There were many ways to die in the coal mines. Health problems included debilitating diseases like pneumoconiosis and emphysema caused by the dusty conditions. As well as facing the risks of rock falls, flooding and being mangled by powerful machinery, the men working in many deep mines, and particularly those in Wales, were at risk from the release and possibly disastrous explosion of a gas commonly known as ‘coal damp’ (methane). By the end of the 19th century this was reasonably well understood as the cause of underground explosions, and had led to the development of Sir Humphrey Davy’s safety lamp and the well-known practice of taking canaries down to the coal face. The birds were found to be much more sensitive than men to changes in the atmosphere during mining resulting from the release of the gas entrained in the rock, and there is no doubt that the birds saved many lives by giving early warning. Later, they would be replaced by gas-sensitive monitoring equipment, and improved powerful mechanical ventilation would drain the methane away, keeping the gas well below its explosive limits.