When H2S has been encountered on a MODU, or is anticipated, monitoring devices must sound an alarm (which differs from the lower concentration alarm) or otherwise warn employees when concentration of H2S reaches or exceeds how many parts per million?

Correct Answer: Option B — 50

Under BSEE/MMS regulations, H2S monitoring systems must provide a distinct, high-level alarm at 50 ppm. This threshold is set to warn personnel of immediate danger, requiring the immediate use of self-contained breathing apparatus (SCBA) and the initiation of emergency response procedures to protect the crew from toxic exposure.