Afterdamp is the residual gas mixture that fills underground workings immediately after a firedamp or coal dust explosion. It consists primarily of carbon monoxide, carbon dioxide, and nitrogen, completely displacing breathable oxygen. The extreme toxicity of the carbon monoxide in this mixture is responsible for killing miners who survive the initial blast and thermal shock of the explosion.
Heard on the job
Rescue teams can't enter the lower panel until the ventilation fans clear the afterdamp.