Hydrogen Sulphide on Board Ships
Sources of H2S aboard, olfactory fatigue, the occupational exposure limits that apply, and the tank and hold cases where it has killed.
Hydrogen sulphide is one of the four gases SOLAS regulation XI-1/7 requires a ship’s portable atmosphere testing instrument to measure. It occurs in crude oil of most grades, in sewage and slop tanks through bacterial sulphate reduction, in some chemical cargoes, and in solid bulk cargoes that decompose in a hold. It is heavier than air and collects at the lowest point of a space.
MSC.581(110) sets no gas-specific figure for it: paragraph 7.4.4 requires any toxic vapour or gas to be below 50 percent of its occupational exposure limit, and the applicable limit depends on the national list the flag state points at. IACS Recommendation No. 72 Rev.4 publishes figures for survey work of 5 ppm over an eight-hour shift and 10 ppm over 15 minutes.
The full article will cover the detection problem created by olfactory fatigue at higher concentrations, the sources aboard by ship type, sensor selection and cross-sensitivity, and the investigation record. The cargo hold access space in which three stevedores died on the Berge Mawson on 27 June 2022 was found to be oxygen deficient and high in hydrogen sulphide, per MAIB report 5/2025.