Flood-Dampened Hay Poses Serious Fire Threat

Washington State U officials warn farmers of microbial burst.

Published on: Dec 26, 2007

Stored hay dampened by flooding in southwestern Washington poses a serious risk for spontaneous combustion, according to two Washington State University experts..

Moisture both reduces the hay's quality and can create microbial growth and chemical reactions that could result in fire, according to WSU associate crop scientist Steve Fransen and Skagit County Extension Educator Ned Zaugg.

The two have authored an informational paper on the risk, describing how to test for signs of spontaneous combustion and what to do about it.

The Washington State Department of Agriculture is distributing the paper to farmers and ranchers in flood areas. The information is also available on the WSU Extension Web site: ext.wsu.edu.  

Wet hay stimulates microbial growth that produces heat. The heat in turn dries out the surrounding hay surfaces, stimulating more microbial growth. Various types of microbes live and die as the internal bale temperatures climbs.

"Once the bale temperature reaches about 150 degrees Fahrenheit, the hay is on a one-way street going in the wrong direction," says Fransen. "Above that temperature more heat-resistant bacteria start chemical changes that rapidly increase the temperatures to the point of spontaneous combustion. When the bale temperature gets to 150 to 160 degrees, it's time to take immediate action.'

Farmers are urged to watch for early warning signs.

"Watch for steam rising from bale surfaces," says Zaugg. "You may see molds starting to grow on those surfaces. There will also be an acrid hot tobacco odor from the bales."