Gas detection, enclosed spaces and calibration

Ships still lose people in their holds, tanks, chain lockers and store rooms. The air in these spaces looks normal, has no smell and kills in minutes. InterManager’s analysis for the IMO, covering 1996 to May 2026, puts 47% of enclosed space accidents in cargo holds and their access ways, and finds that most happen during work that had been planned. Many victims are the rescuers: in the Sally Ann C casualty in 2015, the chief officer, then the chief engineer, then the second officer went into the same hold access without breathing apparatus. Oxygen there was later measured at 3.5%.

The rules have tightened. Since 1 July 2016, SOLAS regulation XI-1/7 has required every ship to carry a portable instrument that measures oxygen, flammable gas, hydrogen sulphide and carbon monoxide, with a suitable means of calibrating it. Since 1 January 2015, crew with entry or rescue duties have had to take part in an enclosed space drill at least once every two months. In June 2025 the IMO adopted resolution MSC.581(110). It replaces resolution A.1050(27) and adds a ship-specific Enclosed Space Register, a carbon dioxide limit before entry and an eight-hour limit on entry permits.

This course follows the equipment from the shelf to the space: how the portable meter is chosen and used, why a bump test is not a calibration, which fixed systems tankers and gas carriers must have, how a safe entry is run step by step, and how gas-tight chemical suits are checked. At the end you will be able to check a ship’s gas detection arrangements against the rules, as an officer, superintendent, technician or surveyor would.