Question 1

Atmosphere test before entry into a cargo hold that previously carried fishmeal: O₂ 20.6%, H₂S 0 ppm, LEL 0%, CO 8 ppm. The STEL for CO is 100 ppm over 15 minutes. The bosun says "CO is well below the STEL — we can go in."

What is the minimum additional requirement before entry proceeds?

Accepted Answer

A CO reading of 8 ppm in a space that has been closed indicates an active CO source — likely biological decay in cargo residues. Entry should not proceed until the source of CO is identified, the space has been ventilated to 0 ppm, and the atmosphere is confirmed stable over two consecutive tests 30 minutes apart A non-zero CO reading is a red flag, not a green light. Any CO in a closed space means an active source exists — incomplete combustion, biological decomposition (fishmeal and grain are common), or chemical reaction with the steel. That source will continue producing CO, and a reading that is 8 ppm at the hatch may be much higher at depth. The STEL is an occupational exposure standard for workplaces, not a "safe to enter" threshold for enclosed spaces with live sources. Confirm stability across two tests, not just one reading.

Question 2

The bosun approaches you — the duty officer — and says he needs to "pop into the pump room for two minutes" to check the bilge level. The gas meter is on charge. No permit has been raised. He says he knows the space well and has done this dozens of times.

What is your response?

Accepted Answer

Stop him. No entry is permitted without a valid atmosphere test and an authorised Enclosed Space Entry permit, regardless of familiarity with the space or duration of entry Familiarity and brevity are the two most lethal attitudes in enclosed space entry. The pump room atmosphere can change in seconds from an undetected gas source. A permit and atmosphere test are mandatory before any entry — COSWP Ch.17 and SOLAS XI-1/7 make no exception for "quick checks". The majority of ESE fatalities involve spaces the victim entered regularly without incident.

Question 3

Pre-entry atmosphere test at the manhole opening of a cargo hold: O₂ 20.5%, LEL 0%, H₂S 0 ppm, CO 0 ppm. The bosun says "It's fine — readings are all in range, let's go in." The hold contained a grain cargo and has been empty for 18 days.

What additional step is essential before entry proceeds?

Accepted Answer

The atmosphere must also be tested at lower levels within the space — at working depth and at the bottom. A safe reading at the entry point does not guarantee safe conditions deeper in the hold Gases heavier than air (CO₂, H₂S) pool at the bottom of cargo holds. Grain cargo self-heats and consumes O₂ through biological activity — the dangerous zone may be the bottom metre of an apparently safe space. COSWP requires testing at multiple levels, especially in spaces with a known biological or chemical cargo history. Testing only at the hatch is a common precursor to fatalities.