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Extension > Agriculture > Livestock > Horse > Horse nutrition > Preventing hay fires

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Preventing hay fires

Krishona Martinson, PhD, University of Minnesota

Hay fires that damage or destroy hay, buildings, and livestock cost farmers millions of dollars in building and feed replacement costs, lost revenue, and increased insurance rates. Since 2000, there have been over 900 livestock and poultry barn fires in Minnesota, resulting in over 26 million dollars in damages (Minnesota Fire Incident Reporting System).

Although not specifically tracked by MFIRS, some of these fires have been caused by spontaneous combustion of hay that was baled too wet. Proper moisture at baling is the key to preventing hay fires. Managing the curing process and storage is vital to reducing the risk of hay fires. MOISTURE IS THE KEY. Moisture content of the hay at time of baling is the single biggest hay fire risk factor. Hay baled at less than 15% moisture has a minimal risk of fire (Table 1). As moisture content increases, the risk of dry matter losses and fire increase. Baled hay becomes a potential fire hazard when the interior bale temperature does not decrease. This occurs when heat is created by bacteria respiration. Table 2 lists the effects of internal bale temperature and fire potential.

Maximum temperature is not the only concern with potential hay fire. Rate of temperature increase should also be monitored and considered when addressing a fire risk. If the internal bale temperature is gradually rising, there is usually a minimal risk of fire. However, if a rapid rise in temperature occurs, the risk of fire is high.

Fire is not the only potential threat of wet hay. Hay that is baled too wet can have a significant amount of dry matter loss. Moldy hay is especially dangerous to horses. Ingestion and exposure to mold spores can cause colic, heaves, and other respiratory health issues. Moldy hay is also a health risk for horse owners. Farmer's lung is an allergic reaction associated with inhalation of dust containing spores and dried fungi that are commonly found in moldy hay. Farmers lung can be disabling for people and repeated exposures can cause scarring and fibrosis.

Table 1.Moisture guidelines at time of baling.

Moisture Ranges (%) Comments
<10 Too dry. Hay may be brittle and dusty.
10 - 15 Recommended moisture range. Minimal risk of fire.
16- 20 Could mold unless propionic acid is used, slight risk of fire hazard.
21 - 25 Will likely mold unless propionic acid is used, moderate risk of fire hazard.
>25 Severe heat damage is likely, high risk of fire hazard.

Table 2. The effects of internal bale temperature and fire potential.

Temperature Ranges (F) Comments
< 130 Minimal fire risks.
130 to 140 Minimal fire risk. Continue checking.
150 Moderate fire risk. Check frequently.
175 to 190 Fire is imminent. Call the fire department.
> 190 Use extreme caution. Bales may combust when moved.
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