Under the UN labeling system, a substance that readily yields oxygen to support combustion of fuels would be labeled with which number?

Under the UN labeling system, a substance that readily yields oxygen to support combustion of fuels would be labeled with which number?

• A. 3
• B. 1
• C. 7
• D. 5

Answer: (D)

Under the UN labeling system, hazard classes are identified by numbers that show the type of danger. Substances that readily yield oxygen to support combustion are oxidizers, which are classified as Class 5. So the label number for such a substance is five. The other options correspond to different classes—three for flammable liquids, one for explosives, seven for radioactive materials—and don’t describe an oxidizer.

Under the UN labeling system, hazard classes are identified by numbers that show the type of danger. Substances that readily yield oxygen to support combustion are oxidizers, which are classified as Class 5. So the label number for such a substance is five. The other options correspond to different classes—three for flammable liquids, one for explosives, seven for radioactive materials—and don’t describe an oxidizer.