Which gases must be detectable by personal gas detectors issued to workers?

• A. Methane, Oxygen, Carbon Monoxide
• B. Methane and Hydrogen Sulfide
• C. Oxygen and Nitrogen
• D. Nitrogen and Argon

Answer: (A)

In underground coal mining, personal gas detectors are focused on the three atmospheric hazards that pose the most immediate risk to a worker: a flammable gas, oxygen level in the air, and a toxic gas. Methane is the primary flammable gas found in coal seams, so detecting it helps prevent explosions. Oxygen must be monitored to ensure there is enough breathable air and to catch any dangerous shifts in the atmosphere. Carbon monoxide is a toxic gas that can accumulate from ventilation problems or combustion processes, so detecting it is crucial for worker safety. Together, these three gases cover the main explosion risk, breathing-air safety, and toxic exposure concerns that a miner could encounter.

Inert gases like nitrogen or argon aren’t a direct toxic or flammable risk in the same way for routine detection, and hydrogen sulfide, while hazardous, isn’t part of the standard minimum detector set in all regulations. Therefore, the combination that includes methane, oxygen, and carbon monoxide meets the essential protective purpose of personal gas detectors, making it the best choice.