Question 1

A space has been tested and found safe, but the only access is via a long horizontal duct with a single small hatch. What additional planning consideration applies before issuing the permit, beyond a vertical-entry tank?

Accepted Answer

Egress/rescue route and time must specifically account for the restricted, non-vertical access — a stretcher rescue through a small horizontal hatch and long duct takes much longer and needs a tailored plan, not the standard vertical-tank rescue assumption Rescue planning must be specific to the actual geometry of the space — a long duct with a small hatch can make a stretcher extraction extremely slow or require partial disassembly of structure, which must be identified and planned for in advance, not discovered during a real emergency.

Question 2

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

Accepted Answer

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.

Question 3

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

Accepted Answer

No — the company must ensure single-person entry into an enclosed space is not permitted Para. 3.11 explicitly prohibits single-person entry into an enclosed space under any circumstances covered by the recommendation.