Tunnel Air

The Tunnel Air, or air in tunnels, through which coal-fired locomotives pass, contains many impurities in exceptional quantities, chief amongst which are sulphur dioxide, carbon monoxide and dioxide. In the following table are given the average amounts of sulphur dioxide and carbon monoxide in 10,000 parts of air as found in tunnels in Baltimore, U.S.A., through which steam and electric locomotives, respectively, pass

	Steam Locos.	Electric Locos.
SO2	0.51	0.029
CO	2.67	0.25