Inside a small room, a fierce fire blazes. Ribbons of heat cascade through the doorway as the temperature builds to 2,000 degrees Fahrenheit. Outside, at the edge of peril, is a figure fully outfitted in firefighter protective gear. It draws closer, hesitates, then enters the room and disappears into the flames.
But this fire—from ignition to extinguishment—is under the complete control of researchers. So, too, is the mannequin thrust into the inferno. The fiery scenario has been carefully planned, designed, and calibrated by WPI’s Center for Firesafety Studies to test newly designed firefighter clothing for the U.S. Navy’s Clothing and Textile Research Facility located at the U.S. Army Soldier Systems Center in Natick, Mass.
The fire test simulator, or burn chamber, is located at Alden Research Laboratory in nearby Holden. The chamber and its equipment were built by WPI students in 2001; inside, scientists and students can simulate a variety of fire scenarios—from a blazing bedroom to a brush fire.
“This is a good example of what WPI’s educational program makes possible,” says Jonathan Barnett, professor of fire protection engineering, the lab’s director, and the principal investigator. “Students worked together to build it, and students help run it.”
The 10-by-15-foot steel-framed chamber sits in the middle of a cavernous warehouse; double doors on either end stand open. Occupying about one-third of the metal grid floor are eight metal boxes filled with sand. These are the burners; vaporized propane feeds through from the bottom of the boxes, as on a gas stove. The burners’ configuration can easily be changed to imitate a wide range of fires more realistically than has previously been possible, according to Barnett.
The mannequin is part of the test equipment as well. Hanging from a metal track and propelled by remote control, it can do everything from standing near the flames to zipping through at speeds ranging from a half-foot to two feet per second. Researchers measure heat flux from 40 specially designed copper slug calorimeters—sensors that act as surrogate skin—that are evenly distributed around the mannequin. The measurements indicate whether a firefighter would have suffered skin burns while wearing the protective gear and, if so, the severity and locations of those burns.
Though a handful of other laboratories, such as those at DuPont and North Carolina State University, also test firefighter clothing using instrumented mannequins, they can produce only flash fire conditions in which flames shoot out of walls on four sides, engulfing the mannequins.
“But, realistically, a firefighter’s more likely to encounter heated or super-heated atmospheres, rather than direct flames during routine activities,” says Jonathan Martin ’05, who works in WPI’s burn lab.
What a firefighter wears to a fire is just as important as putting the fire out
Burns to the lower extremities, visible on a tested firefighter’s suit (above), register as torso burns via copper slug skin calorimeters on the mannequin (below). The suit is made from polybenzimidazole (PBI), a material used in most firefighters’ suits. “Part of the reason for the extent of these burns,” says Jay Kramarczyk ’04, lab assistant in WPI’s burn chamber, “is that the scenario the suit is exposed to is not practical for a human to endure. In the lab we are given the unique opportunity to expose materials to situations that go far beyond what the wearer of the suit would experience. By designing suits that are far more capable than they need to be, we are assured that they will also perform under normal circumstances.”
Protective clothing has come a long way from the days when firefighters stormed into blazing buildings wearing street clothes. Leather helmets were available by the late 1700s, but it took a century before coats and pants made of rubberized cotton were introduced. These provided no fire protection; they simply kept firefighters dry. A breathing apparatus completed the ensemble by 1908.
“There were no standards for protective clothing until the NFPA [National Fire Protection Association] developed them,” notes Harry Winer, an engineer and protective clothing designer with the U.S. Navy’s Clothing and Textile Research Facility, who attends the burn lab tests on the new garments with engineer Richard Wojtaszek.
But even NFPA standards are based on bench experiments. “Characteristics like the type of fabric, its density, its heat conductivity, and its moisture content all translate into conductive points within the fabric,” says Wojtaszek. “We need the realistic tests done at WPI to see how new fabric reacts and protects.”
Suit of the future
WPI students don their own protective gear before performing a fire chamber test. For this test, the mannequin “stands” two feet from the blaze for 30 seconds as heat pulsates through the chamber openings. Lab assistant Jay Kramarczyk ’04 points the remote at the mannequin, guiding it to the doorway, and then into the chamber at one end and out the other.
By the end of the test, the students are sweaty and their faces are smudged with soot. Analyzing the data from the calorimeters, laboratory computers determine whether the mannequin’s exposure to heat over time would have produced first-, second-, or third-degree burns, or no burns at all. Skin temperature must equal or exceed 44 degrees C (111 degrees F) to burn.
In this test, the mannequin’s outfit has come through the chamber unscathed; a heat sensor analysis detects no skin burns. This would have been one well-protected firefighter.
Winer and Wojtaszek are pleased. The Navy’s new suit, made from highly flame- and heat-resistant zylon and aramid, apparently works well. The engineers expect to see this gear aboard naval vessels by 2006; it will take another year or two for the suit to filter out to civilian fire departments.
Barnett says he would like to see that happen. Chemical and fire burns accounted for 9 percent of firefighter injuries on the fire ground in 2002, according to the NFPA. Between 1977 and 2003, burns caused 8 percent of on-the-scene firefighter deaths. “My goal,” says Barnett, “is for this research to reach the civilian population as soon as possible.”email@example.com
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Last modified: Jan 25, 2005, 15:02 EST