Maritime Questions › Enclosed Space Entry

What is the normal atmospheric oxygen percentage by volume, and at what reading is an atmosphere generally classed as oxygen-deficient and unsafe to enter?

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. Oxygen percentage is irrelevant if no toxic gas is detected

B. Normal is approximately 18%; readings below 15% indicate deficiency

C. Normal is approximately 20.9%; readings below approximately 19.5–20.0% indicate oxygen deficiency

D. Normal is approximately 25%; readings below 23% indicate deficiency

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

+45 more Enclosed Space Entry questions available

Create a free account to practise all 48 questions, track your accuracy, and build your Reputation Score.

Create Free Account