AWO Near Miss 23-16 – High Levels of H2S in Cargo Tanks

During crew change, the off-going crew had mentioned there was H2S in the Coker Heavy Gas Oil (CHGO) cargo tanks, 2P/S and 5P/S. The C/M, suited in proper PPE and full-face respirator, was able to get a reading of ~115PPM H2S in the cargo tanks. At this PPM, it is considered Immediately dangerous to life and health (IDLH) for the crew. This was likely caused by heating the cargo, which increases tank pressure, making the H2S more concentrated.

After being notified, the captain contacted shoreside operations to inform them about the high H2S. The crew conducted a safety meeting to discuss H2S hazards and precautions, as well as safety zones and muster points. The captain notified the chartering group and the port captain to relay the high H2S readings to the dock and gauging company that all connections and gauging should be completed while on SCBA air.