Aryl azo connected at both ends of a class of organic compounds. Azo dyes in the synthesis of a class of most varieties are widely used in a variety of natural and synthetic fibers, dyeing and printing, also used in paints, plastics, rubber, coloring. Azo dyes may release aromatic amines, aromatic amines are some harmful substances. Azo electronic products related to the product or packaging is mainly used in fabric, leather, other, paint, plastic, rubber, coloring is also useful to.
 
REACH Annex 17 Chapter 43 and 22 species listed in Appendix Ⅷ aromatic amine dyes, limiting its use. Limit is 0.003% (each an aromatic amine in the final product or part of the mass ratio of dye). Consistent with the REACH Directive 2002/61/EC.

In addition, some standard limit of 24 aromatic amines.
Please note that not all of the azo fuels are harmful to the current limit of only 22 kinds (or 24 kinds), limited concentration of each substance is not more than 0.003%, and not all substances.