Thanks Vic and HPW. We are so lucky here to have access to all your mining knowledge! As for the bean-can, I am delighted to have now found out what it is. I've only ever seen it on pictures but in my naivety I've always thought it was some kind of bait-box! Which brings me to another question: Where do miners keep, and eat, their 'bait' when underground? Surely, you can't have a 'canteen' underground.
Another thing that was interesting to read was how the bean-can worked - by converting carbon monoxide to carbon dioxide. Many people think that carbon dioxide is dangerous, but back in the 70's when barbiturate drugs were dished out like Dolly Mixtures (remember them?), for insomnia, respiratory difficulties caused by overdosing were treated with carbon dioxide. - not oxygen as - carbon dioxide is what stimulates the repiratory centre in the brain.