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

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

• A. 3
• B. 5
• C. 7
• D. 9

Answer: (B)

The key idea is that oxidizers are a distinct hazard class in the UN labeling system. Substances that readily yield oxygen to support combustion are classified as oxidizers, which is hazard class 5. The number 5 on a label identifies that risk, signaling that the material can intensify fires by supplying oxygen to other fuels. This is different from other hazard classes: for example, 3 marks flammable liquids, 7 marks radioactive materials, and 9 marks miscellaneous dangerous goods. So, labeling an oxidizer with the number five accurately communicates the fire-promoting risk and helps responders take appropriate precautions.

The key idea is that oxidizers are a distinct hazard class in the UN labeling system. Substances that readily yield oxygen to support combustion are classified as oxidizers, which is hazard class 5. The number 5 on a label identifies that risk, signaling that the material can intensify fires by supplying oxygen to other fuels. This is different from other hazard classes: for example, 3 marks flammable liquids, 7 marks radioactive materials, and 9 marks miscellaneous dangerous goods. So, labeling an oxidizer with the number five accurately communicates the fire-promoting risk and helps responders take appropriate precautions.