This manual was prepared to inform Tennessee farmers and firefighters about the causes, prevention and control of hay fires. However, the University of Tennessee Agricultural Extension Service will not be responsible for accidents, injuries or any other losses resulting from the application of practices described in this publication. This is unfortunate, because proper harvesting and storage practices can practically eliminate hay fires. Hay fires usually occur within six weeks of baling, but they may occur in hay several years old.
Fire can occur in loose hay, small bales, large bales or in stacks.
The fires can occur in hay stored inside as well as in hay stored outside. Regardless of when or where the fires occur, the most common cause is excessive moisture. Freshly cut forage materials are not dead. Some respiration continues and a very small amount of heat is produced. This heat generated by respiration is probably of little consequence except that it may help provide proper conditions for growth of bacteria.