Happy Monday, neighbors! Recently the Shrewsbury Hose Company responded to a report of a fire at a house in town. It was originally dispatched as a “mulch fire in the landscape bed,” but when we got there we found a plastic garbage bag on fire. We determined that the flooring refinisher put the wood dust from the sander in a plastic garbage bag and then threw an empty can of mineral spirits in the bag as well. As the bag sat in the warm sun, the wood dust heated up enough to ignite and the ensuing fire spread to a shrub. Luckily a neighbor saw the smoke and reported the fire right away. However, had that bag been inside the garage or behind the house against a deck or other structure, there could have been a disaster.

According to a study by the National Fire Protection Association (NFPA), spontaneous combustion causes around 14,070 fires in the United States each year. Oil-soaked rags are listed among the most common items first ignited to cause the fire, constituting 35% of the items first ignited to cause these destructive fires.

Combustion happens when a material reacts with oxygen and gives off heat. A spark or flame can ignite explosively, i.e., spontaneously, when introduced to an area where certain vapors or fine powders are mixed with air in a certain concentration. Wood floor finishes often have low flash points, which makes them prone to igniting spontaneously.

Sawdust is a material that is prone to spontaneous combustion, and the risk of spontaneous combustion from sawdust increases when doing refinishing work due to the presence of finish and possibly other volatile solvents in the sawdust.

Some risk factors for spontaneous combustion include:

• Oil-based products such as floor finish, sealer, primer, paint shellac, linseed oil, paint thinner, turpentine, mineral spirits and denatured alcohol
• Any wiping cloth, rag, towel, drop cloth, steel wool or piece of work clothing that has come into contact with a solvent-based material. 100% cotton rags are particularly prone to spontaneous combustion
• Warm environments
• Sawdust

How can you prevent these incidents from happening? Here are some tips:

• Safe disposal of your rags and other things that have come into contact with solvent-based products is key. DO NOT simply toss your used rags into a trash can or plastic bucket.
• Spread out your rags to dry so that they can release heat without as much of a risk of catching on fire. The key here is to make sure there is space in between them, so spreading them out is a must––do not ball them up. The finish must be completely cured before final disposal of the rags. Spraying them with water once the solvents on the rags are cured can be taken as an extra, precautionary step before final disposal.
• One of the safest methods of disposing of oil-soaked or solvent-soaked rags is to cover them with water in a closed metal container. You will have to find some way to dispose of the water properly since it will be contaminated, but this is among the safest methods of preventing spontaneous combustion of soaked rags.
• Keep a fire extinguisher handy in case something spontaneously combusts and you catch it in time to put out the fire.
• Ensure that you or your contractor are disposing of construction waste and debris properly and safely.

Please be safe, and know that we're here if you need us.