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LOCATION? ADD REFERENCE the graph on the left indicates the rate of spread in chains (66 feet) per hour, with different wind speeds. The graph on the right indicates flame length in feet with different wind speeds. The important facts to glean from the charts are how fast the fire will move through the corn field. From the graph, with a 10-mph midflame wind speed, one could expect 400 chains per hour, or a six-mph, rate of spread. This is equivalent to a person running a 10-minute mile. If the wind speed was just five miles an hour faster, at 15 mph, the rate of spread would double to around 1,000 chains per hour, or 12 mph. This is equivalent to running a five-minute mile. The second graph above shows flame lengths, which in this example would be in excess of 50 feet! Recall from wildland fire behavior the effect of flames pre-heating the fuels ahead of them to multiply the rate of spread and the difficulty in controlling such a firefront.
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.
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).
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.
What are the typical humidity levels, and local wind speeds in your area during these months? As you have learned, humidity is critical because corn leaves will readily ignite when relative humidity levels are 40% and below. If your research shows relative humidity values below 40%, you are at risk for a corn maze fire. Just how serious of a fire will depend on wind speed when the fire starts.
While a six-mph flame spread doesn’t sound menacing at first glance, consider the difficulty of running from a fire through a corrugated field with unmarked exits and smoke obscuring your path. Because most of the paths are dead ends, participants in the corn maze will begin to panic and realize the difficulty of finding their way out. Can we expect the public to escape at the speed of a 10-minute mile?
The complexity of a corn maze can have a dramatic effect on getting out because these mazes are created with the intent to get people disoriented and lost. The size and scope of a corn maze is limited only by the imagination of the designer. While most corn mazes are five to 10 acres in size, some goliaths are being built each year. Adventure Acres corn maze in Bellbrook, OH, outside Dayton, consists of 62 acres of corn maze with 8½ miles of trails. That maze has a length of 1,550 feet and a width of 1,000 feet at the widest end.
Designers pride themselves on reproducing a design into the cornfield, which ultimately creates the maze. Most designs start with a picture or shape, and that design is programmed into a global positioning system. Corn mazes are cut using a GPS device with remarkable accuracy using traditional farming machinery, but some owners use riding lawn mowers to make isle widths smaller and more confining for maze participants.
Fire department response
Egress is not the only problem. The local fire department may have difficulty locating the field because of no physical address, lack of pre-planning and the smoke column laying flat and making the source of the fire difficult to find. It is possible that a large-scale cornfield maze is taking place in your jurisdiction each year, with thousands of guests per day, without your knowledge. Because they are new and part of the agritourism commerce explosion, municipalities and fire districts do not treat them as a regular business, and therefore do not inspect the operation prior to opening day. This opens the door for code violations and does not afford the fire department the opportunity to pre-plan the site.
Responding to a fire in a cornfield may be a common occurrence in some parts of the country; however, responding to a fire at a corn maze is much different. The physical location of the maze may not be readily available to your dispatcher because of the lack of an address or its rural location.
But getting there is only half the battle. Are you prepared to drive your emergency vehicle into a field that appears firm enough to hold the weight of your apparatus? Consider responding with a four-wheel-drive brush engine in addition to a structural engine. The agility of a smaller brush engine may make getting to the fire possible, regardless of the soil conditions.
What about fire attack? Considering the size of a cornfield maze, and the fuel load, would a one-inch grassfire line be adequate or would it be a better choice to stretch 1¾-inch attack lines for knockdown power and stack extra lengths on for long stretches? With fire attack comes the logistics of a water supply. In most areas, calling for water tenders early in the incident could save the day. From the incident command standpoint, how would you address the issue of search and rescue in the corn maze? Would it be appropriate to don self-contained breathing apparatus (SCBA) and enter the maze to perform search and rescue operations? If the decision to send firefighters into the maze was made, careful consideration about accountability must be made to keep track of our own. And if so, what about a rapid intervention team?
Another concern is evacuation – how to coordinate it, how to know when evacuation is complete and where evacuees would seek shelter. Because this event could be a mass-casualty disaster, EMS must be integrated into the initial response plan. If any of these questions are leaving you scratching your head, consider getting a few crews together to discuss this information and brainstorm solutions to these problems.
Solving the maze
How does the fire service move forward and take a proactive stance on this community risk? Although a recent study did not locate any documented loss of life in a corn maze fire, any dedicated firefighter can draw the conclusion that it is not a question of “if,” but of “when.” Some simple steps can assist your department to keep this trend alive.
The purpose of this article is to define the fire risks of a cornfield maze and develop a prevention plan for the hazards associated with cornfield mazes. The fire risks could be intentional or deliberate acts of an arsonist or unintentional causes like a dropped cigarette or a campfire ember that blows into the field. While mitigating these risks may seem straightforward, the real work is implementing a prevention plan for reducing risk that would include a walk through with both suppression and prevention personnel. This two-pronged approach creates unity within the fire department and allows for the best practices of each discipline to come to the surface to prevent loss of life.
• Prevention’s role. The fire inspection is not much different than any other business; addresses posted, egress/ingress clearly identified, extension cords used properly, lighting both operational and emergency type, etc. The emphasis for a corn maze inspection would be to pay particular attention to fire-related activities such as smoking, campfires, use of lanterns at night, vehicle parking and food concessions.
• Fire suppression’s role. During the fire inspection, walk through the operation with your fire prevention representative. This is an opportunity to share information about each other’s role in solving life safety issues in the corn maze. When the fire inspection is over, switch the focus to that of getting apparatus on location and involve your crew with some “what-if” scenarios. Talk about a power line down on the upwind side of the corn maze with a 30-mph wind blowing across 200 people in the corn maze. This should get even the newest firefighter on your crew involved in the conversation.
Some jurisdictions have noticed, others have not. Some fire departments sponsor these events as fund raisers. A few entities have noticed and created awareness programs, but the fact remains that there is work to be done to reduce the risk of a devastating loss of life in the cornfields of America. n
The Applied Research Project on which this article is based, The Fire Risks of a Cornfield Maze by Captain Brian Ashton of the Boise, ID, Fire Department, has received a 2011 Outstanding Research Award from the National Fire Academy. A full copy of the research can be found at“http://www.usfa.fema.gov/pdf/efop/efo46029.pdf” http://www.usfa.fema.gov/pdf/efop/efo46029.pdf.
BRIAN ASHTON is a 20-year veteran of the fire service, serving as a captain with the Boise, ID, Fire Department. Previously, he served with the North Ada County Fire & Rescue District in Garden City, ID. He holds a master’s degree in public administration, a bachelor’s degree in business/human resource management and an associate’s degree in wildfire management. Ashton is an Idaho-certified instructor in wildland firefighting and an adjunct instructor for the College of Idaho’s fire service degree program. He has taught the Incident Command System (ICS) for the Department of Homeland Security since 2007 and is a third-year student in the Executive Fire Officer (EFO) program at the National Fire Academy.