Preventing Spontaneous Combustion Hazards

Knowing how to prevent fires caused by spontaneous combustion is a key aspect of maintaining a safe workplace. Several conditions, including the improper storage or disposal of combustible materials, can create conditions for this process to occur. By taking steps to mitigate this risk, you can help protect individuals at the worksite and safeguard property.

Causes of Spontaneous Combustion

Spontaneous combustion happens when objects increase in temperature without an external heat source, eventually leading to autoignition. Combustible materials can self-heat through chemical or biological processes like oxidation or bacterial fermentation. Factors that can contribute to the likelihood of spontaneous combustion occurring include:

• Improperly storing or disposing of combustible materials (e.g., placing them in areas with poor ventilation)
• High ambient temperatures combined with dry conditions
• The presence of moisture and air
• High oxygen availability

Materials that may be prone to spontaneous combustion include:

• Oily or stain-soaked rags, fabric, towels and linens
• Oil-based paints
• Seed oil (e.g., linseed oil) and products containing seed oil
• Coal, charcoal and peat
• Sawdust and woodchips
• Hay, straw and compost
  

How to Prevent Spontaneous Combustion Hazards

Strategies to address spontaneous combustion risks at a worksite include the following:

• Attend safety presentations about spontaneous combustion and learn how to avoid conditions that may facilitate it.
• Follow proper disposal procedures, including using receptacles rated for flammable materials.
• Thoroughly dry oily rags on a nonflammable surface before disposing of them. They may also be immersed in water before being dried and follow local laws that may regulate the disposal of the rags and oily water.
• Monitor combustible materials to ensure they are not heating up.
• Store rags in a metal container with a tight-fitting lid to prevent oxidation.
• Do not dispose of rags in cardboard boxes, trash bins or debris piles.
• Familiarize yourself with Safety Data Sheets if you work with flammable materials.
• Utilize noncombustible solvents or water-based materials when possible.
• Keep compost, leaf piles, mulch and other materials at risk of spontaneous combustion away from buildings and structures.
• Avoid the stacking or piling of combustible materials in a manner that can trap heat. Materials susceptible to spontaneous combustion should be appropriately kept in a well-ventilated area.

Emergency Response if Spontaneous Combustion Occurs

Spontaneous combustion can still take place despite efforts to prevent it, but there are steps you can take to be prepared if it happens. Actions to consider include:

• Know and follow your company’s fire response plan, emergency response plan and other emergency response protocols.
• Participate in fire drills to know how to evacuate safely.
• Know the locations of evacuation routes.

Conclusion

Spontaneous combustion is a serious hazard that could cause severe injuries or property damage at your job. Taking action to address this exposure can help improve safety and prevent losses.

Contact your supervisor for more information.

This Safety Matters is for general informational purposes only and is not intended to be an exhaustive source of information or medical or legal advice. © 2025 Zywave, Inc. All rights reserved.