ISSUE DATE: 4/01/2011 

PROGRAM INFORMATION BULLETIN NO. P11-18 

FROM: KEVIN G. STRICKLIN

 Administrator for 

 Coal Mine Safety and Health 

 LINDA F. ZEILER

 Acting Director of Technical Support 

SUBJECT: Reissue of P07-05 - The Danger of Oxygen Deficiency in 

 Underground Coal Mines 

Who needs this information?

This Program Information Bulletin (PIB) applies to underground coal mine operators 

and Mine Safety and Health Administration (MSHA) personnel. 

What is the purpose of this bulletin?

The purpose of this PIB is to increase awareness of the detrimental effects associated 

with low oxygen concentrations, emphasize the importance of testing for oxygen 

concentrations at certain locations, and identify some of these locations in underground 

coal mines. 

Information

Methane liberation in the absence of effective ventilation can present serious hazards to 

miners. In addition to being an explosive gas, an accumulation of methane in high 

concentrations can result in a mine atmosphere that is deficient in oxygen. 

Atmospheres with oxygen concentrations below 19.5 percent can have adverse 

physiological effects, and atmospheres with less than 16 percent oxygen can become life 

threatening. 
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Methane may be released from a variety of sources in a mine, including strata in the 

roof or floor, as well as the coal seam itself. Since methane continues to be released after 

mining is completed, effective ventilation or sealing of mined-out areas is critical. 

Consequently, to verify that ventilation is effective and seals are maintained, weekly 

examinations by mine operators, as well as other examinations and surveys by MSHA 

personnel are required. To avoid exposing themselves to hazardous situations, each 

person making these examinations should have a thorough understanding of how the 

ventilation system is intended to function and how and where low levels of oxygen may 

exist; and they should be able to recognize situations conducive to accumulation of 

methane or other contaminant gases. Some of the more likely areas where oxygendeficient atmospheres may be encountered are bleeder entries, worked-out areas, 

approaches to seals, low airflow areas, and areas ventilated by air currents with high 

levels of methane emanating from caved areas of a gob. 

Methane is lighter than air and tends to migrate upwards. Methane may accumulate 

when the ventilation system is not moving air with sufficient velocity to mix with the 

methane, or the air is not reaching into cavities or other high locations, such as those 

created by roof falls. At times, methane accumulations may reach concentrations high 

enough to displace oxygen and create an irrespirable atmosphere that is immediately 

life threatening. 

A fatal accident occurred when two foremen were making examinations in a bleeder 

system. As the two were traveling over fallen rock and into the roof fall cavity area, 

which had been supported after the fall, they encountered a methane-rich oxygendeficient atmosphere. Both foremen immediately lost consciousness and collapsed. 

One foreman apparently fell to an area with a higher oxygen level near the mine floor 

where the ventilation air stream existed. He regained consciousness and traveled outby 

to seek help. The other died due to lack of oxygen. 

Miners and MSHA personnel should understand the cause of this tragic accident and be 

aware that the harmful effects of entering an oxygen-deficient atmosphere can be so 

immediate that it is impossible to retreat to safety. Miners, and especially examiners, 

should exercise caution wherever high methane concentrations are suspected, 

particularly when entering or examining roof cavities. Miners and MSHA personnel 

should also fully understand the operation of multiple gas detection devices and the 

significance of their visual and audible alarms. Areas where alarms are activated 

should be approached slowly to permit adequate time for gas detection devices to react. 

High levels of methane or other contaminant gases should be a warning that the oxygen 

level may be lower than normal. 
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What is the background for this PIB?

Oxygen is depleted from the atmosphere by oxidation of coal, wood, or other organic 

materials. Oxygen deficiency can also occur as contaminant gases liberated from the 

coal strata displace the oxygen. Atmospheres with oxygen concentrations below 19.5 

percent can have adverse physiological effects. The following are the likely effects of 

depressed oxygen levels in air: 

Percent Oxygen in Air Effect

 17 Faster, deep breathing 

 15 Dizziness, buzzing in ears, rapid heartbeat 

 13 May lose consciousness with prolonged 

 exposure 

 9 Fainting, unconsciousness 

 7 Life endangered 

 6 Convulsive movements, death 

Historically, emphasis has been placed on testing for oxygen near mine floors and in 

low areas to detect gases that are heavier than air, such as carbon dioxide. However, 

gases that are lighter than air, such as methane, tend to migrate upward; and oxygendeficient atmosphere may be found near the roof or other high spots. For example, 

methane seeping from feeders in cavities such as those created by roof falls will migrate 

upward, displace the air, and create an oxygen-deficient atmosphere if ventilation is 

ineffective. Similarly, methane that is layered near the roof or high areas can migrate 

updip for a considerable distance, even against air currents, and accumulate in these 

areas. These situations, however, can be prevented with ventilation that causes the air 

to move with a velocity sufficient to mix with the methane or other gases and render 

harmless atmosphere. 

Typically, multiple gas detection devices give visual and audible warning signals when 

a predetermined gas concentration is encountered. Users of these devices should be 

familiar with their operation and should realize that there is a delay between the time 

the gas is encountered and the device responds. This delay period varies with the type, 

age, and condition of the device. It should be noted that when multiple gas 

concentrations are encountered, an alarm will sound when one of them reaches the 

predetermined concentration that activates the alarm. If a second gas reaches its 

predetermined level, the alarm may continue to sound and an additional visual 

warning signal will be activated. For example, a visual and audible signal may activate 

when methane concentration in excess of 2.0 percent is detected; then, if an oxygen 

concentration of less than 19.5 percent is detected simultaneously, another visual 

warning will activate and the audible alarm may remain unchanged. 
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What is MSHA’s authority for this PIB?

The Federal Mine Safety and Health Act of 1977, as amended, 30 U.S.C. § 801 et seq.; 

30 C.F.R. §§ 75.321(a) and 323. 

Is this PIB on the Internet?

This PIB may be viewed on the World Wide Web by accessing the MSHA home page 

(www.msha.gov ) and choosing “Compliance Info” and “Program Information 

Bulletins.” 

Who are the MSHA contact persons for this PIB?

Coal Mine Safety and Health, Safety Division 

Michael G. Kalich, (202) 693-9714 

E-mail: kalich.michael@dol.gov

Pittsburgh Safety and Health Technology Center, Ventilation Division 

Dennis A. Beiter, (304) 547-2320 

E-mail: beiter.dennis@dol.gov

Who will receive this PIB?

Program Policy Manual Holders 

Underground Coal Mine Operators 

MSHA Special Interest Groups