Toxic gas from rotting fish waste nearly killed two workers aboard fishing boat

Toxic gas from decomposed fish waste nearly caused the deaths of two workers aboard the fishing vessel Antarctic Discovery while it was undergoing repairs at Lyttelton Port in February of last year. The incident resulted in four individuals requiring hospital treatment, with two workers collapsing due to exposure to hydrogen sulphide, a highly toxic gas produced by decaying organic material. The Transport Accident Investigation Commission (TAIC) has since published its findings, identifying several systemic safety failures that contributed to the near-fatal event. The accident occurred inside the bow thruster machinery space of the Antarctic Discovery, which was docked at Lyttelton Port. Two apprentice fitters were working on a pipe located behind a tank containing a mix of seawater and decomposed fish waste. The offal pump control panel had been repainted, obscuring the labels and indicator lights that would normally show whether the pump was operational. Investigators determined it was “as likely as not” that one of the apprentices inadvertently activated the offal pump, leading to a sudden release of contaminated water onto the workers. The two fitters had no choice but to climb up a ladder through the falling waste to reach open air. They managed to alert others, prompting the vessel’s superintendent to enter the bow thruster room to investigate. He was briefly overcome by the hydrogen sulphide gas. Soon after, the chief engineer and second engineer arrived from another location and both collapsed. Rescue efforts ensued, with the chief engineer requiring assistance via breathing apparatus, while the second engineer regained enough awareness to crawl to safety. Hydrogen sulphide is a colorless, flammable, and extremely toxic gas with a distinct odor resembling that of rotten eggs at low concentrations. However, at higher levels, it can cause a person to lose their sense of smell, making it difficult to detect the presence of the gas. Exposure at these levels can lead to respiratory failure and death within minutes. TAIC noted that maritime safety authorities had previously warned about the dangers of hydrogen sulphide generated from decaying fish and seawater in refrigerated tanks or fish holds, particularly under warmer conditions. Fatalities have frequently occurred during rescue operations due to the gas’s rapid effects. The TAIC investigation traced the root causes back to a series of lapses in safety procedures. A month prior to the incident, the Antarctic Discovery had encountered a blockage in a valve designed to discharge fish waste from the forward tank. To resolve this, a temporary hose was used to transfer the waste to another tank. However, the hose was incorrectly left connected to the offal pump, with its open end tied to a ladder leading into the bow thruster room. Additionally, the tank’s outlet remained open, and the offal pump was not properly isolated. Acting Chief Investigator Tahlia Fisher emphasized that the primary issue was not merely the accidental activation of the pump, but rather the failure to deactivate the offal pumping system when it should have been. She pointed out that the bow thruster machinery space posed the same hazards as an enclosed or confined space, yet it had not been recognized or managed accordingly. Fisher added that when multiple organizations operate in the same workspace, safety relies heavily on active coordination among all parties involved. The TAIC identified four key safety concerns arising from the incident: the proper identification of hazards in confined spaces, ensuring machinery is safe before commencing work, adhering to correct procedures when modifying critical safety systems, and maintaining clear risk management practices when multiple entities share a worksite. These recommendations extend beyond the fishing industry, highlighting potential vulnerabilities in other sectors as well. The investigation also revealed that the Antarctic Discovery had undergone modifications to its offal pumping system shortly before the incident. These changes were not adequately documented or communicated, contributing to confusion among the workers. Maritime New Zealand has separately looked into the incident, though specific findings from their inquiry remain pending. The TAIC’s report underscores the need for stricter adherence to safety protocols, particularly in environments involving hazardous materials and confined spaces.