EnglishON 20 JANUARY 2024, WHILE A SHIP WAS UNDERWAY AFTER DISCHARGING BENZENE, A CREW MEMBER ENTERED A CARGO TANK BEFORE ENCLOSED-SPACE ENTRY PROCEDURES HAD BEEN AUTHORISED AND BEFORE CONFIRMING THE ATMOSPHERE WAS SAFE. HE WAS LATER FOUND COLLAPSED AT THE BOTTOM OF THE TANK AND, DESPITE RESCUE EFFORTS, DID NOT SURVIVE. THE INVESTIGATION REPORT CONCLUDED WITH THE PRESUMPTION THAT RESIDUAL BENZENE VAPOURS AND OXYGEN-DEFICIENT ATMOSPHERE WITHIN THE TANK WERE THE PRIMARY FACTORS LEADING TO HIS RAPID INCAPACITATION AND SUBSEQUENT FATALITY.
Source KMST MSI REPORT 2024-002
INCIDENT OVERVIEW
BACKGROUND OF SHIP AND VOYAGE DETAILS
An 8,270 gt oil/chemical tanker had discharged benzene on its previous voyage and was proceeding in ballast towards Korea to load its next nominated cargo. The ship had completed discharge at Jiangyin, China and departed for Yeosu, Korea. The planned sequence between voyages included a full cycle of gas freeing and cleaning of cargo tanks in preparation for the next chemical cargo.
The final part of the cleaning process required physical tank entry to conduct manual wiping or “mopping”, of any residual wash water. As is standard, tank entry required an enclosed space entry permit to be issued by the master. This company’s policy was to mark the hatch cover of the space to show that a permit had been issued, and it was now safe for entry.
Some of the cargo tanks had previously carried benzene. Although the tanks had been rinsed and ventilated for gas freeing, residue benzene vapours remained a serious hazard. Benzene is highly volatile and toxic; in a confined or poorly ventilated environment, inhalation can rapidly cause dizziness, incapacitation, collapse, respiratory failure or fatal exposure.
The ship had a multinational crew, with personnel from Korea, Indonesia, and Myanmar.
WHAT HAPPENED
On the morning of the incident, the ship was several hours into the passage. Preparations were underway for the “mopping” stage of tank cleaning. This stage typically occurs only after gas freeing has progressed sufficiently and the tank atmosphere has been gas tested and verified safe.
At around 1010 hrs the chief officer (C/O) instructed four deck ratings (bosun, able seaman, and two ordinary seamen) to bring mops and rags to the main deck in preparation for mopping operations which were planned to take place inside the washed cargo tanks. At this point, the “enclosed space entry permit” process had not yet been initiated, and no confirmation had been made that the tank atmosphere was safe. It is understood that the C/O had noted a strong smell of cargo residue from within the cargo tanks at deck level, and had therefore felt it unnecessary to test the atmosphere as it was clearly still unsafe.
Shortly afterwards, one of the ordinary seamen (OS) appears to have acted ahead of the authorised sequence. They entered the cargo tank through an open hatch, before the atmosphere had been tested and confirmed safe. It was later discovered that they were not carrying a portable multi-gas detector and was instead wearing a filter-type mask, presumably as “protection”. The filter-type mask worn offered no protection in an oxygen-deficient space and could not protect against residual benzene or other toxic vapours that might still linger inside the tank.
Around 1035 hrs, the bosun, who was walking across the deck, looked down into cargo tank 10 Port. Seeing the OS lying collapsed on the tank bottom, the bosun immediately raised the alarm. The bridge informed the master, and shipboard emergency response commenced.
Source KMST MSI REPORT 2024-002
The C/O and second officer donned Self Contained Breathing Apparatus (SCBA) and entered the tank to recover the OS. They fitted the OS with an Emergency Escape Breathing Device (EEBD) but he remained unresponsive. The OS was brought up to deck level on a stretcher and CPR was initiated, with medical support sought from the shore rescue authorities. Despite prolonged resuscitation efforts, the OS did not regain consciousness and was later declared deceased upon hand-over ashore.
The subsequent autopsy identified traumatic injury consistent with a fall onto a hard surface, including cervical spinal fracture – meaning the atmosphere incapacitated the OS before they had reached the bottom. Benzene was detected in the OS’s cardiovascular system. Based on this, and the fact that the tank bottom was only accessible by ladder, it was determined that the OS had entered the tank of their own volition, inhaled residual benzene vapours, collapsed inside the tank and fell, sustaining fatal injury. The tank atmosphere had not been tested and confirmed safe prior to entry, and the filter-type mask worn by the OS was not suitable or approved for protection against benzene vapours or oxygen-deficient atmospheres.
This event developed rapidly and at a point where the tank had not yet been formally cleared for entry. Until an enclosed space permit is issued, a cargo tank must be treated as hazardous, regardless of whether the hatch is open, a fan is running, or the tank has been recently washed.
The purpose of the permit process is to confirm, through measured data and recorded gas testing, that it is safe to proceed. Tanks may look harmless from above yet can still harbour atmospheres that can quickly incapacitate or kill without warning. Therefore, visual appearance from the deck level cannot be relied upon; the atmosphere within a tank can remain dangerous even when it seems inactive or benign.
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