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.
WHAT'S IN THIS CHAPTER:
1. MAJOR AIR AND GAS DANGERS UNDERGROUND
2. OXYGEN DEFICIENCY
3. METHANE GAS
4. OTHER HAZARDOUS GASES
MAJOR AIR AND GAS DANGERS UNDERGROUND
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.
SOME GENERAL PRECAUTIONS
· 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
(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
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:
METHANE TESTING REQUIRED BY LAW IN UNDERGROUND COAL MINES
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;
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).
ACTIVE “GASSY” METAL,
AS OF JANUARY 15, 1980
No. 1 Shaft—Horse Draw
Mine I.D. 05-03046
Rio Blanco, Colorado
Rio Blanco Oil Shale
Mine I.D. 05-03131
Piceance Basin, Colorado
Occidental Oil Shale
Mine I.D. 05-03140
Piceance Basin, Colorado
Belle Isle Mine
Mine I.D. 16-00246
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
Mine I.D. 36-00263
Cities Service Co.
Mine I.D. 40-00707
Rio Algom Corp.
Mine I.D. 42-00677
Mine I.D. 42-01146
Ziegler Chemical and
Mine I.D. 42-01200
Allied Chemical Corp.
Mine I.D. 48-00155
Green River, Wyoming
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
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 HAZARDOUS GASES IN ALL MINES
Other gases can trigger explosions and cause health problems.
DANGEROUS MINE GASES FREQUENTLY FOUND
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,
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).
· 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.
· 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).
THE SUNSHINE MINE DISASTER
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.
SUNSHINE MINE DISASTER,
May 2, 1972
BUREAU OF MINES FATAL
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
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.)
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.