Preventing Field Fires

This article was written by Mark Hanna, ISUEO Ag Engineer, & Clarke McGrath, ISUEO Field Agronomist & Firefighter for Harlan Fire Department. 


Field/Combine Fire Prevention

Mark Hanna, ISUEO Ag Engineer

Clarke McGrath, ISUEO Field Agronomist; Harlan Fire Department, Firefighter

It’s always difficult to forecast weather, but if dry field conditions persist, potential for combine and field fires this fall will increase. A high-temperature source in the engine area or an overheated bearing can ignite dry plant material. 

Warm, dry winds rapidly dry plant materials. With potential for an earlier maturing crop and resulting early harvest, air temperatures will likely be warmer than during typical harvest conditions. Farmers in northwest Iowa experienced a greater than average number of harvest fires during 2011. A recent study by South Dakota State University ag engineers found an average of nearly seven combine fires per county in nine northwest Iowa counties. Although air temperatures were warm and relative humidity was low during much of early harvest, most fires occurred on days with wind speeds averaging 15 mph and occasional gusts of 25 to 30 mph. This suggests that not only should combine operators be careful when field conditions are dry and air conditions are warm, they should be extra vigilant during windy periods. 

During harvest periods with increased potential, fires cause millions of dollars in property damage in Iowa, including loss of machinery, crops and time. Injuries to farm workers and firefighters are also an unfortunate outcome in some instances.

Modern, high-productivity combines are powerful machines; power means heat. Fire cannot start without heat and fuel. You cannot remove the heat from the engine, hydraulics and other hard-working systems, but you can remove the fuel source by keeping your combine clean.

Prevention is a key to avoiding problems; here are some tips:

  • Keep the machine clean, particularly around the engine and engine compartment. Use a high pressure washer or compressed air to remove caked-on oil, grease and crop residue.
  • Check coolant and oil levels daily.
  • Check the pressurized oil supply line to the turbocharger for wear areas that rub and may start an oil leak.
  • Frequently blow leaves, chaff and plant material from the engine area with compressed air or a portable leaf blower. Doing this one last time at night is better than in the morning when dew may make it harder to blow residues off.
  • Remove plant materials wrapped on or near bearings, belts or other moving parts. 
  • Examine exhaust or hot bearing surfaces. Repair leaking fuel or oil hoses, fittings or metal lines immediately.
  • Inspect and clean ledges or recessed areas near fuel tanks and lines. 
  • Prior to fueling, wait 15 minutes to reduce the risk of a spill volatilizing and igniting.

In case of fire, call 911 first, and then attack with fire extinguishers if it is safe to do so.A fire can double in size in less than a minute; burning embers blown downwind can spread the fire well beyond the control of your fire extinguishers in just seconds.

 Two ABC-type fire extinguishers are recommended: a smaller 10-pound unit in the cab and a larger 20-pound extinguisher at ground level on the combine. Invert and shake the extinguishers once or twice a season to ensure machine vibrations don’t compact the powder inside. A shovel to throw dirt can also help. 

Fires may start from plant materials that have smoldered unnoticed for 15 to 30 minutes or more. The ignition source for field fires may have been the earlier passing of a truck, tractor or combine. Flames aren’t apparent until additional oxygen is supplied, perhaps by a gust of wind. Harvest crews and neighbors may want to discuss a plan for emergency tillage of a fire break should that option become advisable. Keep in mind that personal safety is more important than property loss. 

With current prospects for an early, dry harvest, fire prevention measures will be more important than usual. 


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