The ring-shaped compound benzene (C6H6) belongs to the group of BTEX aromatics. It is liquid, colourless, highly flammable and has a characteristic aromatic odour. Benzene is an important starting product in the petrochemical industry. Its derivatives and secondary products are further processed in paints, pharmaceuticals, insecticides and plastics, among other things. It is also used in fuels (to increase the octane rating). Like all BTEX aromatics, benzene is highly volatile and very mobile. Benzene is classified as carcinogenic and toxic.