Incomplete combustion of coal releases many poisonous gases like carbon monoxide in the environment. This carbon monoxide gas is fatal to health, can lead to coma and even death of the persons sleeping in that room.

In a closed room supply of oxygen is limited. When coal burns in limited supply of oxygen, carbon monoxide (CO) is produced instead of carbon dioxide (CO2).

Carbon monoxide is very poisonous gas which when inhaled leads to person’s death as it lowers the levels of oxygen in blood.