Six miners and mine rescue workers have been declared dead and several more are missing following a series of methane explosions at two coal mines in southern Poland this week. The first explosion occurred at the Pniowek Mine in Upper Silesia Province early on the morning of Wednesday 20 April 2022, trapping a number of miners over 1000 m below the surface. Rescue workers who entered the mine to try to reach the trapped workers were caught by a series of further explosions, which killed at least one rescue worker and three miners, with another six miners seriously injured and seven more still trapped within the mine. The following day another rescue team was hit by two further explosions, injuring ten, some of them seriously. Rescue attempts were suspended on Friday 22 April due to the danger of further explosions, despite miners still being trapped within the mine.
On Saturday 23 April an Earthquake triggered a release of methane at the Borynia-Zofiowka Mine, also in Upper Silesia, triggering a series of explosions and trapping ten miners below ground. Four of these miners have now been located by rescue workers, one of whom has been declared dead. No statement has been made about the health of the other three rescued miners, and another six are still missing.
Coal is formed when buried organic material, principally wood, in heated and pressurised, forcing off hydrogen and oxygen (i.e. water) and leaving more-or-less pure carbon. Methane is formed by the decay of organic material within the coal. There is typically little pore-space within coal, but the methane can be trapped in a liquid form under pressure. Some countries have started to extract this gas as a fuel in its own right. When this pressure is released suddenly, as by mining activity, then the methane turns back to a gas, expanding rapidly causing, an explosion. This is a bit like the pressure being released on a carbonated drink; the term 'explosion' does not necessarily imply fire in this context, although as methane is flammable this is quite likely.
Fire is much feared in coal mines due to this combination of flammable gas and solids, with methane and coal dust both potentially explosive when they come into contact with naked flames. To make matters worse, the limited oxygen supply in mines often means that such fires will involve incomplete combustion, in which all the oxygen is used up, but instead of forming carbon dioxide forms the much more deadly carbon dioxide, with potentially lethal consequences for anyone in the mine.
Coal is also comprised more or less of pure carbon, and therefore reacts
freely with oxygen (particularly when in dust form), to create carbon
dioxide and (more-deadly) carbon monoxide, while at the same time
depleting the supply of oxygen. This means that subterranean coal mines
need good ventilation systems, and that fatalities can occur if these
break down.
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