Gases

The most important, naturally occurring, potentially hazardous gases in coal mines are methane and hydrogen sulfide; oxygen deficiency can occur when either is present.

Methane is a colorless, odorless, flammable gas. It is not toxic; however, it is highly flammable and may form explosive mixtures with air. High concentrations of the gas in closed spaces may reduce the oxygen percentage in air and cause suffocation. Throughout the history of coal mining, methane explosions have been frequent in coal mines and have been the cause of many mine disasters.

Hydrogen sulfide is another colorless, highly toxic, and flammable gas. It is heavier than air and tends to accumulate at the bottom of poorly ventilated spaces. It smells like rotten eggs, but it quickly deadens a person's sense of smell, so that potential victims may be unaware of its presence until it is too late. Prolonged exposures at lower levels can lead to bronchitis, pneumonia, migraine headaches, pulmonary edema, and loss of motor coordination. High exposures at 50 to 200 parts per million (ppm) can lead to convulsions, coma, and death.

To learn more about MSHA Part 48 training requirements visit our MSHA Part 48 Subpart B Surface Mining Online Training web page.