: high-pitched cough ... I think I'm getting the Black Lung, Pop. It's not very well ventilated down there.
: For Christ's sake, Derek, you've been down there one day. Talk to me in thirty years.
Relieving the earth of its minerals hasn't always been the glamorous, exciting occupation we know it as today. Whereas logging now ranks as one of the most dangerous jobs to have, mining is historically known for cave-ins and lethal, invisible assassins. No, I'm not referring to ninjas but instead, gas. It is fairly well-known that carbon monoxide is a colorless, odorless and deadly gas; a fact given to the masses by TV when attempted suicides cruise their garages in idling cars. But CO is only one of the ninjas, er, gases that can kill coalminers dead. Explosions were a danger in addition to asphyxiation or being crushed by a mountain. What was a coal miner to do before the advent of gas-detecting technologies of which I have almost no knowledge?
Enter the canary. This little guy was Flintstones technology at its best. Fortunately he couldn't talk and complain about a job that is comparable to being a medieval king's food-taster. A canary was used to test for the presence of noxious fumes primarily because of its sensitivity, but also because of its tendency to physically react to the gases before it knocked off.1 "Canaries were preferred over mice to alert coal miners to the presence of carbon monoxide underground.... For instance, when consumed by the effects of carbon monoxide, a canary would sway noticeably on his perch before falling."2
Today, 'canary in a coal mine' is an idiom used to describe something that gives a warning, usually to its own detriment, of impending danger. A small market's demise indicating a large drop in the global market is one example.
The Gas Ninjas3
A mixture of methane and other flammable gases that is explosive at concentrations between 4% and 16%. Largely present in bituminous areas, bitumen being a sticky, black mixture of organic liquids. The term damp used in these names is believed to derive from the German word, dampf, meaning vapor.
A mixture of nitrogen and carbon monoxide dangerous when there is little oxygen. Sometimes referred to as stythedamp or chokedamp.
A mixture of carbon monoxide and hydrogen sulphide resultant from coal-combustion.
Hydrogen sulfide gives off the odor of rotten eggs or flatulence, and thus is not as sneaky as the other ninjas on the list. No canary necessary for its detection.
2 Mine Safety Health Administration Website - www.msha.gov
If one is interested in further safety prevention methods of historical coal mining, read up on the Davy Lamp, Geordie Lamp, and also The Fireman in the Coal Mines. Feel free to create a writeup if none exist.