Which hazard class number corresponds to oxidizers (substances that readily yield oxygen to support combustion)?

• A. 5
• B. 4
• C. 6
• D. 8

Answer: (A)

Oxidizers release oxygen to help other materials burn. Because of this, they’re assigned to hazard class five, signaling that they can cause, accelerate, or sustain fires even without a flame present. This classification helps emphasize safe handling: keep oxidizers away from fuels, organic materials, and reducing agents; store them separately; and control heat and confinement to prevent violent reactions. Organic peroxides are related but sit in a related subcategory under the same general class. Other hazard classes correspond to different dangers (such as corrosives or toxic substances), so they don’t describe oxidizers.