Carbon Monoxide in Atmosphere

Carbon Monoxide is scarcely a normal constituent of fresh air, although it occurs in the minutest traces in the air of towns and of volcanic districts. It also occurs in railway tunnels and even in well-ventilated coal mines to the extent of 0.002 to 0.004 per cent. It is a most dangerous gas, 0.43 per cent, being fatal to man in a short time. Even 0.2 per cent, may prove fatal if breathed for a long time. Headaches and other unpleasant symptoms are produced by concentrations ranging from 0.03 upwards.

Carbon monoxide is produced by the incomplete combustion of fuel, and since it readily diffuses through heated iron, it frequently happens that iron stoves, used for heating purposes in large buildings, constitute a source of this gas in the air, the carbon monoxide diffusing into the building, instead of being carried up the chimney or burned.

Ordinary coal-gas may contain anything up to 20 per cent, of carbon monoxide, and an escape of coal-gas into the air produces a proportionate vitiation of the same.