This past spring and summer the Berks County area experienced wet conditions and producers were challenged with small windows of time to bale hay at proper moisture levels for nutrition and safety. Frequent showers, constant cloudiness, and wet fields increase the risk of putting wet hay away in your barn, which may lead to hot hay or hay fires. Taking a few extra steps during hay season may significantly reduce the possibility of barn and hay fires.
Within the first two to six weeks after baling, hay is still curing, so spontaneous combustion is the most common. When the internal temperature of the hay rises above 140°F, the hay produces heat activated bacteria which, when combined with oxygen, causes spontaneous combustion.
Fires can take place both inside and outside in loose hay, small bales, large bales, or stacks. Wet hay or excessive moisture is the most common cause of hay fires. Stored small hay bales should have moisture content between 18 to 25 percent and large round bales should be lower at 14 to 18 percent. Even if you know you put your hay away dry, hay can become damp due to barn leaks, moisture from the ground, or high humidity. It is best to check your hay regularly. If you detect a distinct caramel odor or a musty smell, your hay is probably heating.
An easy way to check the temperature in the haystack is to insert a thermometer inside a probe to accurately determine the heat level. This can be made with a 10 foot pipe that is hammered together at one end to form a pointed dowel. Drill eight holes in the pipe about three inches above the dowel end. Connect a long rope to the thermometer and insert into the probe. Check hay temperature by inserting the probe from the top of the stack. Leave the probe in the hay for at least 10 minutes.
Watch for the following temperatures:
150°F Entering the Danger Zone.
Check temperature every two hours.
160°F Danger! Stacked hay should be dissembled to allow air flow to cool them down.
175°F Call the Fire Department! Have them onsite before moving the hay.
185°F Hot Spots and Pockets May be Expected. Flames will develop when heating hay comes in
contact with the air.
200°F Critical! Temperature rise is rapid above this point. Hay will almost certainly ignite.
Remove hay with fire department on site.
Caution: Before entering the hay, place long planks or a ladder on top of the stack. Do not walk on the hay itself. Pockets may have already burned out under the top surface. It is a good idea to tie a rope around your waist and have a second person on the other end in a safe location ready to pull you out should the surface of the hay collapse into a fire pocket.
Many farmers sprinkle salt on hay as it is stored, in an effort to prevent hay fires. However, tests have shown that salt has no effect on controlling spontaneous combustion. Dry ice, liquid nitrogen or carbon dioxide gas pumped into the hay will prevent combustion by eliminating the oxygen from the hay mass.
Spontaneous combustion is not an accident. By following good storage practices, not only will spontaneous combustion by avoided, but a higher quality of hay will be obtained.
-Information collected from Cornell University Cooperative Extension, University of Tennessee, and Penn State University
