NTSB: Oily Rags Caused Total Loss of Luxury Yacht

The marine environment takes a toll on coatings, and to keep up with maintenance, most ships' crews use oil-based paints and finishes almost every day that the weather allows. These materials come with an inherent fire risk, the National Transportation Safety Board warned Tuesday, because waste and rags from cleanup can easily combust. For finishes containing linseed oil - a common ingredient in wood finishes - the risk is elevated by the material's tendency to self-heat and ignite. Left alone, a linseed-soaked rag can catch fire without any external source of ignition - as the crew of the yacht Pegasus discovered last year. 

At about 0200 hours on July 15, 2022, a fire broke out aboard the Pegasus at a marina in Gig Harbor, Washington. No one was on board to detect it, and the blaze had about one hour to spread before a bystander noticed and reported it. Another half hour passed before firefighters were able to bring hoses to bear on the blaze. As firefighting went on, Pegasus' stern slipped below, and the bow slowly settled as the boat took on more water. The fire was finally put out at 0430 when the Pegasus' main deck cabin was immersed. 

The wreck was salvaged, and a county fire inspector came aboard to examine the damage. The transom and aft deck were heavily burned, and under a table on the aft deck was a hole burned through into the engine room. Components near the overhead in the engine room were melted, but below they were undamaged, suggesting that the heat came from above. 

The location of the origin of the fire was on the  aft deck, where the owner and his employee had been working the day before the fire. They had been refinishing wood on board the yacht using teak oil, and the employee had taken the towels used to wipe up the excess oil, put them in a plastic bag and set the bag under the table. The teak oil formulation contained linseed oil, and it had a manufacturers' warning about the self-combustion risks of any wastes soaked in the product. 

There were no indications of other possible causes of the fire, and security camera footage from that night showed no signs of human activity. The county fire marshall determined that the oil-soaked rags were the likely cause of the fire, and NTSB agreed. Once the fire started and burned undetected for an hour, NTSB determined, it was unlikely that the yacht could have been saved. The case was very similar to a fire aboard the passenger vessel Safari Spirit in 2012, which likely started when rags soaked in teak oil were laid out to dry and caught fire on a railing. 

NTSB reminded mariners to follow manufacturers' instructions for disposing of oil-based paint and finish wastes, and in particular to avoid piling up or bagging oil-soaked rags, which allows heat to build up and increases the risk of self-ignition.