BY MARVIN A. SALZENSTEIN, PE, AND ROBERT J. STANIS
In December1994, a fire started in the gymnasium of a large high school in the Midwest and spread rapidly, resulting in a multimillion-dollar loss before the fire was brought under control. Litigation followed, which brought out many theories of the fire experts involved relative to the fire’s origin and, more importantly, its rapid spread.
The gym was a two-story structure that included on one side a mezzanine in which lesser gym activities could be conducted. A retractable wood curtain wall divided the mezzanine gym from the main floor. Telescoping benches were stacked up against the wall on the main floor as well as on the mezzanine. During basketball tournaments, the curtain wall was folded back, and the telescoping benches were pulled away from the wall downstairs on the main floor and upstairs as needed in the mezzanine, providing seating for more than a thousand visitors. At the time of the fire, the benches were stored against the wall, and the curtain wall closed off the mezzanine from the main gym.
The mezzanine gym was set up for gymnastic exercises. Polyurethane foam mats were spread out on the floor, and a stack of mats, some five feet high, were stored near the wall. There was no student activity in this small gym at the time of the fire.
The stacked bleachers were constructed largely of rigid foam polyethylene; the seating and metal and wood materials provided the structure and foot walks, respectively.
The gymnasium was in the process of being retrofitted with an automatic wet pipe sprinkler fire extinguishing system that was being installed following a small fire in the same mezzanine area some 18 months before. At the time of the subject fire, the extinguishing system had not yet been hooked up to the water supply.
CHRONOLOGY OF THE FIRE
The fire was first discovered at about 2:40 p.m. by some construction workers, who saw smoke coming from the enclosed mezzanine gym. When they went inside, they found the stack of exercise mats burning; they attempted to put out the fire with two small, multipurpose dry chemical extinguishers. The flames, however, continued to rise. the workers retreated and sounded the alarm. The source of ignition was never determined but was concluded to be incendiary in nature.
At 2:44 p.m., two smoke detectors sounded the school building alarm, but an automatic tape dialer to the fire department did not function. At 2:51 p.m., the fire department received telephone notice of the fire. The first truck arrived at the scene at 2:55 p.m. The fire was finally brought under control by 3:30 p.m., but not before the entire gym was extensively damaged.
Witnesses who entered the mezzanine gym shortly after the fire was discovered saw flames shooting up from the burning stack of mats and continuing up the wall to the overhead drop ceiling. The wood curtain wall was burning, and flames were moving horizontally across the exercise mats on the floor toward the bleachers. The foam-plastic bleachers subsequently ignited and burned completely except for the metal structural portions. Thankfully, no students were injured. All persons were safely evacuated in an orderly fashion during the early stages of the fire.
INVESTIGATION FINDINGS
The investigation of the fire and its circumstances followed. Many contributing issues were raised and are summarized as follows:
Although the origin of the fire was clearly established, the ignition source was not. Authorities deemed the fire incendiary in nature; the person responsible was unknown.
An automatic sprinkler system had not been completely installed and lacked the necessary water supply.
There was a seven-minute delay in signaling the nearby fire department. A duct smoke detector transmitted an alarm to the main panel at the school, but the alarm did not arrive at the fire department in an intelligible manner.
Two of the nearby fire hydrants on the street did not operate, further delaying firefighting activity. Tanker truck water was initially used.
The retractable wood curtain wall enclosing the mezzanine had an excessive flame spread rating. This allowed the mezzanine fire to quickly breach the wall and spread to the main gymnasium.
The stacked exercise mats and the mats lying on the mezzanine gym floor contributed to the rapid spread of the fire. The mats were constructed of low-density polyurethane and polyethylene foams, covered with a low pile plush carpet; none were fire retardant.
The high-density structural foam seating of the bleachers contributed to rapid flame spread and fuel for the fire, once ignited by the mat fires on the floor.
The ensuing fire breached the gymnasium ceiling and roof before the fire department was able to bring it under control.
The insurance company, on behalf of the high school, filed suit for damages against the manufacturers of the exercise mats and the bleacher seating, respectively. The primary claim against these defendants was that the materials of construction were hazardous with respect to rapid flame spread, fuel contribution, and failure to warn.
An expert for the plaintiff conducted a full-scale, closed-room test of the bleachers. This room was equipped with a large canopy ventilation hood and instrumentation to measure heat-release rates (HRR). The stacked assembly of bleachers was set on fire with a 30-pound wood crib, which, in turn, was ignited by wood excelsior and alcohol. Peak temperatures of some 2,000°F were reached in about seven minutes. The peak heat release rate occurred at about the same time, just under four megawatts (MW). The rate of heat release was described as “ultra fast.” No test was conducted on comparable wood telescoping bleachers.
The ultimate conclusion was that the structural foam-plastic material was deemed too hazardous because of flame spread, heat release, and fuel load. Fire retardant materials should have been employed; adequate warnings to identify the fire hazards (flame spread/fuel contribution) were needed; wood instead of plastic foam would have made the product reasonably safe.
With respect to the flexible-foam plastic mats, this same expert concluded that this product likewise was a severe fire hazard in that it is supplied to the user without adequate warning. Further, other flexible foam products with superior fire resistant properties were available. Although this expert conducted no fire test on the mats, other parties did.
FIRE DEPARTMENT TESTING
The fire department conducted “open bin” fire testing on the stacked mats and found that a few sheets of newspaper kindling were enough to quickly bring the mats to a rapidly burning state. Another expert had a stack of polyurethane slabs similar to the stacked mats ignited with three wood matches embedded in the surface. The fire developed rapidly, consuming some 400 pounds of foam slabs in about three minutes. This expert concluded that the stacked mats in the gym likely had an HRR of more than five MW. (Note: A burning Christmas tree has a maximum HRR of about 0.65 MW.) Additional tests were conducted on the ease of ignition using methenamine pills for timed burning. This test demonstrated the ease of ignition with the flame front expanding radially and burning vigorously.
This expert concluded that the gym mats were unreasonably dangerous because of the hazardous fire properties and the failure to warn the user about these hazards.
Other experts refuted some of the conclusions. In particular, the claim that wooden bleachers would be safer than the structural foam-plastic material was contradicted by the Bradford, England, soccer stadium fire of 1985, which resulted in 56 fatalities. The fire occurred in the main grandstand, which had an occupancy of some 5,000 people. Wood bleacher seats and flooring were in the portion of the grandstand where the fire began. The entire 290- by 55-foot grandstand was covered with a double-peaked wood roof.
The stadium fire apparently started under the grandstand, most likely from accumulated trash and discarded smoking materials. The fire continued to grow, initially slowly, but then took off rapidly to where the entire grandstand was involved in less than five minutes. Because the sporting event was being televised, there was a perfect record of flame travel and activities with respect to time, as cameramen memorialized the ensuing fire.
Another engineering expert opined that even if the fire extinguishing system had been connected to a water supply, the system offered inadequate coverage and would not have been able to handle the resulting fire. Connection of the water supply was impractical because renovation underway would have made the cost excessive. The sprinkler system was designed for a “light hazard”; the fuel load and HHR of the mats and bleachers required a greater design density (gpm/square feet).
The case went to trial in October 1997 with only the manufacturer of the bleacher seats as a defendant. The mat manufacturer settled with the plaintiff a few weeks before trial, leaving the liability and the bulk of the damages against the only remaining defendant to be determined by a jury. After more than two weeks of trial, the jury found the bleacher manufacturer not guilty, ending a three-year investigation that cost tens of thousands of dollars for fire experts and testing.
Fire investigators often consider the ever-increasing use of modern, plastic construction materials during their evaluation of fire scenes. The impact of these fuel materials on the overall spread of fire can adversely affect reasonable levels of fire protection and may also influence life-safety decisions. Fire inspection and code enforcement personnel should address the potential risks that these materials can pose in any occupancy by applying established fire protection code requirements, with due consideration of the specific manufacturers’ fire performance ratings for plastic products and building materials. ■
MARVIN A. SALZENSTEIN, PE, is chairman and principal consulting engineer at Polytechnic Inc., in Lincolnwood, Illinois, which provides safety, testing, and forensic engineering services. He has a B.S. in mechanical engineering from the Illinois Institute of Technology and did postgraduate work in technical optics at the University of London.
ROBERT J. STANIS is project/senior consulting engineer at Polytechnic Inc. He has a B.S. in engineering (chemistry major) from the University of Illinois.
