Azo colorants that are able to form 4-aminoazobenzene, generate under the conditions of ISO 24362-1:2014 the amines aniline and 1,4-phenylenediamine. The presence of these 4-aminoazobenzene colorants cannot be reliably ascertained without additional information (e.g. the chemical structure of the colorant used) or without a special procedure.

ISO 24362-3:2014 is supplementary to ISO 24362-1:2014 and describes a special procedure to detect the use of certain azo colorants in commodities, which may release 4-aminoazobenzene, accessible to reducing agent without extraction, particularly concerning textiles made of cellulose and protein fibres (e.g. cotton, viscose, wool, silk); accessible by extracting the fibres (e.g. polyester or imitation leather).

For certain fibre blends both parts of ISO 24362 (without or with extraction) may need to be applied.

The procedure detects as well 4-aminoazobenzene (Solvent Yellow 1) which is already available as free amine in commodities without reducing pre-treatment.