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No More Fires!

July 18, 2011

I have personally experienced two fires.  The first, our barn fire of unknown origin in 2001, changed our lives completely; we are no longer dairying.  One of our livelihoods is now making dry hay, both large and small square bales.  The second fire, in 2009, involved about 110 tons of large square bales. The hay was stacked outside, on pallets; we hadn’t even had a chance to cover it yet.  Some teenagers were playing with lighting spots on fire with their smokes (you can imagine what kind of ‘tobacco’ they were smoking), and putting the fires out with their water bottles.  It was a windy day; predictably, it got away from them.  I don’t want anyone to have a fire experience; this is the time of year that spontaneous combustion in hay causes fires.

Hay itself can cause fires if it is too moist when it is baled.  This is the simplified, shortened version of  how hay fires happen:  all bales heat some from respiration in the plant cells, which continues at a low rate (if hay is baled at less than 15% -20% moisture) and eventually ends.  If the moisture level is too high (over 20%), the heat from respiration and the moisture promotes bacterial and mold growth.  The respiration of the bacteria and mold releases more heat into the bale.

The temperature of hay, especially if it was baled at a high moisture concentration, should be checked twice a day for 6 weeks after baling. A simple temperature probe can be made using a 3/4″ diameter pipe.  Drill eight 3/16″ diameter holes about 3″ from one end, then hammer that end together to form a sharp edge.


Check the temperature in the center of the stacked hay.  Do not walk directly on the stacked hay; pockets may have already burned out under the hay surface. Place boards or a ladder on the hay and walk on those.  Drive the probe from the top of the stack into the inner-most bales. Lower a thermometer to the end of the probe with a piece of light wire.  After 10 to 15 minutes, pull the thermometer out and read the temperature.


<130    Continue monitoring temperature twice a day.
130 – 140    Temperature may go up or down. Recheck in a few hours.
150     Temperature will most likely continue to climb. Move the hay to provide air circulation and cooling. If hay is stored inside evacuate any livestock to a safe area and remove hay from building. Monitor temperature every two hours.
≥175    Fire is imminent or present. Call the fire department immediately. Continue probing and monitoring the temperature.
Fire is imminent if interior bale temperatures exceed 175°F and fire is present at temperatures greater than 200°F.
Other symptoms of hot hay or an internal hay fire include a slight caramel or strong burning odor, visible vapor or smoke, a strong musty smell, and/or hay that feels hot to the touch. If any of these symptoms occur, call the fire department immediately.
Let firefighters take control of the situation once they arrive. Do not move hay if signs of fire are present. Moving hay exposes the overheated or smoldering hay to oxygen and may cause the fire to burn uncontrollably.

3 Comments leave one →
  1. September 1, 2011 1:17 pm

    I have heard of a few barn fires in NY state where stored hay got wet from Irene. Something to be on the look out for. Your tips on how to monitor stored hay are excellent!

  2. Kerri Ebert permalink
    July 19, 2011 10:51 am

    Excellent post, Gail. Thanks.

  3. George Cook permalink
    July 18, 2011 4:06 pm

    Nicely done Gail. One little added feature I’ve used is to get a small wad of sheep’s wool, insert it into the upper end of the pipe, then ram that down to the end of the pipe prior to lowering the thermometer. It cushions the bottom and lowers the risk of breaking your thermometer.

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