|Carbon Dioxide (CO2)
A true gas formed by the oxidation of carbon, occurring in exhaled air, in the products of decomposition of some types of explosives, and in the products of combustion of all carbonaceous matter. It is also formed by the action of acid water on limestone, and by the slow oxidation of coal.
It is heavier than air, is slightly soluble in water, and at temperatures below 3l.5C can be liquified by pressure. It is a respiratory stimulant up to l0% when it becomes a narcotic poison. At 26% it is an inhibitor of life and fire, a property made use of in some types of fire extinguishers. It solidifies at -80C.
The coal mines act of 1911 limits the CO2 permissible in mine air to l.25%, which may appear very low, but its effects on respiration must be considered together with those of a reduced oxygen content. Its presence is detected in mines by the effect of reduced oxygen on the luminosity of the flame of a flame safety lamp. Its absolute determination is made by laboratory analysis of a mine air sample.