What must be checked before enclosed space entry?

Enclosed space entry remains one of the most lethal routine jobs at sea, and the deaths follow a depressingly constant pattern: an unventilated or untested space, and then a would-be rescuer who follows the first casualty in. Treat every cargo hold, tank, cofferdam, void, chain locker, duct keel and any poorly ventilated compartment as an enclosed space until proven otherwise, including spaces that were safe last week.

Before anyone enters, the formal chain must be complete: a risk assessment, an enclosed space entry permit issued by the responsible officer, and a toolbox talk with everyone involved. Isolate anything that could change the atmosphere or endanger the entrants: blank or positively isolate connected lines, lock off pumps and valves, and secure machinery that could start.

Ventilate the space thoroughly, then test the atmosphere from outside using a calibrated and bump-tested meter with a remote sampling line, taking readings at several levels because gases stratify. The acceptance criteria are strict:

• Oxygen at 20.9 to 21 percent by volume, neither depleted nor enriched.
• Flammable gas below 1 percent of the lower explosive limit.
• Toxic gases relevant to the space and its previous contents, such as hydrogen sulphide and carbon monoxide, below their occupational exposure limits.

Continue ventilation during the work, re-test at intervals, and give each entrant a personal gas monitor where required.

The entry arrangements matter as much as the testing. A trained standby person remains at the entrance for the whole job, in continuous communication with the entrants and with the bridge or engine control room, and logs people in and out. Rescue and resuscitation equipment, including breathing apparatus, must be staged at the entrance before entry, and where practicable entrants wear a harness with a retrieval line. The absolute rule, drilled until it is reflex: the standby person never enters to attempt a rescue without breathing apparatus and backup, because that is exactly how a one-casualty accident becomes a multiple fatality. SOLAS requires enclosed space entry and rescue drills at regular intervals precisely so the response is practised, not improvised.

If any reading is doubtful, the meter misbehaves, or conditions change, everyone comes out and the permit is suspended. No sounding, no quick look, no thirty-second job justifies entering an unproven atmosphere; these spaces do not give second chances, and the crews that stay alive are the ones that treat the procedure as absolute.