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The Battery on the Pellets: A Chief Officer, a Gas Detector and a Hold at 3.45% Oxygen

🕑 5 min read words Safety • Incident • Cargo • Enclosed-space

Vessel: SELO — Hong Kong-registered bulk carrier, 20,924 GT, built 2011
Date / Location: 24 July 2025, at sea in the Atlantic, three days out of Savannah, USA, bound for the River Tyne
Cargo: 28,488 tonnes of wood pellets in bulk, in all five holds
Outcome: The Chief Officer was found unconscious on top of the cargo in No. 1 hold and could not be resuscitated
Human Factors: Stale Data Treated as Current · Hasty Entry · Missing Barriers
Source: Hong Kong Marine Department, Marine Accident Investigation Section, report of 30 June 2026

5 decision points · 7 outcome paths · 8 min read

What Happened

SELO left Savannah at 0200 on 21 July 2025 with 28,488 tonnes of wood pellets spread across five holds. The Shipper’s Cargo Declaration said what the cargo does: it depletes oxygen. It also said what to do about it: monitor and record oxygen and carbon monoxide in the holds continuously during the passage, and label every access to the holds as a low-oxygen risk area.

The Chief Officer tested all five holds every day. For three days the log said the same thing: oxygen 20.9%, carbon monoxide 0 ppm, hydrogen sulphide 0 ppm. On the first day the bosun went with him and saw that the gas sampling points on the hatch coamings were blocked by cargo. After that, the Chief Officer tested alone.

On the morning of 24 July he gave the deck crew their jobs: open the ballast tank manholes, and carry out maintenance on the No. 5 hatch covers. At about 0900 he handed the deck cadet a walkie-talkie so he could be reached. At lunch the cadet tried to give it back and could not find him. At 1145 the third officer called for him over the PA. At 1155 the bosun found the hatch entrance to No. 1 hold open and the Chief Officer lying unconscious on top of the pellets.

The master directed a rescue with breathing apparatus, ropes and a stretcher. The third officer entered first, followed by the fitter, and about ten minutes after he was found the Chief Officer was hoisted onto the deck. He had no breathing and no pulse. CPR started at once and continued while the ship diverted to Boston. Resuscitation was stopped at 2216. The medical examiner gave the cause of death as asphyxia due to oxygen deprivation.

At about 1600 that afternoon the crew tested No. 1 hold again. Oxygen: 3.45%. Carbon monoxide: 1,000 ppm. The report cites the IMO recommendation that a safe oxygen level for entering an enclosed space is generally 21% by volume.

What The Investigation Found

No one saw the Chief Officer go into the hold, so the report is careful. It says what it can infer, not what it can prove. Its main findings were:

The earlier readings gave a false picture. Three days of normal results were read as meaning the hold was safe. The report says they did not reflect the known hazard of wood pellets, which steadily deplete oxygen.
The gas test may have been done improperly. The sampling points were blocked by cargo, and no sampling hose was found at the scene. The walkie-talkie was hanging on a door handle near the hatch entrance. The gas detector was lying on deck without its battery. The battery was on the cargo surface close to the Chief Officer.
A likely sequence. The report infers that the battery came off the detector while he was using it, and that he may have gone in hastily to retrieve it and collapsed almost immediately.
The entry procedure was not followed. No risk assessment, no entry permit signed by the master, no one on standby, and no emergency to justify going in. The company was not told.
The barriers were missing. The hatch entrance was neither locked nor marked as a dangerous space, as the Code of Safe Working Practices requires, and the Shipper’s Declaration asked for.
The SMS had a gap. It had no specific procedure for gas testing cargo holds, whether through the sampling points or by an alternative safe method.

The report found no evidence of fatigue, alcohol or drugs. The rest records showed the Chief Officer missed his rest period between 0800 and 0900 on two days, but the investigators did not link that to the accident.

Recommendations (from the report)

The company should circulate the findings to every ship: gas detection must be done correctly, and entry into any space prone to oxygen depletion is forbidden unless it is confirmed safe.
Follow the enclosed space entry procedure in full: risk assessment, entry permit, standby personnel and notification to the company.
Lock or secure the entrances to enclosed spaces and post warning marks, as the Code requires.
Build crew awareness of the fatal risk of enclosed spaces, especially those holding IMSBC Code Group B cargoes.
Write a proper gas sampling procedure into the SMS, covering the case where the sampling points are blocked by cargo.
Audit the ship to confirm the crew follow the enclosed space entry requirements.

Where The Routine Job Broke — Stage By Stage

The daily hold gas test was a routine job, and each stage had a checkpoint that could have caught it. Here is where each stage failed in this case, and what a preventive action looks like.

Stage	How it went wrong here	Preventive action
1. Plan the test	The SMS had no procedure for testing cargo holds. The sampling points were blocked, and no method was written down for that case.	Write the method before the cargo is loaded, including what to do when the sampling points are blocked. Record readings as a trend.
2. Test the risk assessment	Three days of normal readings were taken as proof of safety, although the cargo is known to deplete oxygen progressively.	Treat every hold as an enclosed space from loading. A normal reading is a snapshot, not a clearance.
3. Authorise entry	No permit, no master’s signature. The hatch entrance was unlocked and unmarked.	Lock and mark every entrance. No entry without a signed permit and breathing apparatus.
4. Brief and watch the site	He tested alone, with no one on standby. Nobody knew when or why he went to the hold.	Radio the bridge before and after every test. Have a second person at the hatch. Check the detector and its battery before use.
5. Decide and escalate	A detector failure at the hatch appears to have led to a hasty entry.	A failed instrument is a reason to stop. Step back, get a spare, test from outside.

Human Element Analysis

Stale Data Treated as Current

Three days of normal readings felt like evidence, and the habit of trusting them was strong. Wood pellets are a cargo whose whole hazard is that conditions change over time. A reading is only true at the moment it is taken, and a reading taken from a blocked sampling point may not describe the hold at all.

Hasty Entry

The report infers that a small failure, a battery that came off, led to a fast decision. When a piece of equipment falls into a hazardous space it looks like a ten-second job. That is exactly how a rescuer or a retriever ends up inside. The hazard did not change; the perceived cost of stopping did.

Missing Barriers

The control that would have worked on a rushed day was a locked and marked door. A person who has been working alone for three days relies on habit, and the ship had no physical or procedural barrier to interrupt the habit at the moment it mattered.

Industry	Incident	The Parallel
Aviation	Helios Airways Flight 522, 2005	Crew and passengers lost consciousness from loss of cabin pressure. Hypoxia gives no reliable warning to the person affected, which is why oxygen deficiency is treated the same way in a cargo hold.
Nuclear	Three Mile Island, USA, 1979	An indicator was read as confirming a safe state when it showed only that a command had been given. A reading was trusted over the physical reality it was meant to represent.
Oil & Gas	Deepwater Horizon, 2010	An anomalous test result was explained away until it fitted the expected, safe answer. The test existed to catch exactly that.

Try the Decision Simulator

Take the job from start to finish as the master: the monitoring plan, the risk assessment review, the authorisation and the locked hatches, the equipment and the briefing, and the call when the Chief Officer radios that his detector battery has come off. Work through it in the free Decision Simulator — no login needed to preview. It is a training reconstruction: the investigation never established why he entered the hold, and the scenario says so.

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