Close up of burning hay Zbigniew Nowak/Getty Images
FIERY HAY: When hay moisture content is more than 20%, the stored hay will generate more heat than can safely be dissipated, which increases the risk of fire.

Beware of hot hay temperature danger zone

Once hay reaches 150 degrees F, it’s time to take action.

Farmers often know that the hay they are baling is wetter than they'd like, but they are hoping to save a better-quality product versus letting the rain cause it to deteriorate in the field. Unfortunately, moist hay can quickly become hot hay, which can ignite through spontaneous combustion.

Most farmers strive to bale hay that is field-dried to 20% or less in moisture. At this moisture content the baled hay can cure properly and maintain quality. When moisture content is higher than 20%, stored hay will generate more heat than can safely be dissipated into the atmosphere.

As temperatures rise, dangers of spontaneous combustion increase. Farmers need to be diligent in checking their hay, especially if they know they baled hay that was wetter than normal.

Smoldering hay gives off a strong, pungent odor. This odor is an indication that a fire is occurring. If even the slightest smell is present, take temperature readings of the stack.

Reaching inside a hay stack will give an initial clue. If it feels warm or hot to the touch, that's a good indication that problems may exist. Knowing the temperature of the hay is the only real way of determining how serious the potential fire problem is before flames ignite.

Here are some things you should do when the hay gets hot:

125 degrees. No action needed.

150 degrees. Temperatures should be checked twice daily. If possible, stacked hay should be disassembled to allow more air to move around heated bales for cooling.

160 degrees. Temperature should be checked every two hours. If possible, stacked hay should be disassembled to allow more air to move around heated bales for cooling.

175 degrees. Hot spots or fire pockets are likely. If possible, stop all air movement around hay. Alert fire service of a possible hay fire incident.

190 degrees. Remove the hot hay. This should be done with assistance from the fire company, which should be prepared for hay to burst into flames as it contacts fresh air.

Keeping a watchful eye on heating hay can save your barn or storage building. Checking the temperature of hot hay can help you make critical decisions.

If you see the temperature rising near 150 degrees, you might consider moving the hay to a remote location away from any buildings or combustible material.

Use caution when moving heated bales because they can burst into flames when they are exposed to fresh air. Wetting hot bales down before moving them can help control this hazard.

Source: Penn State University, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.
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