NBN EN ISO 1833-4:2010

ISO 1833-4:2006 specifies a method, using hypochlorite, to determine the percentage of protein fibre, after removal of non-fibrous matter, in textiles made of binary mixtures of certain non-protein fibres and one protein fibre, as follows: wool, chemically-treated wool, other animal-hair fibres, silk, regenerated protein fibres based on casein, and cotton, cupro, viscose, modal, acrylic, chlorofibres, polyamide, polyester, polypropylene, glass and elastane.
If several protein fibres are present, the method gives the total of their amounts but not their individual quantities.