Wet hay molds quickly and heats. Spontaneous combustion can occur within two or three days. Therefore, special care is needed if hay becomes wet.
University of Missouri Extension specialists recommend that wet hay be spread out quickly to dry and turned often as it is drying. Hay storage areas should be monitored often for pungent odors, hot damp areas on the stack, and emission of water vapors and other signs of heating.
Knowing the temperature of the hay is important. To check the stack's temperature, drive a sharp-pointed pipe down into the hay, lower a thermometer inside the pipe, and leave it there for about 20 minutes. Make the reading quickly when the thermometer is removed.
Use the following guidelines to determine the danger zone:
Caution: When working with hay that is dangerously overheated, do not allow workers to enter the hay storage area alone. Workers should wear a full body safety harness attached to suitable rescue rope so that they may be pulled to safety quickly if overcome by unforeseen, harmful conditions. Protect lungs with a respirator rated for mold when working in potentially moldy conditions, and be aware that carbon dioxide, which is odorless and colorless, can quickly cause unconsciousness and death. Filter and cartridge respirators do not protect a worker from carbon dioxide. Only a breathing apparatus that supplies oxygen can protect from the danger of concentrations of carbon dioxide. Be aware that fire pockets may exist under the surface. Use long planks across the top of the hay to reduce the chance of a sudden drop into spoiled or smoldering hay.
For more information, contact the University of Missouri Extension center in your county, or call 573-882-7477.
William W. Casady
CasadyW@missouri.edu
Extension Associate Professor and Professional Engineer
Commercial Agriculture Program Cropping Systems Engineer
University of Missouri-Columbia
Reviewed 12/12/07
