Full Breakdown
Toxic-Gas Incidents on Frigate HMNZS Te Mana: Inquiry Findings and Navy Response
8/1/2026, 1:03:33 AM
Core Event – Carbon-Monoxide Detections in Wellington Harbour
In late November 2022, the Royal New Zealand Navy frigate HMNZS Te Mana experienced three separate detections of carbon monoxide in a machinery compartment (designated 3M) while berthed in Wellington. On 23 November, two sailors reported a “rotten-egg” smell, left the area, and later recorded 14 ppm of carbon monoxide with a portable detector. The following day, while the ship was maneuvering to Queen’s Wharf in 40-knot gusts, the same sailors re-entered the compartment; their detector alarmed at 48 ppm and a subsequent reading by personnel wearing breathing apparatus peaked at 68 ppm. A third detection occurred later in November under similar conditions.
Investigation Findings – Causes, Health Impact, and Procedural Gaps
A Court of Inquiry, convened after a delay of almost two years, concluded that the most likely source of the gas was the aft sewage-treatment plant, which allowed carbon monoxide to travel 3 m through deck drains into compartment 3M. Expert analysis indicated that the recorded concentrations and exposure durations were unlikely to cause physiological harm, yet the two sailors reported immediate symptoms (headaches, dizziness) and longer-term effects such as disrupted sleep and anxiety. The inquiry attributed these outcomes to a neurofunctional or post-traumatic stress response linked to the sailors’ belief they had been exposed to dangerous levels.
Procedurally, the inquiry identified several failures: a watchkeeper chose not to broadcast a toxic-gas warning despite standard procedure, citing concerns about panic among roughly 30 civilian and military guests aboard for a “shop-window” demonstration. The commanding officer was not informed until after the ship had berthed, preventing him from directing the response. Medical protocols were also breached; after the initial assessment showed normal blood-oxygen levels, the sailors received only paracetamol and no further examination, with higher-level medical care delayed more than 24 hours.
Official Responses and Corrective Actions
A New Zealand Defence Force (NZDF) spokesperson confirmed that all recommendations from the inquiry have been implemented. Modifications include installing a large U-bend in the main gravity line to the sewage-treatment plant during the 2023/24 financial year, expanding toxic-gas training to cover all ship compartments (completed across the fleet between September 2025 and June 2026), and revising standard operating procedures for medical assessment and external treatment. The NZDF also reported no unexplained toxic-gas detections on Navy vessels since the 2022 incidents.
Impact on Sailors and Ongoing Support
Both sailors have undergone neuropsychological assessments as advised by the inquiry and continue to receive rehabilitation support. One sailor missed correspondence while on parental leave and had to arrange his own logistics for recovery. The inquiry emphasized that, while no malingering was evident, the Navy must ensure timely medical evaluation and clear communication during hazardous-gas events to mitigate both physical and psychological harm.
