DNV

DNV has identified two primary contributors to this issue:

1. Incorrect use of ultrasonic liquid level gauges

Level gauging at temperatures exceeding the manufacturer’s instructions on maximum temperature (CO₂ cylinder temperature) gives unreliable readings. At elevated temperatures, CO₂ converts into a supercritical fluid state, and the cylinder no longer has a liquid level to measure.

2. Bursting disc material

The second issue relates to the material used in the CO₂ cylinder valve bursting disc, to date an issue only observed in systems supplied by NK Co., Ltd. from South Korea up to 2016.

As highlighted in the corresponding Marshall Island Maritime Safety Advisory No. 14-23, service experience has shown that bursting discs made of copper are prone to fatigue failure.

https://www.dnv.com/news/2025/deficiencies-in-co2-fire-extinguishing-systems/