Can Hay Catch Fire All By Itself?


Yes. Ironically wet or moist hay, in particular, is more likely to catch fire on its own (spontaneous combustion). This is due to plant reactions and bacterial growth that combine to raise temperatures inside the bales. When packed tightly enough and with enough moisture, hay can spontaneously combust!

When the internal temperature of hay reaches 55C° and above, a chemical reaction can happen where flammable gasses are created that can then ignite due to the rising temperatures.

Typically, the internal temperature of hay can fluctuate as moisture is used up. The first six weeks of bailing is where you see the exaggerated fluctuations. After this, temperatures tend to steady out and become more stable.

What To Look Out For

Heating occurs in the hay when moisture is above 15% and usually reaches a max temperature of 50C° to 55C° with a small risk of spontaneous combustion. Over the course of 15 to 60 days (depending on stack density and storage/weather conditions) temperatures will decline to a safe level.

If hay is stored with a moisture level of 22%, the risk of spontaneous combustion is greatly increased. Not only this but, the quality of the forage will decrease.

Monitor Hay Temperature

Because of the danger and potential forage loss, there is a necessity to monitor the temperature of your hay. Here is a quick guide:

  • At 65C° – check the temperature daily.
  • At 70C° – measure the temperature every 4 hours and inspect the stacks
  • At 80C° – wet hay down, remove it from the barn or dismantle the stack away from other bales and buildings and contact the Fire Department
  • At 85C° – hot spots or pockets may be expected. Flames will most likely develop
  • At 100C° – this is critical – hay will almost certainly ignite

How To Prevent Hay Bursting Into Flames

In the past some farmers were known to sprinkle salt on wet silage, this is to prevent spoilage but will not help prevent spontaneous combustion. However, one way of preventing combustion is to eliminate the oxygen from the hay, this can be done by pumping dry ice, liquid nitrogen or carbon dioxide gas into the hay.

Bailing hay at the right time is also critical. It has to be done on dry and sunny days to avoid excessive moisture for obvious reasons. However, not every farmer takes into account the storage of their hay. The key is control and monitoring. Storing hay indoors where you can regulate temperature, air humidity and ventilation is the best way of preserving your hay and its quality.

If hay is stored outside it can be exposed to changes in the weather such as rainfall, dew, fog, and even lightning. If you are storing hay outside it is crucial that you protect the stack from ground moisture by placing them on a bed of gravel, poles or pallets.

In addition to this, protect your hay by investing in a waterproof cover, combined with protective breathable netting such as Secure Covers. This will protect the bales from any wildlife trying to eat your hay or damage the waterproof cover.

Finally, the waterproof sheet and Secure Covers can be weighted down using Secure Gravel Bags so they don’t move in high winds

Adopting good storage practices will help to avoid spontaneous combustion and ensure better quality hay. Spontaneous combustion is not an accident. By following good storage practices, not only will spontaneous combustion be avoided, but a higher quality of hay will be obtained.

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