By: Edward L. Blais, JD, CIC 

When most of us think of fire hazards we worry about stoves being left on, faulty wiring, or a space heater too close to the curtains. That pile of oily rags? Not so much. 

But those oily rags could become deadly due to a chemical process called spontaneous combustion, in which materials catch fire in the absence of a spark or flame. All it takes is high internal temperatures and exposure to oxygen. Materials like oily rags, stored bays of hale, and large compost, mulch, manure or leaf piles can all self-combust. 

Often, this process takes place overnight or after hours. Every year, there are an estimated 14,070 spontaneous combustion fires, according to the National Fire Protection Association (NFPA). Of these, about half were on residential properties. The most common area of origin in home structure fires were garages and oily rags were the most common cause, according to the NFPA. 

Follow these simple prevention tips to make sure this doesn’t happen to your home or your business: 

Oily rags

  • DON’T put rags soaked in oil or another flammable material on top of each other in piles or containers like cardboard or wooden boxes. 
  • DO lay oily rags out to dry in a well-ventilated area that is cool. Spreading them out on concrete is ideal. Make sure they are weighed down so they don’t blow away. Keep them away from buildings and out of sunlight. After the rags have dried you can store them in a metal container with a tight lid. Fill the container with water and detergent to prevent spontaneous combustion. 

Piles of hay, compost, mulch, manure, and leaves

  • smoldering mulch pilesDON’T store hay, compost, mulch, manure, and leaves in large piles near buildings. 
  • DON’T move hay to a storage facility while it’s still damp. 
  • DO store hay, compost, mulch, manure, and leaves in small piles away from structures. The smaller piles will ensure air circulates and the internal heat dissipates. 
  • DO move completely dried hay to storage facilities that are well-ventilated. 

Gasoline, kerosene, and other flammable liquids

  • DON’T store gasoline and flammable liquids in containers not designed for that use. 
  • DON’T use any flammable liquids for cleaning or treating grease. 
  • DO store gasoline and flammable liquids in their original containers or containers meant for that use. Make sure the container has a tight cap to prevent fumes from escaping. 
  • DO dry out your clothes if they have any oily liquids on them. You can wash them after they have dried out. 

While spontaneous combustion may seem unlikely, it is a real threat. By taking these steps, you will ensure you aren’t caught off guard. 

(Tips adapted from the Selective Insurance Group, the NFPA, and the National Park Service.)