Referring to the United States Military Marking System for Hazardous Materials, an octagon shaped placard with a #1 on it denotes a:

• A. Moderate fire hazard.
• B. Mass explosion/detonation.
• C. Chemical fire hazard.
• D. Mass escape.

Answer: (B)

In the United States Military Marking System for Hazardous Materials, shapes and numbers convey the specific type of hazard. An octagon communicates an explosive hazard, and the numeral on it identifies the category. The numeral 1 on an octagon indicates a mass explosion/detonation risk, meaning the material could detonate and affect a large area. That’s why this placard best matches the option describing mass explosion/detonation.

It doesn’t denote a moderate fire hazard or a chemical fire hazard, which would be indicated by different markings, and “mass escape” isn’t the hazard category represented by this symbol.