Certified Hazardous Materials Manager (CHMM) Practice Exam 2026 - Free CHMM Practice Questions and Study Guide

The designation of hazard classes by the Department of Transportation (DOT) is essential for the safe transport of hazardous materials. Each class is defined by specific criteria related to the nature of the hazards materials present.

Flammable solids, infectious substances, and radioactive materials are all explicitly recognized and classified under the DOT’s hazardous materials regulations. Flammable solids (such as certain types of metals or plastics) are materials that can ignite through friction, heat, or contact with moisture. Infectious substances include materials that may cause disease in humans or animals, and the classification covers a wide range of pathogens. Radioactive materials are substances that emit radiation and pose risks related to exposure.

On the other hand, "friable solid" is not a DOT Hazard Class. While friable materials, such as certain types of asbestos, can pose significant health risks, especially when airborne, they do not fit neatly into the established DOT classes. Instead, the term "friable" describes a property of the material rather than a specific hazard classification under DOT regulations.

Understanding the distinct nature of these classifications is critical for professionals working with hazardous materials to ensure compliance and safety during transport and handling.