While a fire is a tragedy for any family, they can be particularly devastating for farmers. Fires can damage or destroy a farmer’s buildings, feed, livestock, and machinery, impacting their livelihood. The cost to repair, replace, and/or rebuild after a fire adds up quickly.
Hay is a common cause of fires on farms. While hay can ignite for a variety of reasons, the spontaneous combustion of hay bales are a frequent cause of farm fires that can be minimized with proper curing and storage procedures.
What Causes Spontaneous Hay Fires?
Freshly cut hay is not dead; plant cell respiration continues as the hay cures. Small amounts of heat are released throughout the respiration process, creating ideal conditions for the growth of microorganisms and bacteria, which also produce heat. As hay is cured, the moisture content of the crop decreases until respiration can no longer continue. The cured hay can then be baled safely.
If hay is baled too soon, its increased moisture content will sustain respiration and bacterial activity for longer periods. The interior of moist hay bales can reach 170° Fahrenheit or higher, sometimes increasing at an alarming rate. Under the correct conditions, bales can spontaneously combust when exposed to oxygen.
Reducing the Risk
- Weather conditions can influence the rate at which hay dries. Monitor weather forecasts for ideal conditions prior to scheduling haymaking activities.
- After being cut, hay should be cured to the proper moisture content prior to baling. This is typically 10-15% moisture.
- Conditioning equipment can help speed up the drying process. Fluffing, turning, or spreading the windrows with tedders and hay rakes can also accelerate the curing process.
- Chemical preservatives or drying agents can inhibit bacteria growth and reduce the risk of hay fires.
- Newly stacked hay should be checked frequently for heating. Use a probe and thermometer to take multiple temperature samples from the center of the hay stack. For best results, allow the thermometer to remain undisturbed in the bale for at least 10 minutes.
- Bales should be stored in a dry area that allows air circulation. If stacked outdoors, hay should be elevated off the ground and covered.
- Have an emergency action plan ready. Consider alternative transportation, feed, and housing for yourself, your livestock, and any farm equipment.
- Review your insurance policy to ensure you have adequate coverage, especially if your operation has grown or expanded recently.
Know the Signs
While high internal temperatures can indicate that a fire is imminent, seeing or smelling smoke means that a fire is already present. If you see or smell smoke, do not move the bales, as this can allow more oxygen to feed the fire. Call the fire department immediately, and be sure to include the fire’s exact location on the property. Report any flammable products stored in the area of the fire – fertilizers, gasoline, pesticides, etc – as well as nearby water sources, if known.
- Gay, S. H., Grisso, R., Smith, R., & Swisher, J. M. “Hay Fire Prevention and Control.” Virginia Cooperative Extension.
- Martinson, Kroshona. “Preventing hay fires.” University of Minnesota Extension.
- Prather, Timothy G. “Hay Fires: Prevention and Control.” National Ag Safety Database.