Dampf

22nd October was the 140th anniversary of The Blantyre Mine Disaster of 1877; Scotland's worst mining accident it terms of body-count N=207. Nobody likes to record the monetary cost in the Guinness Book of Underground Accidents although it often looks like this was all that mattered to the management and proprietors. In May 1878 the Blantyre management William Dixon & Co. Ltd., for example, evicted 34 widows who were awkwardly occupying tied cottages but not longer had husbands working down the pit on account of being killed there the previous year.

We don't do coal any more, or at least we recognise that we shouldn't because burning coal is a terrible thing for the atmosphere and global warming. But in the 18th and 19th and indeed 20th centuries, coal was king driving forward the industrial revolution which made everyone richer and some fabulously wealthy. I've alluded to the story that my Great Aunt Lily lived in retirement in Buddleigh Salterton, Devon. The name of their home, Woolsington, was the same as location of Newcastle Airport because her husband (or maybe 'husband' because it was hard to find a marriage cert) Walter Bell was a descendant of Northumberland coal barons who lived in Woolsington Hall. Lily had that peculiar mix of thrift and extravagance that goes with not having to worry about money.

This is all a bit of a ramble to explain why I'm on about noxious gases today: because 'chokedamp' appeared in the post-mortem on the 1877 Blantyre explosion and I'd never seen the word before. Firedamp, yes: that's methane. *damp apparently comes from the [same root as] the German word Dampf = steam or vapour and there are at least four variations. It's interesting because coal isn't coal but a wide variety of combustible materials of widely different colour, hardness and calorific value. Welsh steam coal was a high quality, hard anthracite [prev] that was exported all over the World from Cardiff docks because it burned clean and hot and was ideal for powering ships.  The Brits set up coal bunkering depots at convenient places round the globe to act as filling stations. Mindelo in Cabo Verde is one example. The local geology - not only the coal measures but the over-burden and under-burden - would dictate the atmospheric conditions down each pit. Miners and managers both would have a vested interest in knowing about the local conditions and acting defensively.

The solution to most *damp probbies was to increase ventilation and many ingenious schemes were invented to a) get fresh(ish) air down to where the workers were and b) pump out the water which inevitably accumulated at the bottom of the workings. In Blantyre and elsewhere they just lit a big fire at the bottom of one shaft to drive an updraft which would suck air /oxygen in down another shaft. Coal at the pithead is cheap and it seems like a rather clever appropriate-tech solution - fans being so expensive and how would you drive them?  The Enquiry exposed the fact that up draft was being serviced from No.2 shaft which was in turn getting its 'air' from No.3 shaft. Along that enormous distance more *damp was percolating into the spaces than was being diluted by the outside fresh air. It just takes one miner to decide it was time to light his pipe, and WHOOOOMPH! That sounds like victim blaming but such data appeared often enough in the reports of explosions.

ANNyway [stop me if I'm boring you] . . . the chemistry

• Firedamp, that's mainly methane CH₄ which is basically the same as North Sea Gas which is being piped ashore by UK and Norway. In other words highly flammable if mixed with oxygen . . . and triggered by a spark or a naked flame. Humphrey Davy's safety lamp used a steel gauze to separate the naked flame, which enabled miners to see to work, from the flammable mixture that surrounded them. Once the methane ignited the flame front travelled fast along the shafts, fuelled by coal-dsut and more methane in a catastrophic deflagration. Note: not a detonation because it travelled slower than the speed of sound - but far faster than a man, pit-pony or canary could run. And of course, if you survived the actually blast of flame you were done for aNNyway because there was no oxygen left.
• Afterdamp is what they call this deadly residuum. It is rich in CO carbon monoxide which forms a strong essentially irreversible bond with haemoglobin, so even if you're breathing when they get you hospital you are like to die. Afterdamp will also have varying amounts of CO₂ carbon dioxide, which will kill you too but will flee haemoglobin if oxygen is supplied. I've mentioned a near-death experience in the lab initiated  by culpably foolish storage of dry-ice = solid CO₂. In terms of volume afterdamp will be mainly nitrogen N₂ because air is 80% inert N₂ which doesn't take part in any of the chemical conversions . . . except in the red-hot chambers of internal combustion engines where it is converted the atmosphere destroying NO_x compounds
• Whitedamp is also a mixture of carbon monoxide maybe with a dash of H₂S, hydrogen sulphide. The canaries, which were instituted following experiments by Professor John Scott Haldane, were designed to faint dead away if exposed to levels afterdamp or whitedamp that weren't enough to kill a man. That Haldane is the father of JBS Haldane the geneticist.
• Chokedamp, stythe or blackdamp was more of an asphyxiant than a poison. The atmosphere was depleted of life-sustaining oxygen leaving only N₂ and CO₂ and water-vapour behind. You died aNNyway.
• Stinkdamp is when the air is particularly rich in H₂S, hydrogen sulphide reeking of rotten eggs and old farts. H₂S, like CO is toxic as well as smelly.