Four hospitalised after toxic gas from rotting fish waste knocks engineers unconscious

Thursday, 23 July 2026

The Antarctic Discovery was in Lyttelton dry dock for routine maintenance when four workers were hospitalised after hydrogen sulphide gas was released from decomposing fish waste.

Four workers were hospitalised after hydrogen sulphide gas was released during routine maintenance aboard the Antarctic Discovery.

Investigators found it was “about as likely as not” an apprentice fitter accidentally started the offal pump by pressing an unlabelled button that had been painted over.

The Commission said the quick actions of the vessel’s superintendent and second mate “likely saved the lives” of two engineers who collapsed in the toxic atmosphere.

Four workers were admitted to Christchurch Hospital after “foul liquid started raining down” inside a fishing vessel, releasing toxic hydrogen sulphide gas that caused two engineers to collapse during routine maintenance in Lyttelton.

A Transport Accident Investigation Commission report has found the near-fatal incident aboard the Antarctic Discovery in Lyttelton dry dock on February 21, 2025, most likely began when an apprentice fitter accidentally pressed an unlabelled start button that had been painted over.

Within minutes, contaminated water from a tank that had previously stored decomposing fish offal was pumped through an open-ended hose, releasing hydrogen sulphide into the vessel’s forecastle.

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“The first indication that something was amiss was when a foul liquid started raining down from the top of the access ladder,” the commission found.

Two apprentice fitters climbed out of the space and raised the alarm after the flow intensified and developed a foul odour.

The vessel’s superintendent entered the forecastle to investigate but, after taking only a few steps, suddenly felt dizzy. They retreated to the open deck and collapsed into a semi-conscious state.

A Transport Accident Investigation Commission inquiry found a series of safety failures contributed to the toxic gas incident aboard the Antarctic Discovery.

The chief engineer and second engineer then entered the forecastle through another entrance.

The commission found they “collapsed simultaneously” after being overcome by the toxic atmosphere.

The second engineer later regained enough consciousness to crawl to safety, while the superintendent and second mate donned breathing apparatus and returned to rescue the unconscious chief engineer.

“The quick and decisive action taken by the vessel superintendent and second mate likely saved the lives of the workers who were overcome by the hydrogen sulphide,” the report said.

The two engineers and two apprentice fitters were admitted to Christchurch Hospital with symptoms of hydrogen sulphide exposure. All recovered and were discharged later that day.

Investigators found it was “about as likely as not” that one of the apprentice fitters unintentionally activated the offal pump while working immediately beside its control panel.

The panel had been painted white, obscuring the labels identifying the start and stop buttons and the indicator light showing when the pump was operating.

The apprentices were also listening to a portable stereo while they worked.

“It is about as likely as not that the background noise and the absence of a visible pump-running indicator light limited their ability to detect that the pump was active,” the report said.

Investigators said it was “virtually certain” the offal pump had been started, drawing contaminated water containing fish offal residue and sludge from the tank. Although the tank had been rinsed several times after the fishing trip, residue remained at the bottom. After 11 days in warm summer conditions while the vessel sat in dry dock, those conditions were conducive to the formation of hydrogen sulphide.

Hydrogen sulphide is a colourless, highly toxic gas produced when organic matter decomposes without oxygen. It is known for its rotten egg smell at low concentrations, but at higher levels it can rapidly cause unconsciousness, respiratory failure and death.

The commission found multiple safety failures contributed to the incident.

The offal pump had not been isolated or locked out before maintenance began, allowing it to be accidentally started. The bow thruster room also had many of the characteristics of an enclosed or confined space but “had not been identified as such”, meaning additional safety controls, including atmospheric testing and confined space entry procedures, were not in place.

The report also found the vessel’s offal pumping system had been modified without approval from classification society DNV, despite remaining in use for years.

The incident was not the first involving the vessel’s operator.

In 2012, a crew member aboard Australian Longline’s Antarctic Chieftain was found dead in a forepeak tank that had previously contained fish offal. A coroner found drowning was the cause of death, with inhalation of hydrogen sulphide a contributing factor.

The commission has recommended Australian Longline strengthen its approval process for safety-critical modifications. It has also recommended Lyttelton Port Company take steps to verify hazardous onboard systems are isolated before vessels enter dry dock and improve how multiple organisations coordinate health and safety during maintenance.