This European Standard describes a procedure to detect the use of certain azo colorants that may not be used in the manufacture or treatment of certain commodities made of textile fibres and that are accessible to reducing agent with and without extraction. Azo colorants accessible to reducing agent without extraction are those used to dye: cellulosic fibres (e. g. cotton, viscose); protein fibres (e. g. wool, silk); synthetic fibres (e. g. polyamide, acrylic). Azo colorants accessible with extraction are those used to dye man-made fibres with disperse dyes. The following man-made fibres can be dyed with disperse dyes: polyester, polyamide, acetate, triacetate, acrylic and chlorofibre. For certain commodities made of cellulose and/or protein fibres blended with man-made fibres it is necessary to extract the dye first. The method is relevant for all coloured textiles, e. g. dyed, printed and coated textiles.