Coal Gas is gas manufactured by the destructive distillation of bituminous coal. The chief components are hydrogen (more than 50%), methane (10% to 30%) carbon monoxide and higher hydrocarbons. The water vapour in coal gas kept old pipe joints tight, thus minimising loss of gas. If natural gas is introduced into the same pipes without remedial action substantial losses may occur. The carbon monoxide is of course poisonous. Inhaling coal gas was a favoured way of committing suicide in cities with coal gas distribution.