How Many Hazard Classes Are There - faq-course.com How many classes of hazardous materials are there? Posted: (5 days ago) How many hazard classes does the Department of Transportation have? A visor map guide for state and local law enforcement officials illustrating placards and vehicle markings for the following nine classes of hazardous materials: 1) Explosives, 2) Gases, 3) Flammable liquids and combustible liquids, 4) Flammable ...