NIST Study Pinpoints Firefighting SCBAs' Vulnerability
The agency conducted fire experiments in vacant but furnished townhouses with results in a report about the damage to facepieces caused by "uncovered temperature and heat flow conditions," it said.
A recent study conducted by the National Institute of Standards and Technology (NIST) and detailed in a U.S. Fire Administration/DHS report is must reading for the fire service because it clarifies why SCBA facepieces can fail, killing or injuring firefighters, according to NIST's Mark Bello, who posted a summary of the findings Dec. 6. The study was conducted to find out why some masks have failed in several SCBA-related firefighter deaths, even when the SCBA was supplying air, he wrote.
In two of four tests, "lenses exhibited bubbling and loss of visual acuity, as well as severe deformation, and, in one case, a hole," the NIST team reported. They studied five facepiece models, each from a different manufacturer and concluded every case of lens damage resulted from temperatures and heat flows beyond the performance limits of polycarbonate, which is the typical lens material for firefighters' SCBAs.
"Our results do not suggest, in any way, that that lens failures are due to the manufacturers," said NIST's Nelson Bryner, a co-author of the report. "All the lenses tested were consistent with requirements specified in standards." Previous efforts to compare real-world fire conditions with the requirements of NFPA standards were hampered by lack of information about the high temperatures and heat flows that actually occur, according to NIST.
The experiments were conducted in two-story townhouses in Bensenville, Ill., with assistance from the Bensenville and Chicago Fire Departments and the federal Bureau of Alcohol, Tobacco and Firearms. "The most devastating damage occurred in a scenario akin to one in which a firefighter would enter a burning living room from a front porch," Bello wrote. "The living room fire smoldered for five minutes after ignition. Opening the front door literally breathed life into the smoldering fire. The rush of heat from the now blazing living room transformed a relatively cool environment on the porch into an inferno. The SCBA lens's exterior surface temperature reached 280 degrees Celsius (536 degrees Fahrenheit), about the midpoint of the range of published polycarbonate melt temperatures. The lens developed a significant hole, according to the NIST report."
He reported that the NIST researchers now want to "identify the exposure limit just before thermal damage occurs."
The "Fire Exposures of Fire Fighter Self-Contained Breathing Apparatus Facepiece Lenses" study is available here.