Ben Hirst Hazardous Materials Awareness and Operations Practice Exam

Hazard Class 4 covers flammable solids—materials that are solid at room temperature and can ignite readily under certain conditions, such as friction, heat, or moisture, and may also produce flammable vapors when dispersed as dust. The item described as a flammable solid fits this class because it is a solid that can ignite, meeting the criteria for Class 4. The other options describe different DOT hazard classes: a flammable liquid is Class 3, a flammable gas is Class 2, and oxidizing substances are Class 5.1 (they promote combustion but are not themselves flammable solids).