BSafe Case Study 15 — The CO2 Seemed to Work. The Fertiliser Kept Reacting Anyway.

Smoke With a Chemical Smell, Not Heat

Loaded with various fertilisers in the lower holds and general cargo in the tween decks, the ship was anchoring after departure when the master spotted white smoke from cargo hold No. 3. The chief officer's team found it emerging from the hold's fan cowls, with a chemical odour and no apparent heat. An AB in full fire protection gear tried to enter but aborted when he sensed smoke inside his own mask.

A Fix That Looked Like It Worked

The crew identified the cargo as ammonium nitrate-based fertiliser in the lower hold, alongside machinery parts in wooden crates on the tween deck. After consulting the company's designated person, they released the hold's fixed CO2 system. The smoke visibly reduced — and the crew believed the situation was now stable. It wasn't. Ammonium nitrate decomposition is a self-sustaining exothermic chemical reaction; smothering the visible smoke with CO2 doesn't stop the underlying reaction generating it.

A shoreside firefighting team, dispatched by helicopter, recognised the decomposition risk and decided the only real fix was to flood the hold — opening the hatch cover and pumping water in from a firefighting vessel. As they began, a massive burst of yellow smoke emerged, raising real concern about an imminent explosion. The ship was fully evacuated. Over the following days, with three firefighting vessels assisting, hold No. 3 was successfully flooded, finally halting the decomposition. The ship, badly damaged, was towed for unloading and declared a total constructive loss. No fatalities or serious injuries occurred, though crew and firefighters were taken to hospital for observation after smoke exposure.

What This Illustrates

• A fixed CO2 system reducing visible smoke was read by the crew as evidence the problem was resolved — when the underlying hazard, a self-sustaining chemical decomposition, doesn't respond to a suppression method built for a normal combustion fire.
• Ammonium nitrate-based fertiliser carries a real, well-documented decomposition risk independent of any external ignition source — the hazard originates in the cargo itself, not from something that can simply be extinguished.
• Recognising this required specialist shoreside expertise — the crew's own read of the situation, reasonable given the tools available to them, wasn't sufficient to correctly diagnose what was actually happening.
• The eventual solution — deliberately flooding a cargo hold — is itself an unusual, high-consequence decision, underlining how different this hazard was from a standard fire response.

Recommended Actions

Grounded in what this incident actually shows:

1. Any cargo capable of self-sustaining decomposition (ammonium nitrate-based fertilisers among them) needs its specific hazard profile understood before loading — a visible-smoke response plan built for ordinary fire doesn't match this cargo's actual behaviour.
2. A fixed gas suppression system reducing visible symptoms should be treated as inconclusive for a decomposing-cargo scenario, not as confirmation the hazard is controlled — specialist advice should be sought early, not after the situation visibly worsens again.
3. Crews carrying cargoes with known self-reactive properties benefit from pre-briefed awareness of what shoreside/specialist responses (like deliberate flooding) might actually be required, so an escalating decision doesn't come as a surprise mid-emergency.

Human Element Analysis

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Related Reading

• BSafe Case Study 10 – another real total-loss fire, a different cause, the same lesson about closing the loop under pressure