Beware of hay fires...
Wet hay favors the growth of organisms which generate
heat and can increase hay temperatures up to 150 degrees
F. Once hay heats beyond this point, chemical reactions take
over and can increase temperatures to the point of spontaneous
combustion. With "wet" hay packed tightly in bales and
stacked together in large quantities, fires are very possible.
Whether hay which is in this situation actually starts to burn or not
depends mostly on the size of the stack and the material surrounding
If hay is stacked loose and sufficient cooling occurs
at the same rate as the heat is generated, the hay may simply
caramelize and turn brown or simply mold. However, if there is
enough hay on the outside part of the hot spots to prevent the escape
of heat, and the carbon, nitrogen, oxygen and moisture levels are
right, a fire will eventually occur due to spontaneous combustion.
If you suspect that your hay may be heating up, the
temperature can be measured and monitored by using the following
Drive a pointed 2" pipe into a hay bale and
lower a thermometer on a string down into the pipe. Wait 10-15
minutes for the temperature to stabilize, then pull it out and read
the temperature. Repeat this in several bales. If a
thermometer is not readily available, drive a solid metal rod or
pipe into the center of the bale and after 15-20 minutes withdraw
the rod. If it is too hot to hold in your hand, the situation
is critical. The temperature should be determined and
appropriate action taken.
Actions to take...
If temperatures are below 140 degrees F there is
not any danger, unless it is early in the process.
When the temperature is between 140-160 degrees F,
check bales daily
If temperatures rise above 160 degrees F, check
every 2-3 hours and prepare to move the hay from the building and
spread out so that air can get around the bales.
If the temperature reaches 180 degrees F, notify
the fire department, insurance company (if the building is
insured) and remove all equipment and/on animals from the
area. With fire equipment on hand (not just an
extinguisher), remove bales to the outside and do not stack.
Place in rows for easy access. During removal, be alert for
burned out cavities. Also, hay under these conditions may
flame up as fresh air strikes it or smolder in a pile for weeks.
If bales ignite, soak with water and force some
water in the center of the bales.
If the bales do not ignite, try to save the hay by
allowing the bales to simply cool down.
Continue to monitor the internal temperature of
the bales. The hay may be put back in the building after the
temperatures drop below 100 degrees F.
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