Spontaneous Combustion
Some materials can heat up and burst into flames without any spark or flame. The heat comes from slow chemical reactions that cannot escape. Fires often start hours after work ends, when no one is around.
- Painters
- Landscapers
- Homeowners
How it happens
Certain materials react with oxygen and give off heat. If the heat is trapped, such as in a pile of rags, the temperature climbs until the material ignites. Insulation, bulk and moisture speed up the process.
Common sources
- Rags and papers soaked in drying oils: linseed oil, tung oil, some wood stains and varnishes, oil-based paints, and some cooking oils and cleaners. See Oily Rags.
- Mulch, compost, wood chips, sawdust and manure in large piles.
- Hay and grain stored damp.
- Coal and some metal powders, and oily sawdust in shops.
- Towels and laundry with cooking or massage oils, dried in dryers. See Dryer Fires & Lint.
- Chemicals that react together; read labels and SDSs.
Prevention
- Put oily rags in an approved oily waste can with a tight lid, or lay them flat outdoors to dry in a safe place, away from buildings.
- You can also submerge them in water in a metal container with a lid, then dispose of them as local rules say.
- Never wad or pile used rags, or leave them in a pocket, bucket or plastic bag.
- Empty oily waste cans daily and remove them from buildings at the end of the shift.
- Keep large mulch and compost piles small enough to stay cool (often under 4 to 5 feet), keep them away from buildings and turn them or monitor temperature.
- Store hay dry. Check temperature with a probe if it feels hot or smells like burning or tobacco.
- Keep drying-oil products closed and dispose of leftover materials as hazardous waste.
Signs and response
- Warning signs include heat, a hot or burnt smell, steam, a sweet or musty odor, or smoke from a pile
- Do not poke or dig in a smoldering pile; air may make it burst into flame
- Call the fire department and keep people away
- Report any rags or piles that feel warm and move them outdoors only if you can do so safely
Standards & references
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