H_2S - dangerous at almost any concentration

摘要

During a recent Port State Control (PSC) tank vessel examination it was requested that cargo tank oxygen levels be verified using the ship's portable gas meter. The vessel was carrying grade E sour crude. When the deck sounding valve was opened, the pressurised cargo tank atmosphere escaped, releasing inert gas and H_2S (hydrogen sulphide) vapours. During the evolution the personal gas meters of two individuals alarmed for H_2S. One whose alarm sounded was standing 1-2ft (0.3-0.6m) downwind from the sounding valve. Within days, this person developed severe exposure symptoms consistent with H_2S exposure.