Maritime Questions › Enclosed Space Entry

Once a permit has been issued and entry has begun, how should the atmosphere be monitored for the duration of the work?

Q: Under MSC.581(110), what is the maximum acceptable CO2 reading (by volume) before an enclosed space can be considered safe for entry?

Less than 0.5% by volume (5,000 ppm) Para. 7.4 sets the CO2 exposure limit at below 0.5% by volume (5,000 ppm) before entry; if this is not achieved, the space remains unsafe. CO2 is now explicitly addressed as a major asphyxiation hazard alongside oxygen depletion.

A. Re-test once, at the midpoint of the job, regardless of duration

B. Re-test only if someone reports feeling unwell

C. Continuously, either by a fixed/portable monitor inside the space or by repeated periodic testing at a frequency set by the risk assessment — a single pre-entry test is not sufficient on its own

D. No further testing is needed once the pre-entry test passes

Under MSC.581(110), what is the maximum acceptable CO2 reading (by volume) before an enclosed space can be considered safe for entry?

A. Less than 0.5% by volume (5,000 ppm)

B. Less than 2% by volume

C. Less than 21% by volume

D. There is no specific CO2 limit, only an oxygen limit

Under the revised recommendations, is single-person entry into an enclosed space ever permitted?

A. No — the company must ensure single-person entry into an enclosed space is not permitted

B. Yes, provided the person carries a personal gas detector

C. Yes, for spaces that have previously tested safe within the last 24 hours

D. Yes, but only for spaces below 5 metres in depth

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