Damps is the collective name given to all gases other than air found in coal mines in Great Britain. The term corresponds to the Middle Low German dampf, meaning “vapour”.
Normal atmospheric air consists mainly of nitrogen, oxygen and carbon dioxide in the proportions 79%, 20% and 0.03%.[a] The air down mines however, can contain varying amounts of pollutants – chiefly carbon dioxide (CO2) and methane (CH4) released as a result of mining operations, known as blackdamp and firedamp respectively. Other pollutants can include carbon monoxide (CO), sometimes called whitedamp, and hydrogen sulphide (H2S), stinkdamp.
Canaries were used in mines to warn of noxious gases from 1911 until 1986, when they were replaced by electronic detectors. The birds were chosen because canaries are particularly sensitive to carbon monoxide; any sign of distress from the birds meant that the air was unsafe and that miners should evacuate the area. Mice were sometimes employed in the same way.
Afterdamp is air that contains a high concentration of carbon monoxide, typically formed in a mine in the aftermath of an explosion of gas and dust. Carbon monoxide is colourless and odourless, and kills by binding to the haemoglobin in red blood cells, impairing their ability to transport oxygen around the body.
Eighty-nine miners were killed at the Ince Hall Colliery’s Arley mine in 1854 following an explosion caused by firedamp in which thirty-seven miners died; the rest were suffocated by the resulting afterdamp. In 1992 a case was published in the BMJ of a woman who had bought a house on land over an abandoned coal mine, which she claimed was making her feel nauseous and dizzy. Neighbours also reported having difficulty in lighting gas appliances, all of which was traced to carbon dioxide leaking into their houses from the mine.
Blackdamp, also known as stythe or chokedamp, is a gas containing elevated levels of carbon dioxide and correspondingly lowered levels of oxygen. Once coal is exposed in a mine it begins to oxidise, even at low temperatures, producing carbon dioxide. That may result in the air containing about 5% of the gas, more than 800 times the level of CO2 in the above-ground atmosphere; at higher temperatures the concentration may be as much as 10–12%. If the CO2 is produced from rotting timber, it can constitute up to 20% of the air in a mine.
As the oxygen level in the air decreases, miners might begin to experience difficulty in breathing, but death can occur very quickly after the onset of symptoms. The flames of modern safety lamps are designed to extinguish when the oxygen concentration falls to 18%, giving miners sufficient warning to escape. Blackdamp can also be a danger in sewers and wells.
In 1862, at the Hester Pit in Northumberland, 204 men and boys lost their lives to blackdamp. In 1992 a case was reported in the British Medical Journal of a woman who had bought a house built on land over an abandoned coal mine, which she said made her feel nauseous and dizzy. Neighbours also reported difficulty in lighting their gas appliances, all attributed to a leakage of carbon dioxide from the mine below into their homes.
Formerly known as fulminating damp, firedamp is the name given to flammable gases found in coal mines, especially methane, which are encountered particularly in areas where the coal is bituminous. The gas accumulates in pockets in the coal and adjacent strata, which when penetrated can trigger explosions. Historically, if such a pocket was highly pressurised, it was termed a “bag of foulness”.
Firedamp became more problematic as pits and workings got deeper. In 1751 firedamp was described as “fiery air” in the cannel pits at Haigh near Wigan. When the gas was detected, a candle was lowered into the pit to explode it. The first firemen, covered by sackcloth soaked in water, crawled into the area where gas was present on his belly holding a long pole with a candle attached to explode the firedamp before the miners began their shift. They were sometimes called the “penitent” from their ragged appearance. Accounts show that the Bradshaighs paid compensation for injuries caused by the “fiery damp”.
The first mining accident on record, in 1621 at Gateshead, was caused by an explosion of firedamp, resulting in the death of one miner. In 1705 Gateshead was also the scene of the first major disaster attributed to firedamp, in which thirty miners were killed.
- Argon and other inert gases make up the remainder