Afterdamp

The toxic mixture of gases — chiefly carbon monoxide, alongside carbon dioxide and nitrogen — left behind in a mine after an explosion or fire, distinct from firedamp (the methane that often causes the explosion in the first place).

Historical usage

The term is most associated with coal mining, where a firedamp (methane) explosion, sometimes followed by a much larger secondary coal-dust explosion, left afterdamp behind in the workings — but the same carbon-monoxide poisoning mechanism can follow any mine fire, whatever the ore being worked.

How it worked

The carbon monoxide in afterdamp is what actually kills: it binds to haemoglobin in the blood far more readily than oxygen does, starving the body of oxygen even at concentrations too low to see or smell. This is exactly the mechanism recorded in several of this site's own disaster records, including the 1952 Greenside Mine fire.

Why it was used

Recognising afterdamp as a distinct, separate danger from firedamp mattered because it meant a mine could remain lethal even once any flames or explosion were over and the immediate fire risk had passed — rescuers and returning miners faced a second, invisible hazard in air that could look and smell clear.

Risks & limitations

Afterdamp is essentially undetectable by human senses alone, which is why canaries — far more sensitive to carbon monoxide than people — were introduced into British collieries in the 1890s at the urging of physiologist John Scott Haldane, and remained in use as a living gas detector well into the 20th century.

Regional variation

"Damp" is a generic historical term for a dangerous mine atmosphere (from the German Dampf, vapour), giving a family of related terms — firedamp (methane), blackdamp/chokedamp (oxygen-deficient, carbon dioxide-rich air) and whitedamp (carbon monoxide specifically) — of which afterdamp, the mixture left after an explosion or fire, is one.

Disasters associated with this term

Included only where MineArchive's own research gives a reasonable evidential basis, with the nature of the relationship stated — not every disaster where this term might plausibly apply.

• Magpie Mine suffocation of three Maypitt miners (direct cause)
  Fires deliberately lit underground during a dispute over the Great Redsoil vein produced toxic smoke that suffocated three miners from the neighbouring Maypitt mine — the same post-fire gas hazard afterdamp describes, from an arson fire rather than an explosion.
• Snaefell Mine disaster (direct cause)
  Smouldering support timbers filled the workings with carbon monoxide; investigator Dr Haldane — later responsible for introducing mine-rescue canaries against exactly this gas — examined the disaster and measured how quickly it could disable a person.
• Greenside Mine fire, 1952 (direct cause)
  Four miners were killed by carbon monoxide gas released when a fire in timbering fanned into life; textbook afterdamp poisoning following a mine fire rather than an explosion.

Sources

1. (secondary) Afterdamp — Wikipedia

Record created: 20 August 2026 · Last researched: 20 August 2026