Which type of material might explosively decompose if concentrated?

• A. Flammable
• B. Pyrophoric
• C. Peroxide forming
• D. Combustible

Answer: (C)

Concentration-related explosive hazard arises most with peroxide-forming materials. When some organic compounds are exposed to air or over time, they can form organic peroxides. These peroxides are unstable and can decompose violently, especially if the material is concentrated, heated, or subjected to shock or friction. The energy stored in the peroxide bond can be released rapidly, producing an explosion as gases rapidly form and build pressure.

Flammable substances can ignite and burn, but that’s a flame hazard rather than an explosive decomposition upon concentration. Pyrophoric substances ignite spontaneously in air, not typically due to concentrating a material to form peroxides. Combustible simply means capable of burning under the right conditions, not necessarily explosive on concentration. Peroxide-forming materials uniquely carry the risk of explosive decomposition when their peroxide content becomes concentrated.