Unfortunately, many producers probably do not realize how large their losses really are, or that with relatively little effort or expense they could be reduced considerably. Each year there are many reports of hay barns burning, as well as of fires occurring in hay stored outside. Fire is always a concern with hay, but it takes on even greater importance when an expensive barn can be lost in addition to the hay. Fire in stored hay may occur from either external or internal causes. Internally started fires are a result of hay going through an extreme heat.
Heating is a direct result of microorganism activity in hay stored at high moisture levels.
Even if excessive heating does not result in a fire, it will reduce forage quality. Hay that is suspected of being too wet should be stored outside for about three weeks until the danger of combustion due to heating is past. New crop hay should never be placed against dry hay. Bales known to contain, or suspected of containing, excessive moisture can be temporarily loosely stacked outside, then moved inside after the danger of fire is past. If there is a need to check the temperature of hay, it can be done by fitting a sharpened end on a 10-foot section of inch pipe, then driving it into the hay, followed by lowering a thermometer into the pipe.