Firefighters sometimes find themselves fighting blazes in temperatures as high as 500 degrees F (260 degrees C). Firefighter gear and self-contained breathing apparatus can allow firefighters to safely work for a limited time during these conditions. A recently released National Institute of Standards and Technology (NIST) study,* however, reveals that first responders can't rely on their unprotected handheld radios even in routine firefighting situations, much less in higher-temperature fires, where good communications are especially crucial.
The NIST fire engineers tested three representative portable radio models from three different manufacturers in a wind tunnel designed to simulate thermal conditions at three different degrees of intensity that firefighters are equipped to withstand—Thermal Class 1, with a maximum temperature of 212 degrees F (100 degrees C) for 25 minutes; Thermal Class 2, with a maximum temperature of 320 degrees F (160 degrees C) for 15 minutes: and Thermal Class 3, with a maximum temperature of 500 degrees F (260 degrees C) for 5 minutes. Each of the radios tested listed their maximum operating temperatures as only 140 degrees F (60 degrees C).
One radio of the three samples would not transmit or receive after 25 minutes at 212 degrees F though it did begin working after a cooling off period. In another 15-minute experiment at 320 degrees F, one radio went dead within 8.5 minutes. The other two radios suffered significant performance problems from transmission and reception shutdown to signal degradation or fluctuation. None survived the Thermal Class 2 test and cool down period.
Portable radios inside pockets or firefighter turnout gear fared much better. All survived temperature tests at Thermal Class 1 and Thermal Class 2 maximum heats and times. Pocket protected radios also survived Thermal Class 3, but exposed cords, speakers and microphones did not, effectively limiting the radios to Thermal Class 2 electronics. The NIST engineers suggest that small design changes on the speaker/microphones and cords could allow all the protected radios to reach a Thermal Class 3 rating.
NIST conducted the study to evaluate the general performance of portable radios at elevated thermal conditions, to identify shortcomings and to suggest standards for the radios. The results will be used to develop test methods and recommendations that will be submitted to the National Fire Protection Association and other appropriate standards-setting bodies. The NIST study was conducted by the Building and Fire Research Laboratory for the NIST Office of Law Enforcement Standards with funds from the Department of Homeland Security.
*W.D. Davis, M.K. Donnelly and M.J. Selepak. Testing of portable radios in a fire fighting environment. NISTIR 1477. (.pdf file--requires Acrobat Reader, a free download)