ISO 21870:2005 describes a method for quantitative determination of the loss on heating (pyrolysis) of carbon black due to the elimination of volatile materials other than those liberated when heating to 125 °C (ISO 1126). The method is applicable to carbon black for the rubber industry.

It serves to assess the decomposition of functional groups and adsorbed substances (e.g. hydrocarbons) present on the surface of the carbon black.