What's Wrong With This Picture?

Each year, fire departments all across the nation spend millions of dollars and man hours working to prevent the loss of life to fires in buildings. Professional fire inspectors carefully walk through businesses and public venues to ensure exits are...


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Each year, fire departments all across the nation spend millions of dollars and man hours working to prevent the loss of life to fires in buildings.

Professional fire inspectors carefully walk through businesses and public venues to ensure exits are clear and easily located, aisles are unobstructed and wide enough, combustibles are not in the way of egress or stacked too high and fire hazards are mitigated. But every year, in communities across the globe, entrepreneurs sell tickets and profit from putting people in corn mazes that break every one of these fire prevention principles. Customers line up and pay to walk into a field of flammable corn leaves grown 12 feet high, with exits blocked or nonexistent aisles that dead end and leave no way out, while campfires often burn on the perimeter of the maze for effect.

The problem

Is there a life-safety hazard in a cornfield maze? Recent research reveals the potential of dry corn to support combustion with surprising results. When green corn is allowed to dry, it takes very little time for the leaves to turn tan in color, which is the point at which they will support combustion. The research involved using the book Standard Fire Behavior Fuel Models, USDA Report RMRS-GTR-153, to categorize cured corn plants as a fuel, just as any other wildland fuel would be. From this book, corn fits into fuel model GR9, “Very High Load, Humid Climate Grass.”

This model indicates an extinction moisture content of 40%, which means it will burn readily when the relative humidity is below 40%. The corn leaves themselves are classified as a “One Hour Fuel,” meaning they can take on and give off their moisture within a one-hour time-lag period. Now, recall from the National Wildfire Coordinating Group (NWCG) course S-190, “Introduction to Wildland Fire Behavior,” that a one-hour fuel is very susceptible to changes in relative humidity. In this case, if the relative humidity is 40% or lower, the corn leaves will give off enough moisture and be ready to burn within one hour.

The categorization as a fuel model GR9 provides the remaining information about fire behavior based on data previously published in Standard Fire Behavior Fuel Models: A Comprehensive Set for Use with Rothermel’s Surface Fire Spread Model (2005) by Joe H. Scott and Robert E. Burgan of the U.S. Department of Agriculture/Forest Service’s Rocky Mountain Research Station (http://www.fs.fed.us/rm/pubs/rmrs_gtr153.pdf).

Ignition causes

So what causes a cornfield to ignite in the first place? This can happen accidentally or as the result of a deliberate act. One accidental ignition was caused by catalytic converter heat when cars were allowed to park in dry corn stalks that had been knocked over to accommodate vehicle parking at a corn maze in Pennsylvania. Another fire was reported to have been maliciously set by a juvenile in a straw bale maze in Ontario in which dozens of people barely escaped injury.

Another problematic practice at corn mazes is the use of campfires for warming and ambiance in cool fall weather. These innocent-looking campfires can provide the ignition source needed to spark a deadly blaze. And one can only imagine the possibilities that exist for an arsonist with the desire to deliberately set fire in a crowded corn maze.

Do we have a corn maze problem?

In the U.S., corn is grown in nearly every state. Determining if your jurisdiction has a potential for cornfield fires is relatively simple. The first question is, when do the corn leaves in your area cure and turn tan? Because the corn maze season runs from late September into December, it is a matter of timing. If the corn in your area stays green through these months, your risk is low. If not, to further evaluate your risk, you can then study the fall weather patterns during these months to get the whole picture.

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