When pumping sour crude, which gas should be tested for prior to entering the cargo pump room to repair a leaking pump?

Correct Answer: Option C — Hydrogen sulfide

Sour crude contains significant concentrations of dissolved hydrogen sulfide, a highly toxic and lethal gas. Before entering a pump room, testing for H2S is a critical safety requirement to prevent accidental exposure, as the gas can accumulate in low-lying areas or be released during maintenance of leaking equipment.