(Class 2 Dangerous Goods) A gas is a substance that: (a) at 50°C has a vapour pressure greater than 300 kilopascals (absolute); or (b) is completely gaseous at 20°C at a pressure of 101.3 kilopascals (absolute). Class 2.1: Flammable gases. Class 2.2: Non-flammable, non-toxic gases. Class 2.3: Toxic gases