According to the ERG, there are nine classes of hazardous materials.

According to the ERG, there are nine classes of hazardous materials.

• A. Seven
• B. Eleven
• C. Nine
• D. Five

Answer: (C)

Understanding how the ERG classifies hazardous materials explains why the number is nine. The Emergency Response Guidebook groups hazmat into nine classes to standardize initial response actions at incidents. Those classes are explosives; gases; flammable liquids; flammable solids; oxidizers and organic peroxides; toxic and infectious substances; radioactive materials; corrosives; and miscellaneous hazardous materials. Since there are exactly nine categories, the answer that states nine is the correct one. Choices claiming seven, eleven, or five would either miss two classes, add classes that aren’t part of the ERG scheme, or omit several categories, which is not how the ERG organizes hazmat.

Understanding how the ERG classifies hazardous materials explains why the number is nine. The Emergency Response Guidebook groups hazmat into nine classes to standardize initial response actions at incidents. Those classes are explosives; gases; flammable liquids; flammable solids; oxidizers and organic peroxides; toxic and infectious substances; radioactive materials; corrosives; and miscellaneous hazardous materials. Since there are exactly nine categories, the answer that states nine is the correct one. Choices claiming seven, eleven, or five would either miss two classes, add classes that aren’t part of the ERG scheme, or omit several categories, which is not how the ERG organizes hazmat.