Maritime Questions › Enclosed Space Entry

For a space to be entered without breathing apparatus, what minimum standard must the test results show?

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. A "mostly safe" reading is acceptable if the job is urgent

B. Any reading is acceptable provided the entrant wears a basic dust mask

C. Oxygen content alone, regardless of flammable or toxic gas readings

D. Oxygen content normal (approx. 20.9%, generally accepted threshold ~19.5-20% minimum) AND flammable gas reading zero (or below the defined safe threshold) AND any relevant toxic gas below its occupational exposure limit, confirmed by a competent person and recorded on the permit

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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