Excerpted from:

Miner's Manual: A Complete Guide to Health and Safety Protection on the Job by J. Davitt McAteer (Washington, DC: Center for Law and Social Policy, 1981), Chapter 12, pages 149-169.





Gases can be extremely dangerous in all mines.  It’s important to know which gases are most likely to be found, what kinds of effects they can have on you, which are the most dangerous, and what can be done under the law to control them.















This Chapter is not just about the danger of gases in coal mines.  It’s about your kind of mining too—where the dangers are just as real.  See especially the list of gassy NMN mines [below]  and the special section on the Sunshine Mine Disaster [below].





Bad air poses serious health and safety hazards in two ways in addition to dust:


1.  Oxygen deficiency, which causes asphyxiation (suffocation).


2.  Dangerous gases (such as methane and carbon monoxide) which can cause asphyxiation by replacing oxygen.  Gases can also cause other health hazards, and explosions.




·        Don’t go into areas where the air isn’t moving without testing it first.

·        Report any hissing sounds or strange odors to your supervisor.

·        Check air quality often where combustion engines are used.

·        When methane is present or suspected, take the special precautions outlined in the federal regulations.





Oxygen is essential to human life and air usually contains about 21 percent oxygen (most of the rest is nitrogen).  But loss of oxygen can occur in underground mines with terrible effects on miners.


Oxygen deficiency may result from fires and explosions--but oxygen is also consumed by oxidation of minerals and organic materials.  Rotting timbers and damp places may be sites of oxygen deficiency.


The law requires that your work area’s air contain at least 19.5 percent oxygen, Act 303(b).  If it goes below this, you should stop working and take steps to correct the oxygen deficiency, or to leave the area until the danger is corrected (COAL/U: 75.301; MNM/U: 57.5-15).


Effects of Oxygen Deficiency



Present            Effect



(or more)        Breathing easiest


19.5%              Minimum requirement by law


19%                 Flame safety lamp gives about one-third the light it gives in normal air (if the atmosphere is methane-free)


17%                 Breathing becomes faster and deeper


16.25%            Flame safety lamp extinguishes in a methane-free atmosphere


16-13%            Dizziness, buzzing noise, rapid pulse, headache, blurred vision


12.1%               Flame safety lamp extinguishes even if methane is present


9%                   May faint or become unconscious


6%                   Movement convulsive, breathing stops,

                        shortly after that the heart stops


·        How To Correct Oxygen Deficiency


The key to keeping an adequate supply of oxygen is ventilation.  In fact, proper ventilation is the best way to deal with hazard: oxygen deficiency, methane concentrations, other hazardous gases, and dust.


·        When Should Oxygen Levels Be Tested in Underground Coal Mines?


Every coal mine operator must make the following tests for oxygen:


·        Pre-shift examination (Act 303(d)(1); COAL/U: 75.303).

·        On-shift examination (Act 303(e); COAL/U: 75.304).

·        Idle and abandoned mines (Act 303(m); COAL/U 75.314).


These tests must be made with a flame safety lamp or any other equipment approved by MSHA.


·        When Should Oxygen Levels Be Tested in Metal and Nonmetal Underground Mines?


Federal regulations require that flame safety lamps or other suitable devices be used to test for acute oxygen deficiency (MNM/U: 57.5-27).  If a main or booster fan in the mine should fail, the air quality must be tested at least within 2 hours of discovering the malfunction, and at least every 4 hours after that (MNM: 57.5-18D(b)(l)).






Methane is formed by the decomposition of organic matter.  It is the most common hazardous gas in the mines, contributing to more than 10,000 miner deaths during the past 60 years.


Methane is found in most underground mines.  Since it is  lighter than air, methane tends to rise to the roof of a mine or tunnel.


Methane injures and kills in two different ways:


·        It asphyxiates (suffocates) you when there is too much of it in the air (by crowding out the oxygen you need to breathe). 


·        It explodes when ignited by a flame or even a spark.


Effects of Excess Methane



Present         Effect


0.25%           No  air with this much methane permitted to be used for ventilation Act 303; COAL/U 75.311, .312


Less than     Normal, safe level



1.0%             Maximum allowed by law, Act 303(h),(i),(1), (t) and (y).  Ventilation must be increased, Act 303(h)(2) and (i).  No electrical equipment permitted to be energized, taken into mine, or operated, Act 303(h).  No intentional roof falls permitted, Act 303(n).  No pillar recovery permitted, Act 303(q).  No shots or blasting permitted, Act 303(s).


1.5%             Highly explosive in air containing coal dust or other explosive gases.  All miners must be withdrawn from area, Act 303(h)(2) and (i)(2).  All electrical power must be shut down, Act 303(h)(2), (i)(2).


5% to 15%    Extremely explosive.


9.5%             Most explosive mixture


Over 15%     Too dense to be explosive


· When Should Methane Tests Be Conducted in Coal Mines?


Numerous mine explosions have occurred because of the failure to test properly for gas.  The law requires mine operators to conduct regular checks of methane concentrations:




                                    When                                              Where                                            By Whom                                Law


PRE-SHIFT         Within 3 hours before               Every working section              Certified person                      Act 303(d)(1); 

                                    each shift, before                         and any other areas                   chosen by operator              COAL/U:

                                    miners enter area                        required by MSHA                                                                            75.303-.303-2


ON-SHIFT           At least once during                   Every working section              Certified person                      Act 303(e),

                                    each coal-producing                                                                              chosen by operator               COAL/U:

                                    shift; more often if                                                                                                                                          75.304-.304-3

                                    necessary for safety


WEEKLY              At least once every                    Return of each air split             Certified person                       Act 303(f),

                                    7 days                                              where it enters main                  chosen by operator                COAL/U

                                                                                                return; pillar falls; seals;                                                                   75.305-.305-2

                                                                                                main return; at least once

                                                                                                entry of each intake and

                                                                                                return aircourse in its

                                                                                                entirety, idle workings;

                                                                                                abandoned areas


ELECTRICAL   At start of each shift                   Every working place                  Qualified persons                     Act 303(h)

EQUIPMENT    during which electrical             where electrical                                                                                    COAL/U

                                    equipment to be used;              equipment used                                                                                     75.307-.307-l

                                    and every 20 minutes

                                    while equipment in operation


AIR SPLIT          Every 4 hours                               Air split returns from                Qualified person                         Act 303(i),

RETURNS            during each shift                          every working                              chosen by operator                  COAL/U



IDLE AND           No longer than 3                          Idle and abandoned                   Certified person;                        Act 303(m),

ABANDONED    hours before anyone                 areas                                                 or anyone who                             COAL/U

AREAS                   enters                                                                                                           normally works there               75.314-.314-l

                                                                                                                                                            and is trained by an


                                                                                                                                                            plan in methane



INTENTIONAL   Immediately before               Around all pillar                          Qualified person                          Act 303(n),

ROOF FALLS         the intentional roof                workings                                         chosen by operator                    COAL/U

                                        fall is made                                                                                                                                                         75.315-.315.1


BLASTING         Immediately before                   All underground areas              Qualified person                           Act 303(s),

                                    firing each shot or                                                                                                                                               COAL/U:

                                    groups of multiple                                                                                                                                               75.320

                                    shots; immediately after

                                    blasting is completed


A “certified person” is anyone certified by the state                                       A “qualified person” is anyone who MSHA finds 

or MSHA to perform methane testing.                                                                   qualified to perform methane testing, and who is

                                                                                                                                                chosen by the mine operator to test.


Gassy Metal and Non-Metal Mines


Seventeen MNM mines have been classified as gassy and are subject to special regulations, found in MNM/U 57.21.  The regs cover fire control, ventilation, illumination, and uses of equipment and explosives.

Some of the regulations affecting the indivi­dual miner are:

· No smoking (MNM/U 57.21-10).

· Methane monitors must be installed on all continuous miners and longwall face equip­ment (MNM/U: 57.21 -80).

· If methane concentrations within 12 inches of the back, face, or rib exceed 1.0%, all equipment must be shut down and work stopped until the gas is diminished (MNM/U 5721-39).

· If methane concentrations go above 1.5%, all miners in the area must be withdrawn (MNM/U 5721-40).

· When welding is done, methane tests must be made just before and continuously through­out the activity (MNM/U 5721-12, 13).

· If the main fan stops at a mine where a single main fan is used, or if all fans stop where multiple main fans are used, ail persons must be withdrawn from the affected part of the mine.  If methane concentrations go above 1%, everyone in the mine must be withdrawn.  If any fan goes off for more than 15 minutes, methane tests must be made (MNM/U 5721-24)).

· Doors must be plainly marked to indicate whether they should be closed or open for ventilation control (MNM/U 57.21-57).

· Preshift examinations of ail working areas must be made within 3 hours before any workers enter the mine (MNM/U 5721-59).




AS OF JANUARY 15, 1980



U.S.  Government

No.  1 Shaft—Horse Draw

Mine I.D.  05-03046

Rio Blanco, Colorado


Rio Blanco Oil Shale

Ca Tract

Mine I.D.  05-03131

Piceance Basin, Colorado


Occidental Oil Shale

Cb Tract

Mine I.D.  05-03140

Piceance Basin, Colorado



Cargill, Inc.

Belle Isle Mine

Mine I.D.  16-00246

Patterson, Louisiana


Domitar Industries

Cote Blanche Mine

Mine I.D.  16-00358

New Iberia, Louisiana


Morion Salt Division

Weeks Island Mine

Mine I.D.  16-00512

New Iberia, Louisiana


Diamond Crystal Salt Co.

Jefferson Island Mine

Mine I.D.  16-00508

New Iberia, Louisiana



Warner Co.

Belle Mine

Mine I.D.  36-00263

Bellefonte, Pennsylvania



Cities Service Co.

Calloway Mine

Mine I.D.  40-00707

Copperhill, Tennessee



Rio Algom Corp.

Lisbon Mine

Mine I.D.  42-00677

LaSal, Utah


DeMar-Boren Contr.

Boren Mines

Mine I.D.  42-01146

Bonanza, Utah


Ziegler Chemical and

Mineral Corp.

Bonanza #8

Mine I.D.  42-01200

Bonanza, Utah



Allied Chemical Corp.

Alchem Trona

Mine I.D.  48-00155

Green River, Wyoming



FMC Mine

Mine I.D.  48-00152

Green River, Wyoming


Stauffer Chemical Co.

Big Island Mine

Mine I.D.  48-00154

Green River, Wyoming


Texas Gulf Inc.

Wyoming Soda Ash

Mine I.D.  48-00639

Granger, Wyoming


Tenneco Oil Co.

Tenneco Soda Ash

Mine I.D.  48-01295

Green River, Wyoming


· What Equipment Is Used To Test For Methane in Coal Mines?


MSHA requires that only methane testing equipment that it has examined and approved be used in the mines (COAL/U: 75.304-3-.315-1).  Several different methane detectors (methanometers) are approved which measure the amount of methane present.


Flame safety lamps until recently were the only device used to measure for methane.


However, they are no longer approved except for used in addition to an approved methane detector (COAL/U: 75.304-3-.315-1).  Flame safety lamps operate on the idea that a naptha flame gets larger the more methane there is in the atmosphere.  But the flame will get smaller if there is too little oxygen and it goes out entirely if the amount of oxygen is less than 16.25%.  The lamp is not exact enough to let you know the precise methane level, especially below 1.25%—which is higher than the 1.0% legal maximum allowable.





    An explosion occurred at approxi­mately 10:00 a.m., July 7, 1977, in the 1 Left Section off “C” Mains of the No.  2 mine, P and P Coal Company, Inc., St.  Charles, Lee County, Virginia.  Three workmen and a foreman who were in the area at the time of the explosion were killed.  MSHA investigations con­cluded that the explosion originated at on near the rubber-tired mine car lo­cated approximately 125 feet outby the face of the No.  2 entry.  An explosive mixture of methane had accumulated because of insufficient ventilation and was ignited by a cigarette lighter that was found at the accident scene.  Forces from the explosion extended through the 1 Left Section and into the 2 Left and 3 Left entries off “C” Mains and dissi­pated near the No.  3 belt drive ap­proximately 3,500 feet from point of ignition.  The explosion forces dis­lodged posts and destroyed stoppings 900 feet outby the face of 1 Left.





    MSHA-approved methane monitors must be installed on: electric face cutting equipment; continuous miners; longwall face equipment; and loading machines.  The monitor should be as close to the working face as possible, and should be set (1) to give an automatic warning whenever the methane level reaches 1.0% (or lower if MSHA says) and (2) to turn off the equipment automatically if the monitor doesn’t work properly or if the methane level reaches 2.0% (or lower if MSHA says).


    The operator must follow a written maintenance program which you can examine.  It must be checked for accuracy at least once a month.


    Sometimes the methane monitors are by-passed by wiring around it so they don’t work.  The monitors may be a nuisance, and they sometimes malfunction, but the risks are so high (even a spark can ignite an explosion) that monitors are worth using and using them well.  Check your methane monitor frequently.





Other gases can trigger explosions and cause health problems.




Gas                             Maximum                 

                                    Allowance                  Where                                                                                    Signs of Its

                                    Concentrations       Found                                     Danger                                  Presence       


Carbon                       0.5%                           Air, soil, coal, rocks               Makes breathing diffi-        Colorless; slight

dioxide                                                                                                            cult; suffocates by                acid taste if

(CO2)                                                                                                              excluding oxygen                 highly concen-

                                                                                                                         from blood                            trated


Carbon                       2.5%                           Produced by fires,                 Limits flow of oxygen           Colorless;

Monoxide                                                      explosions, and heated          to blood; forms                      tasteless;

(CO)                                                               combustibles, and by             flammable gas                       odorless

                                                                       at mine temperatures


Hydrogen                   0.8%                           Produced after fire or          Forms flammable gas          Colorless;

(H2)                                                                explosion                                with air                                  tasteless;



Hydrogen sulfide      0.8%                           Produced after fire or          Very toxic; forms                 Colorless;

(H2S)                                                              explosion; also near             flammable gas with air        smells like                                                                          battery-charging                                                                  rotten eggs



Nitrogen                    None, so long             Air and rocks                         Dilutes oxygen in air,           Colorless;

(N2)                            as it does not                                                             asphyxiant                             tasteless;

                                    displace oxygen                                                                                                         odorless


Nitrogen dioxide       5 ppm                         Produced at high tem-         Toxic; forms corrosive

(NO2)                                                             peratures by diesel              acids in lungs; irritant

                                                                        and gasoline engines,

                                                                        electrical discharges,

                                                                        blasting operations and




·        How Do You Test For And Control Gases in All Mines?




  An MSHA representative must periodically test for the presence of explosive gases other than methane (COAL/U: 75.301-6).  If concen­trations are too high, MSHA must issue a citation to the operator, and the operator must immediately improve ventilation or take other measures to bring the concentration down.  The operator must also take monthly air samples wherever excess concentrations are found (COAL/U: 75.301-7).


If excessive amounts of explosive gases are accidentally released, or if any potential explo­sion hazard exists because of excessive con­centrations, the operator must notify the District MSHA Office and take any steps necessary to reduce concentrations.  The operator must also then take regular air samples (COAL/U: 75.301 -8). 




AFTERDAMP: gas products and smoke pro­duced by fire or methane explosion; including carbonic acid gas, nitrogen, oxygen, carbon monoxide, carbon dioxide, and hydrogen.


BLACKDAMP: mixture of nitrogen (80-90%) and carbon dioxide (10-15%), in oxygen deficient atmosphere, formed after mine fires and methane explosions.


FIREDAMP: combustible mixture of methane, air, and possibly other gases.


WHITE DAMP: Carbon monoxide (CO).


STINK DAMP: Hydrogen sulfide gas (smells like rotten eggs).


MARSH GAS: methane



Gas Emergencies


· sudden changes in ventilation

· blasts of air

· fire alarm systems

 — stench warning

 — visual or sound warnings

· smell of gas

· interruption of normal procedures (fans break down, other miners leave their posts)


·        How Do You Test For And Control Gases in Metal, Non­-Metal, and Sand and Gravel Mines?


Because a variety of gases exist in metal and non-metal mines, the government recognizes certain air concentration safety limits for vari­ous substances.  These are called “Threshold Limit Values” (TLV) (MNM 55/56/ 57.5-1 (a)).


·        Testing For Gases


Mine operators must survey gas, mist, dust, and fumes as often as necessary to determine the adequacy of control measures (MNM: 55/56/ 575-2).  MSHA does not have a set policy for how often these tests should be made, but you should not go for more than a week without a survey.  Where special conditions exist—like changes or breakdowns in the venti­lation system, or a high number of machines being used in one area—the air should be tested more often.


Under some circumstances miners must be withdrawn from the mines when the TLV is reached for some of these substances.  Call your District MSHA Office for the information important to your mine (MNM: 55/56/57.5-1(c)).


Nitrogen dioxide (NO2) and carbon monox­ide (CO) are the two most dangerous and frequently found gases in metal and non-metallic underground mines: They kill quickly, without warning.  N02 is produced by diesel and gasoline engines, welding, and electrical discharges, while CO generally accompanies fires and explosions.  Both gases are generated by blasting.




Carbon Monoxide


CO should be tested for every day in underground mines: Absence of smoke does not mean CO isn’t present.  A smol­dering fire may kill before it ever breaks out into flames, as it did in the Sunshine Mine disaster, taking 91 lives.  Symptoms of CO poisoning are headache, dizziness, and lack of coordination and judgment.  CO poisoning makes strong, healthy peo­ple weak and unable to help others.  If you detect or suspect CO in your mine, put on a self-rescuer or oxygen-generating device and keep a tight seal with your mouth, even if the device heats up uncomfortably.


Hydrogen Sulfide


Hydrogen sulfide, or stink-damp (H2S), is a highly poisonous gas common in both coal and metal/nonmetal mines.  Harmful quantities are often found in gypsum mines, tunnel digging, caissons, and it may be mixed with natural gas.  Hydrogen sulfide is easily absorbed by water, and then released when the water is disturbed.  When H2S is known to exist in a mine, be careful when removing floodwater, and don’t allow water in drainage ditches to move very far.  When you first smell hydrogen sulfide, it stinks like rotten eggs—but the gas also diminishes your sense of smell.  Don’t be fooled into thinking it has disappeared just because you don’t smell it any more.


·        Control Measures


Ventilation must be adequate.  This is the single most effective way of controlling mine gases (MNM: 55/56/57.5-5).


Respirators must be used whenever levels of hazardous particles or gases are high (MNM: 55/56/57.5-5).


After blasting, the blasting area may not be reentered until gases have reached safe levels.  This means the air must be tested after every blast (MNMXU 576- 176).






On May 2, 1972, the worst disaster in the history of hardrock mining took place at the Sunshine silver mine in Kellogg, Idaho.  An underground fire caused 91 men to perish from carbon monoxide poisoning and suffocation.  The lack of safety precautions and proper equipment contributed heavily to the high death toll.  The following account of the disaster was excerpted from the report of the Bureau of Mines investigation.



May 2, 1972




Smoke was detected in the main haulageway near the electric shop on the 3700 level of the Sunshine Mine, Kellogg, Idaho, about 11:40 a.m., May 2, 1972.  The volume of smoke, accom­panied by carbon monoxide, in­creased rapidly and was also detected in the 3100 level main haulageway.  Both the 3100 level and 3700 level haulage drifts served as main fresh air intakes to the stope area below 3700 level near the No.  10 shaft, where most of the 173 men in the mine that shift were assigned.  Mine supervisors, after attempting to locate the tire, ordered evacuation of workmen from the mine about 12:03 p.m.  Before the evacua­tion was halted by the death of the No.  10 shaft hoistman, 80 men escaped from the mine.  An intensive rescue operation, organized by industry and Bureau of Mines personnel resulted in the rescue of 2 men.  The remaining 91 men died of carbon monoxide poison­ing.  None of the survivors reported seeing fire or flames.  The Bureau of Mines believes the probable cause of the fire was spontaneous combustion of refuse near scrap timber used to backfill worked out stopes.


Why Did The

Sunshine Mine

Disaster Happen?


The Bureau of Mines believes the follow­ing factors contributed to the severity of the disaster:


1.     Ineffectiveness of stench warning sys­tem.

2.     Delay in beginning mine evacuation.

3.     Ineffectiveness of the mine communi­cation system.

4.     Inadequacy of the emergency escape­way system.

5.     Inadequacy of the emergency fire plan.

6.     Use of a series ventilation system.

7.     Failure to seal abandoned areas of the mine.

8.     Failure to monitor the mine atmo­sphere.

9.     Failure to construct incombustible ven­tilation bulkheads.

10.   Lack of remote controls on major underground fans.

11.   Failure to maintain self rescuers in useable condition.

12.   Failure to train underground em­ployees in use of self rescuers.

13.   Failure to conduct mine survival training.

14.   Failure to designate anyone as being in charge of the entire operation in the absence of top mine officials.


The worst disaster in the history of hardrock mining was needless.  The cause was not any inherent flaw in the Sunshine Mine, but lax and negligent safety practices.  Miners died be­cause self-rescuers had been allowed to cor­rode over the years; because they did not know how to use them; because they had no idea how to cape with poisonous gases or escape safely from their own mine.  Had a simple carbon monoxide test been made, the fire could have been discovered much earlier and the men might have escaped safely—if they had been properly trained.


The shack of this senseless tragedy spurred Congress to pass more stringent regulations for metal and nonmetallic mines with the Federal Mine Safety and Health Amendments of 1977.  Many of the lessons learned at the Sunshine disaster are now incorporated in federal regu­lations for metal and non-metallic mines (MNM: 55/56/57).  Other lessons still have not be­came law, and are only valuable as long as miners are vigilant.


Lessons of the Sunshine Mine Disaster


·        Every mine should have multiple escape­ways and an evacuation plan, and miners should be trained for emergencies (MNM 55/56/57.11, .18).


·        Underground mines should be tested daily for carbon monoxide.  [Current regula­tions only require air quality monitoring “as often as necessary”] (MNM/U: 55/56/57.5-.2).


·        Self-generating oxygen devices should be provided in all underground mines.  (This will soon be required in coal mines, but as yet no regulation exists for metal and nonmetallic mines.)


·        Self-rescuers should be inspected and maintained, and every miner should be trained to use them (MNM/U: 57.15-30, .18).


·        Scrap timber and other combustible waste materials should be removed immediately from the mine.  (MNM: 55/56/57.4-12, .13 require containment or removal of flammable wastes.)


·        Series ventilation systems should not be used, because they tend to spread toxic gases through the mine.  (There is no prohibition against series ventilation.)


MSHA Standards


    We think the exposure standards set by MSHA are so complicated that they are almost impossible for the person on the job to use.  We put them in this book (on pages 170-171) to alert you to the levels of gases which may be dangerous in your mine.  And if you want to study the chart, you can learn much about gases.  But principally we have tried to explain the standards and how they work in the hope that this will help you to work more closely with your inspector to monitor the conditions and enforce the regulations.  We have also included the standards recommended by the National Institute for Occupational Health and Safety (NIOSH), which in most cases are much more protective of your health than MSHA’s stan­dard: Work with your union representative to force MSHA to adopt these stricter standards, or to get the company to accept these levels.


    MSHA has different standards for gas levels.  They are:


    Threshold Limit Value (TLV).  The “weighted average” of gas exposures over a full 8-hour shift may not go above the TLV.  This number doesn’t help you very much, because your exposure may exceed the TLV as long as it averages out below the TLV at the end of the day.  If gas levels remain near the TLV for very long, say two hours for a couple of days, call the inspector.


    Short Term Exposure Limit.  This number tells you how much gas you can be exposed to for very short periods of time.  If an air quality test shows gas levels anywhere near this n umber, you are probably in danger.  Call the inspector.


    Imminent Danger Level.  If gas levels get this high, the mine must be evacuated.


    Ceiling.  Some gases don’t have TLV’s or short term exposure levels.  The rule is that no person may be exposed to gases above the ceiling levels.


    We know you don’t have the testing instruments to take the test yourselves.  You can call MSHA or NIOSH to make the test.  We recom­mend that you have the test taken every six months.