What Is Spontaneous Combustion and How Can You Prevent It?

How to prevent spontaneous combustion | City Floor Supply

We had an unfortunate brush with spontaneous combustion when a devastating fire leveled our old warehouse in 2015, so we continue to strive towards educating contractors and other professionals in our field about the very real threat that spontaneous combustion poses to our equipment, our property, and our very livelihood. Click here to read our blog series about the lessons we’ve learned in the wake of the fire.

Hardwood flooring contractors make up one group of people which is especially susceptible to experiencing spontaneous combustion.

This is due to the sheer nature of the materials that flooring contractors work with, namely solvents with low flash points, such as hardwood floor finishes, as well as sawdust from refinished floors.

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What is spontaneous combustion, and how does it happen?

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. You can read the NFPA study here.

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 another 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 
Risk factors for spontaneous combustion | City Floor Supply

Looking at the above list, it is clear that these are things that hardwood floor contractors deal with on each and every jobsite––it’s the nature of the job. The best way to prevent spontaneous combustion from taking hold in your vehicle, jobsite, or in your shop is to know the protocol for handling and disposing of these potentially hazardous materials.

How to prevent spontaneous combustion:

    • When sanding floors, especially refinished floors, make sure to empty the bags of sawdust often. Don’t operate your sander when the dust bag is more than halfway full, and never leave the sander with dust in the bag at the jobsite, in your shop, or in your vehicle. Take it from Josh Vause, who shared a harrowing story in a comment on a Wood Floor Business article on this same topic. Josh found a bag full of dust right next to the client’s garage right as it began to combust:

      This past Sept. I had an employee that didn’t empty the big machines bag after a fine sanding and laid the bag next to the exterior wall of the homes garage. Luckily, I had to go out to my trailer to grab buffing paper. I could smell smoke when I exited the trailer and the smell intensified as I walked down the ramp. I nearly freaked out because I knew what it was instantly. I grabbed the dust bag and when I picked it up, the air sucked in through a hole, that had been burned into the bag. I ran with the bag to the grass where the sprinklers were on and threw the bag out into the yard. As I threw the bag, the thing went into flames!! It literally smoldered into a tiny pile of burned dust and canvas. Thank God I found that thing, probably would have burned down the garage…”

  • 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 in your vehicle in case something spontaneously combusts and you catch it in time to put out the fire.

Be aware and be vigilant

Half the battle against spontaneous combustion is knowing what you are up against, and knowing exactly what the risk factors are.

With some careful maintenance and vigilance, you can prevent spontaneous combustion from claiming your equipment or worse.

Have you ever had an encounter with spontaneous combustion? Let us know in the comments.

2 thoughts on “What Is Spontaneous Combustion and How Can You Prevent It?

  1. Tim

    I just had an experience. Small trash can with saw dust and empty spray paint cans. Been doing this a long time never knowing of the risk. Thank God, the sprinkler system in the garage activated and put the fire out. The fire occurred in the garage of my apartment and could have resulted in a much worse ending.


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