatively light, itcollects in high places, so you can expect tofind it near the back of the mine.You also may find it at freshly mined areas,in poorly ventilated areas, and inabandoned or unused sections of the mine,especially where timbering is extensive.Because it is a relatively light gas (lowspecific gravity), methane is usually easy todisperse and remove from the mine bymeans of ventilation.

Methane (CH4)

Detection Methods: To test for methane,use a methane detector or chemicalanalysis. Remember that methane is alight gas; so hold your portable detectorhigh.

Methane (CH4)

Where to Test: In mines wheremethane is possible, test as often asnecessary during exploration todetermine the methane content of thesurrounding atmosphere. Also test formethane when normal ventilation isdisrupted and when you are enteringabandoned workings or removing waterfrom old workings.

Methane (CH4)

Meaning of Findings: If methane ispresent, it's important to monitor itcarefully because it is potentiallyexplosive if there is enough oxygenpresent. If methane exists in potentiallyexplosive concentrations or incombination with other gases thatextend its explosive range, your teammay be required to leave the mine.

Heavy Hydrocarbons

Ethane (C2H6)Propane (C3H8)Butane (C4H10)

Heavy Hydrocarbons

Specific Gravity: Ethane 1.0493Propane 1.5625Butane 2.0100

Heavy Hydrocarbons

Explosive Range and Flammability:Ethane - from 3 to 12.5 percent innormal air.Propane - from 2.12 to 9.35 percent innominal air.Butane - from 1.86 to 8.41 in normalair.

Heavy Hydrocarbons

Health Hazards: These gases are nottoxic. At high concentrations they candisplace enough oxygen to cause deathby asphyxiation, but you'll rarely findthem in such high concentrations inmines.

Heavy Hydrocarbons

Solubility: All three are slightly solublein waterColor/Odor/Taste: All three arecolorless and tasteless. In certainconcentrations, propane and butanemay produce a characteristic "gassy"odor. Ethane is odorless.

Heavy Hydrocarbons

Cause or Origin: After mine fires, smallconcentrations of these gases are oftendetected along with methane in minesthat have methane. They alsosometimes leak from gas or oil wells.

Heavy Hydrocarbons

Where Found: The heavy hydrocarbonsare often found in mines adjacent to oilor gas wells. Because they are heavy,these gases collect in low areas of themine.Detection Methods: You can detectethane, propane, and butane with aportable detector or by chemicalanalysis. Because these gases arerelatively heavy, hold your portabledetector low when you test for them.

Heavy Hydrocarbons

When to Test: Test for these gasesfollowing fires or explosions whenmethane is present. You should alsotest for the heavy hydrocarbons if oil orgas casings are accidentally enteredduring mining operations.

Heavy Hydrocarbons

Meaning of Findings: In significantconcentrations, the heavy hydrocarbonscan extend methane's explosive range ifthe mine has methane. Elevatedreadings could indicate there has beena methane explosion, if this is possiblein the mine, or that there is seepagefrom an adjacent gas or oil well.

Acetylene (C2H2)

Specific Gravity: 0.9107Explosive Range and Flammability:Acetylene is combustible but it will notsupport combustion. Its explosive rangein normal air is 2.5 to 80 percent.Health Hazards: Acetylene is slightlytoxic. In high concentrations, it cancause asphyxiation by depleting theoxygen in the atmosphere.

Acetylene (C2H2)

Solubility: Very slightly soluble in water.Color/Odor/Taste: Acetylene is colorlessand tasteless. It has a slight garlic odor.Cause or Origin: Acetylene is formedwhen methane is burned or heated inair having a low oxygen content.

Acetylene (C2H2)

Where Found: Acetylene is found aftermethane explosions in air having a lowoxygen content.Detection Methods: Test for acetylenewith a multi- gas detector or bychemical analysis. You may alsorecognize it by its characteristic garlicodor. Since acetylene's specific gravityis near that of normal air, hold portabledetectors at chest level.

Acetylene (C2H2)

When to Test: Test for acetylene after amethane explosion in air that is oxygendeficient.Meaning of Findings: The presence ofacetylene could indicate that anexplosion has taken place in an areawith a low oxygen content, such as in asealed area.

Radon (Rn)

Specific Gravity: 7.526Explosive Range and Flammability:Non-explosive and nonflammable.Health Hazards: Radon is not toxic.However radon and radon daughter’s -a decay product of radon - areradioactive and emit radiation.Continued exposure to high levels ofthese gases has been linked to theincidence of lung cancer.

Radon (Rn)

Mines are required to keep exposure toradiation below 4 WLM per year. Theexposure for any one-month is limitedto one WLM.Solubility: Radon is highly soluble inwater.Color/Odor/Taste: Colorless, odorless,tasteless.

Radon (Rn)

Cause or Origin: Radon is a gaseousdecay product of the uranium seriesand is found in all uranium mines. Itcan also be liberated, but to a lesserextent, from almost any rock or soil.

Radon (Rn)

As radon is liberated into a mineatmosphere, it continues to decay andforms airborne particles the size ofatoms called radon daughters. Radondaughters are particularly dangerous.They adhere to respirable dust, and canbe inhaled with the dust. Once inhaled,they become deposited in the lungswhere they continue to decay, giving offradiation and damaging lung tissue.

Radon (Rn)

The skin can also absorb radiation. Ifthe radiation hazard in an area is veryhigh, breathing protection andprotective clothing may be required.Where Found: Mostly in uranium mines.Stagnant air carries heaviestconcentrations. Also, pools of water willcarry radon. Radiation levels can jumpextremely fast when ventilation isdisrupted.

Radon (Rn)

Detection Methods: Survey meters areused to sample particulate matter in theair on a scheduled basis. Dosimeterscan be used to monitor an individual'sexposure. The miners can wear them.When to Test: Regular tests arerequired in uranium mines. Tests shouldbe made when ventilation is disruptedand when opening a sealed area.Meaning of Findings: Excessive readingswould indicate a disruption of

Objective 3:

The team members will identify thecomposition, physical properties, andcharacteristics of smoke, rock stratasmoke, and the damps.

SMOKE

Smoke is a result of combustion. Itconsists of tiny particles of solid andliquid matter suspended in the air. Theparticles in smoke are usually soot orcarbon, and tar- like substances suchas hydrocarbons.

SMOKE

Although smoke may irritate your lungswhen you inhale it, it is not normallyconsidered to be an asphyxiate.However, smoke usually containscarbon monoxide and other toxic orasphyxiating gases produced by fires.This is why it is so dangerous to inhalesmoke.

SMOKE

Also, if there is a sufficient amount ofhydrocarbons in the smoke, thehydrocarbons can make the smokeexplosive.

SMOKE

Besides the dangers involved in inhalingsmoke and its potential for explosion,smoke is also hazardous in anotherimportant way: The presence of smokelimits your visibility. This single factoradds an extra element of difficulty toany rescue or recovery operation.

ROCK- STRATA GAS

Rock- strata gases occur in somemetal- mining districts in the UnitedStates, particularly in Colorado andNevada.Rock- strata gas, commonly called rockgas, is assumed to be largely nitrogenand carbon dioxide. It is released fromthe rock strata under the influence ofatmospheric pressures.

ROCK- STRATA GAS

Because rock gas is largely nitrogenand carbon dioxide, the effect of rockgas is to produce an oxygen- deficientatmosphere, and this, in turn, cancause one to suffocate if breathingprotection is not worn.

THE DAMPS

"Damps" are the names early minersgave to mixtures of gases. Many ofthese terms are still in use today. Thesenames often describe what causes themixtures or how they affect miners.

THE DAMPS

The damps most commonly found inmines are:

Whitedamp: Whitedamp is a mixture of carbonmonoxide and air, which results from a minefire. It gets the name "whitedamp" from the factthat it is found in high concentrations in blackpowder smoke, which is white. The carbonmonoxide in this mixture makes it toxic.Stinkdamp: This is a mixture of hydrogensulfide and air. Stinkdamp gets its name fromthe characteristic "rotten egg" odor of hydrogensulfide. It is highly toxic and in certainconcentrations it can be explosive.

THE DAMPS

Firedamp: This is a mixture of methane andair that will burn or explode when ignited. The"fire" in firedamp comes from the fact thatthe mixture is flammable.

Review Questions

1. Name two ways in which oxygendeficiency can occur in a mine?2. What are the explosive gases thatmay occur in the mine or mines youmay be called to work in?3. Name the gases that can be detectedby color, odor, or taste, and explainwhat these identifying features are.

4. Of the gases we've talked about,which ones are toxic if you inhale them?5. What are the five major damps?Explain what each mixture contains andwhy it's dangerous?

Review Questions - ANSWERS

1. Name two ways in which oxygen deficiency canoccur in a mine?

The presence of other gases may dilute theoxygen content of the mine air. Firesand/or explosions can consume oxygen.Disrupted ventilation may result in oxygendeficiency

2. What are the explosive gases that may occur in the mine ormines you may be called to work in? (Note: Explosive ranges areincluded here so you can discuss them if you wish. Discuss theexplosive ranges of the gases that are a problem at the mine ormines your team will be serving.)

a. Carbon monoxide- 12.5 to 74.2%b. Hydrogen - 4.0 to74.2% even with aslittle as 5% oxygenpresentc. Hydrogen sulfide -4.3 to 45.5%d. Methane - 5 to 15%in at least 12.1%oxygen

e. Ethane - 3.0 to12.5%f. Propane - 2.12 to9.35%g. Butane - 1.86 to8.41%h. Acetylene - 2.5 to80%

3. Name the gases that can be detected by color,odor, or taste, and explain what these identifyingfeatures are.

a. Carbon dioxide -acid taste in highconcentrationsb. Nitrogen dioxide -reddish brown inhigher concentrations,odor and taste ofblasting powder fumesc. Hydrogen sulfide -rotten egg odor(however, continuedexposure deadensyour sense of smell),slight sweetish odor

d. Sulfur dioxide -sulfur odor, acid tastee. Propane and butane- "gassy" odor incertain concentrationsf. Acetylene - slightgarlic odor

4. Of the gases we've talked about, which ones aretoxic if you inhale them?

Carbon monoxide, oxides of nitrogen, hydrogensulfide, sulfur dioxide, and acetylene. (All of thesegases are highly toxic, with the exception ofacetylene, which is slightly toxic).

5. What are the five major damps? Explainwhat each mixture contains and why it'sdangerous?

a. Whitedamp - carbonmonoxide and air -Toxicb. Stinkdamp -hydrogen sulfide andair. Toxic, and may beexplosive.c. Afterdamp - carbonmonoxide, carbondioxide, methane,oxygen, nitrogen, andhydrogen. Toxic,explosive, and can beoxygen-deficient.

d. Blackdamp - carbondioxide, nitrogen, andair. Oxygen-deficient.Can causesuffocation.e. Firedamp - methane(5 to 15%) and air.Can explode.

GENERAL REVIEW - MINE GASES

1. Normal air contains approximately what percentoxygen?

a. 15%b. 21%c. 31%d. 79%

2. Carbon monoxide is:

a. a gas found in all mining operationsb. a normal constituent of airc. detected during a mine fire or explosiond. a product of the breathing process

3. An elevated concentration of carbon dioxide inmine air can be harmful because:

a. it is highly explosiveb. it increases the breathing ratec. it is highly toxic in small concentrationsd. all the above

4. An elevated concentration of nitrogen in mine aircan be harmful because:

a. it can lower the oxygen content of the airb. it is highly explosivec. it is highly toxicd. all the above

5. Oxides of nitrogen can occur in mine atmospheres

a. when certain explosives are usedb. when diesel-powered equipment is being usedc. when electric equipment produces are or sparksd. all the above

6. Accumulation of hydrogen in the mine atmosphereare dangerous because hydrogen:

a. is highly toxicb. is highly soluble in waterc. is highly explosived. gives off a suffocating odor

7. Characteristics of hydrogen sulfide include:

a. explosiveb. highly toxicc. can be liberated from pools of stagnant waterd. all the above

8. Which of the following is not true of sulfur dioxide

a. it is explosiveb. it is highly toxicc. it is highly soluble in waterd. it can occur during a mine fire

9. The most likely source of ethane, propane, orbutane in a mine is:

a. use of diesel equipmentb. battery charging stationsc. leakage from adjacent gas or oil wellsd. all the above

10. Acetylene would normally be found in a mineatmosphere where:

a. diesel equipment is being usedb. methane has burned or exploded in air with alowered oxygen levelc. leakage has occurred from adjacent oil or gaswellsd. battery charging stations are located

11.Match each damp with its components:

1. Firedamp

2. Blackdamp

3. Afterdamp

4. Whitedamp

5. Stinkdamp

a. Carbonmonoxide and airb. Hydrogensulfide and airc. Carbon dioxide,nitrogen and aird. Carbonmonoxide, carbondioxide, methane,oxygen, nitrogen,and hydrogene. Methane and air

12. Mine rescue teams are required by Federal lawto have available:

a. one detecting device for every gas listed asdangerous by the U.S. Bureau of Minesb. one detecting device for each gas normallyencountered in the mine(s) the team servesc. two detecting device for each gas normallyencountered in the mine(s) the team servesd. one detecting device for each team member

13. Atmospheric pressure and temperature areimportant factors because they:

a. affect the rate of diffusion of a gas byventilationb. can cause false readings on gas detectioninstrumentsc. lower oxygen content in the mined. all the above

14. Two gases that are highly soluble in water are:

a. methane and acetyleneb. hydrogen sulfide and hydrogenc. nitrogen and sulfur dioxided. hydrogen sulfide and sulfur dioxide

15. A gas that is normally found near the back or inhigh places in the mine is said to be low:

a. level of toxicityb. level of explosivityc. specific gravityd. level of solubility

16. A nontoxic gas can still be dangerous because:

a. displace oxygenb. burnc. exploded. all the above

17. Gases are neither toxic nor explosive:

a. are not found in mine atmospheresb. are not dangerousc. can be dangerous because they can displaceoxygend. cannot be detected with today's detectioninstruments