Which statement describes Division 5.1?

• A. Organic substances that are thermally unstable and can undergo exothermic, self-accelerating decomposition
• B. Oxidizing Substances that yield oxygen
• C. Gases
• D. Inert materials

Answer: (A)

Division 5.1 is about oxidizing substances—materials that can release oxygen or provide oxygen to participate in a reaction and thus promote or intensify combustion. The statement that best describes Division 5.1 is that these are oxidizing substances that yield oxygen, since that oxygen-supporting property is the defining characteristic of this division.

The other description refers to organic peroxides: organic substances that are thermally unstable and can undergo exothermic, self-accelerating decomposition. That describes Division 5.2, not Division 5.1, which is why it doesn’t fit. The option about gases points to Class 2, and the inert materials option doesn’t define a hazardous-oxidizer class.