blackdamp is encountered in enclosed environments such as mines, sewers, wells, tunnels and ships' holds. it occurs with particular frequency in abandoned or poorly ventilated coal mines. coal, once exposed to the air of a mine, naturally begins absorbing oxygen and exuding carbon dioxide and water vapor. the amount of blackdamp exuded by a mine varies based on a number of factors, including the temperature (coal releases more carbon dioxide in the warmer months), the amount of exposed coal, and the type of coal, although all mines with exposed coal produce gas.