The Transport Accident Investigation Commission of New Zealand (TAIC) has published its report on its investigation into the gas poisoning that had occurred on the Australian-flagged longline fishing vessel Antarctic Discovery on February 21, 2025.
In January 2025, Antarctic Discovery was at sea when a valve for discharging fish waste from the forepeak tank into the sea became blocked. Its chief engineer installed a temporary hose to pump to another tank.
The crew finished that pumping work but left the first section of hose connected to the offal pump with its open end tied near the top of a ladder that gave access down to the vessel’s bow thruster machinery space, just aft of the forepeak tank.
On February 21, the vessel was in dry dock in Lyttelton for maintenance. Two apprentice fitters descended the ladder to the bow thruster machinery space to work on pipe components.
The switch panel for the offal pump was immediately adjacent. The TAIC said it is about as likely as not that one of the fitters accidentally pressed the pump’s unlabelled start button.
Water contaminated with rotting fish offal rained down on them from the hose’s open end at the top of the ladder. Foul-smelling toxic hydrogen sulphide gas (a known by-product of decaying fish) began building up.
The fitters climbed the ladder through the falling contaminated water and escaped to the open air.
The fitters raised the alarm. The vessel superintendent investigated the scene and was briefly overcome by gas. The chief engineer and second engineer came from another direction and collapsed. Crew using breathing apparatus rescued the chief engineer.
Four affected workers were taken to hospital and later recovered.
While the cause of the accident was activation of the pump, the TAIC’s report details a combination of four systemic safety issues that made it more likely.
Making machinery safe before work begins (lockout/tagout)
Vessel owner Australian Longline’s safety procedures for lockout/tagout focused on equipment being worked on, but not nearby systems that could create hazards if activated. In this case, the valve for the forepeak tank outlet was left open, not closed; the offal pump was left ready to go with its discharge side open – not isolated and locked and tagged out.
The TAIC said that lockout/tagout procedures need to cover not just the system being worked on, but also any nearby systems that can create a hazard.
Enclosed and confined spaces
The bow thruster machinery space had characteristics of an enclosed and confined space, but it had not been identified as such. People working there were at greater risk of harm from toxic gas or flooding with limited ability to escape.
The TAIC said the hazards determine the controls. If a space has the hazards or characteristics of an enclosed or confined space, it should be managed as such.
Multiple organisations, same workplace
Accidental discharge of hazardous liquids and the resulting gases can create hazards for dry dock workers. Lyttelton Port Company’s safety standards and management of dry dock workers did not provide adequate protection from this hazard.
TAIC said safety responsibilities can overlap if several organisations work at the same site. Also, the work can change from day to day. Safety depends on active coordination for everyone to understand the hazards, who controls them, and management of change.
The commission has recommended that Lyttelton Port Company (operator of the dry dock) ensure that systems on dry-docked vessels that could affect dry dock safety are isolated and kept safe and improve management of overlapping responsibilities of parties working in its dry dock.
Modification of safety-critical systems
This vessel’s forepeak tank had been modified using materials that compromised the vessel’s watertight integrity and the safety of its crew. The modification was not approved by the vessel’s classification society and was missed in multiple class surveys. Australian Longline’s safety management system did not ensure modifications to safety-critical systems were approved by shoreside management and class.
Repairs and modifications to safety-critical systems need the right approval, documentation and oversight. The TAIC said class standards exist because vessel owners and class providers both play a part in ensuring and maintaining approved standards.
The commission has recommended that Australian Longline strengthen approval processes for proposed modifications to all safety-critical systems.
Safety actions by Australian Longline
Australian Longline has already taken extensive safety action, including strengthening isolation procedures, contractor induction, toolbox meetings, enclosed-space registers and the offal pumping system. TAIC said it welcomes these actions as they reduce the likelihood of a similar accident.