Opening the door provided additional air to a smoldering living-room fire and caused the fire to increase in burning rate and flames to extend out the doorway, resulting in high temperatures and heat flows that melted a hole in the mask. Pressure sensor (brass fitting that was mounted on the face of the headform) is visible through the hole in the lens. Credit: NIST
Melting SCBA facepiece lenses
Published: 31 January, 2012
NIST releases report into ‘what is often considered the weakest component of a firefighter’s ensemble in high heat conditions.’
NIST (National Institute of Standards and Technology) conducted experiments (with the support of the Chicago Fire Department, the Department of Homeland Security, and the U.S. Fire Administration) which demonstrated a range of realistic thermal exposures and environmental conditions that firefighters could be exposed to.
Self-contained breathing apparatus (SCBA) facepieces were exposed to thermal environments from propane-fueled calibration experiments and furnished townhouse fire experiments. Eight facepieces were tested in six different experiments, with three facepiece lenses showing evidence of thermal degradation from the exposure. Maximum exterior lens temperatures were as high as 300 °C (572 °F) in these cases. The environments that caused the failures were identified in an attempt to characterize the thermal performance of SCBA facepieces.
The next step is to identify the exposure limit just before thermal degradation occurs. Data on the limits of the equipment would be valuable information for the fire service to help prevent further injuries and fatalities related to SCBA equipment failure. These fire experiments revealed information on the approximate heat flux and temperature environment that will cause a facepiece lens to degrade, but future experiments will utilize a gas fired radiant panel exposure, which can provide a controlled and repeatable way to generate a uniform heat flux. The heat flux from a radiant panel can be controlled and varied from low heat flux, with intensity just above the flux of sunlight, to a high heat flux representing conditions at the onset of flashover. In future experiments more information on the progression of the degradation can be gathered by recording video of the facepiece lens during the exposure. In addition, the breathing effect can be further studied using a breathing machine to simulate both inhalation and exhalation.
To read the report, click here.
NIST - background
Founded in 1901 and now part of the US Department of Commerce, NIST (National Institute of Standards and Technology) is one of the country’s oldest physical science laboratories. Congress established the agency to remove a major handicap to US industrial competitiveness at the time — a second-rate measurement infrastructure that lagged behind the capabilities of England, Germany, and other economic rivals. Today, NIST measurements support the smallest of technologies—nanoscale devices so tiny that tens of thousands can fit on the end of a single human hair—to the largest and most complex of human-made creations, from earthquake-resistant skyscrapers to wide-body jetliners to global communication networks.