Roger Jones age 14, of Gadsden, Ala., for his question:

WHAT IS FIREDAMP?

Damp is a dangerous gas found in mines. It is most often found in coal mines, where it is a hazard to miners. Firedamp is the most common kind of damp. It is chiefly methane, a tasteless, ordorless gas.

Firedamp forms when decaying plant matter produces coal. It istrapped in seams or cracks in the rock. When miners cut into the seams or cracks, the gas is released.

Firedamp burns readily and can explode when mixed with air in certain proportions. Exploded firedamp leaves afterdamp, a deadly gas that contains poisonous carbon monoxide and nonpoisonous nitrogen and carbon dioxide.

Chokedamp and blackdamp are common names for carbon dioxide, a gas that is denser than air. This gas gathers at the bottom of pits and low places in mines, where it reduces the amount of oxygen in the air. If too much carbon dioxide is present, miners will suffocate.

Miners once carried canaries into the mines to test for gases. They knew gas was present if the birds collapsed. Today, various mechanical, chemical and electrical devices are used to test for the presence of gases.