All combustible gases and vapours are categorised according to their ignition temperature.
The ignition temperature (also known as ignition point, auto-ignition temperature, flash-point) is the temperature to which a material or a contact surface must be heated so that a combustible substance (solid material, fluid, or their vapours or gases) in the presence of air without sparks, solely as the result of being heated – i.e.: without a source of ignition - ignites itself.
Some examples of ignition temperature:
All electrical and mechanical explosion protected operating facilities must be classified into Temperature Classes in accordance with their maximum surface temperature.
The maximum surface temperature must thus be constantly below the ignition temperature of the surrounding gas or alternatively vapour-air mixture.
For electrical and mechanical operating facilities in a dust atmosphere, classification according to temperature is not compulsory.
The Temperature Classes are laid down in IEC Standard 60079-0.