An accident report issued by the National Transportation Safety Board (NTSB) has found that oily rags were the cause of a fire that sank the 24-metre Fairline motor yacht Pegasus.
The incident occurred in the early hours of the morning on 15 July last year while the yacht was moored at the Peninsula Yacht Basin in Gig Harbor, Washington. An investigation determined that the probable cause of the fire was "spontaneous combustion due to the self-heating of used oil-soaked rags that had been improperly disposed of on the aft deck of the vessel."
Peninsula Yacht Basin security cameras first captured smoke and flames coming from the aft section of Pegasus at 2.04am. In the video, the fire burned for approximately 45 minutes before intensifying and spreading forward. No one was on board at the time, there were no marina staff on the docks overnight and visibility of the vessel from shore was partially obscured by other vessels moored at the facility.
At 3.02am, an hour after the fire is understood to have started, a bystander saw the fire and notified emergency services, but by the time firefighters arrived, the flames had engulfed the aft section of the yacht.
Firefighting efforts lasted over an hour and the flames were fully extinguished around 4.30am when the vessel sank stern-first due to the damage sustained.
The Pierce County Fire Prevention Bureau conducted a post-casualty investigation and the report said the exterior of the stern, swim deck, transom and aft deck had sustained significant fire damage with charring and "mass loss" of the fibreglass components. A dining table and bench seat had been "consumed" by the flames and there had been a significant area of burn through to the compartment space below.
The flybridge also collapsed into the saloon and galley, and combustible materials in both interior spaces had been consumed by the fire. The damage was estimated at $1.5 million and Pegasus was declared a total loss. A yacht docked nearby also sustained minor damage.
The owner of the vessel initially believed that fireworks had landed on the vessel but told investigators that, on the day before the fire, he and a crewmember had been refinishing wood surfaces of the vessel using name-brand teak oil and microfibre towels. The crewmember, after completing the work, wrapped the used towels in new towels, placed them in a plastic bag, and left the bag under the wood table on the aft deck of the yacht before leaving the vessel. The product contained raw linseed oil, a substance known to be a risk for self-heating and spontaneous combustion when soaked in rags.
"Rags soaked with oil-based finishes, which are commonly used for painting and refinishing, pose a fire hazard if stored improperly," the NTSB report said. "Because they generate heat as they dry, oily rags that are piled up, put together in a trash can, or bagged do not allow the heat to escape, creating a high risk for spontaneous combustion. To prevent a fire, users of oil-based products (or any chemical product) should carefully follow the manufacturer’s instructions for cleanup and disposal of rags, steel wool, brushes, and other applicators."
The full accident report can be found here.