HazMat Awareness and Operation Practice Exam

Flammable solids are assigned to hazard class four. UN labels and placards use the class number to identify the type of hazard, so a container of flammable solids will carry the four on its label. This distinguishes it from other common classes: gases are class two, flammable liquids are class three, and toxic substances are class six. Hence the appropriate hazard classification number on the label is four.