A substance that spontaneously releases ionizing radiation would be labeled a hazard class under the UN Labeling System as which class?

• A. Class 5
• B. Class 7
• C. Class 3
• D. Class 1

Answer: (B)

Hazard classes in the UN labeling system are grouped by the primary danger a material poses. A substance that spontaneously releases ionizing radiation is categorized as Class 7 because radioactive materials require special handling, shielding, and monitoring to protect people from radiation exposure. That radiation-specific hazard is distinct from other dangers like explosions, flammable liquids, or oxidizers, which fall into their own classes. Explosives are Class 1, flammable liquids are Class 3, and oxidizers are Class 5, none of which describe radioactive emission. So the appropriate classification for a material that continuously emits ionizing radiation is Class 7.