Detecting cargo self-heating before smoke appears

November 16 ------ Two hopper barge fires involving wood pellet cargoes containing binders highlight the dangers of spontaneous combustion and the importance of detecting cargo deterioration before a fire develops.

In its MARS 202637 report, published on 30 October 2026, The Nautical Institute revisits incidents previously investigated by the US Coast Guard (USCG), in which both barges suffered extensive damage while awaiting transport. The cases demonstrate how moisture exposure, prolonged storage and insufficient early detection can create serious cargo safety risks.

What happened

According to the USCG’s original Safety Alert 10-23, issued in November 2023, two unmanned and uninspected hopper barges carrying wood pellets containing binders caught fire within a two-week period while awaiting transport at a Mississippi River fleeting facility. Both fires resulted from spontaneous combustion, with each incident causing approximately $355,000 in damage, including the complete loss of cargo and substantial damage to the barges.

Following the incidents, assessments of other wood pellet barges at the facility identified several potentially dangerous conditions, including visible moisture, deteriorating and discolored cargo, and elevated temperatures reaching approximately 75°C.

Cargo decomposition was also associated with the generation of carbon monoxide and hydrogen sulphide. The USCG indicated that some of these conditions probably existed before the two fires. However, the first recognized warning sign was smoke emerging from pellets that were already smoldering.

As temperatures increased, heat from the burning cargo melted the hopper covers, allowing additional oxygen to reach the affected material. This accelerated the fire’s development, resulting in rapid and uncontrollable fire growth.

What went wrong

The USCG identified spontaneous combustion as the ignition source in both incidents, but did not establish the precise moisture conditions or individual operational failures that contributed to each fire.

The International Maritime Solid Bulk Cargoes (IMSBC) Code identifies that wood pellets containing additives or binders can undergo fermentation when moisture content exceeds 15%. This process may produce asphyxiating and flammable gases and create conditions conducive to spontaneous combustion. The incidents highlight the importance of monitoring cargo condition before visible signs of fire emerge.

Although elevated temperatures, deterioration and gas generation were identified during subsequent assessments of other barges, the first recognized indication in the affected cargoes was smoke. By that stage, self-heating had already developed into smoldering combustion, significantly reducing the opportunity for early intervention.

The melting of the hopper covers further complicated the situation by allowing additional oxygen into the cargo spaces, intensifying the fires. The case illustrates how a failure to recognize developing cargo hazards early can leave operators responding to an established fire rather than preventing ignition.

The big picture

The implications extend beyond unmanned barges to bulk carriers and other vessels transporting wood pellets or cargoes susceptible to self-heating. Wood pellets may appear relatively stable during loading and storage, but their condition can deteriorate depending on moisture exposure, cargo characteristics and the duration of storage.

A particular concern is that cargo deterioration may progress without obvious external indications, making appropriate monitoring arrangements essential.

Similar hazards were highlighted in a previous SAFETY4SEA Lessons Learned report concerning damp animal feed pellets. In that case, water ingress and condensation were associated with cargo heating and smoldering, eventually resulting in a significant cargo fire.

The risks also extend beyond fire. Wood pellet cargoes can produce hazardous atmospheres, including oxygen depletion and carbon monoxide accumulation. This creates additional concerns for personnel conducting inspections, entering cargo spaces or responding to abnormal conditions.

The wider lesson is that effective cargo management must address both the physical condition of the cargo and the atmospheric hazards that may develop during storage and transportation.

What could reduce the risk?

The Nautical Institute highlights several preventive measures based on the USCG’s recommendations, with particular emphasis on moisture protection, storage duration and routine monitoring.

For shipowners, operators and crews, the main considerations include:

• Preventing moisture exposure: Protect wood pellet cargoes from external moisture sources, suspend cargo operations during unsuitable weather and ensure hopper covers or hatch arrangements prevent rainwater ingress.

• Reducing prolonged storage: Coordinate loading, transport and delivery schedules to minimize the time cargo remains stored, particularly aboard barges awaiting onward movement.

• Monitoring cargo temperatures: Conduct routine temperature measurements, using appropriate methods and equipment, to identify abnormal heating before visible smoke develops.

• Recognizing early warning signs: Include cargo deterioration, discoloration, unusual temperatures and other abnormal conditions in routine inspections, with clear procedures for reporting concerns.

• Controlling atmospheric hazards: Consider the potential accumulation of hazardous gases and oxygen depletion when planning cargo-space inspections or entry, following applicable IMSBC Code requirements and enclosed-space entry procedures.

Monitoring and emergency-response arrangements should reflect the properties of the specific cargo. Decisions about ventilation or opening cargo spaces must account for the possibility that introducing oxygen could intensify smoldering combustion.

Source: safety4sea.com