Tankerman · Safety — Multi-Gas Detector
When testing a cargo tank atmosphere before entry, the correct order of measurement is:
- AAny order — sequence does not matter
- BToxic gases first, then oxygen last
- CFlammable gas only
- DOxygen first, then flammable gas (LEL), then toxic gases (e.g., H2S, benzene)✓ Correct
Explanation
Test oxygen first (combustible-gas meters and toxic sensors depend on adequate O2 to read correctly), then flammability (LEL), then specific toxics such as H2S and benzene. Safe entry generally requires about 20.9% O2, LEL at or below 1%, and toxics below their occupational limits.
Authority: ISGOTT; enclosed-space entry standards
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