Cranking up the heat on firefighters’ radios
How much heat can a firefighter’s radio take? Thanks to researchers, the fire service is starting to find out. But whether manufacturers ultimately will be forced to redesign their products is debatable at this point.
As part of a new standard, the electronic safety equipment committee of the National Fire Protection Association (NFPA) will spell out how portable radios, thermal imaging cameras, location devices and other systems should function in the face of extreme heat and other conditions a firefighter encounters.
“Within that standard, there will be a number of performance metrics and testing protocols that will be applicable to radios,” said Nelson Bryner, who leads a unit of the National Institute of Technology and Standards’ (NIST) Fire Research Laboratory and is a member of the NFPA committee working on the standard.
Last year, NIST conducted two studies to provide data for the NFPA committee, focusing particularly on how extreme heat affects electronic equipment. In the first study, researchers developed a system to classify different thermal conditions (see table), based on temperature, length of exposure and flux (rate of heat transfer). They also constructed a test environment, the Fire Equipment Evaluator, and used it to test the heat resistance of personal alert safety system devices.
The second study focused on hand-held portable radios. Researchers observed how three models, from three different manufacturers, performed when exposed to conditions defined by the first three thermal classes. They tested the radios in two ways: exposed directly to the air and tucked inside the chest pocket of a firefighter’s turnout gear.
“It was apparent that none of the electronic equipment that firefighters use had been standardized at temperatures that firefighters encounter,” said William Davis, a physicist with NIST’s Integrated Performance Assessment Group, who led the studies. The researchers hoped to provide the scientific basis for equipment standards, he said.
The tests proved a challenge for the unprotected radios. Under Thermal Class I conditions, two of the radios performed well throughout three tests, but the third stopped transmitting during its second exposure and didn’t recover when it cooled down. All three radios either malfunctioned or died completely under Class II conditions.
But protected inside a turnout coat pocket, the same radio models fared much better, continuing to work even in Class III conditions. During one exposure, a radio suffered some melting and its antenna became slightly deformed, and another radio’s antenna curved to approximately 90°. But all three continued to transmit and receive.
“The fact that it looks like we can get these things to behave at Thermal Class III criteria is very, very nice,” Davis said.
It’s so nice, in fact, that in the minds of some, there may be no need to make portable radios any more heat resistant.
“Most firefighters do not wear their portable radios on the outside,” said John Facella, director of public safety markets for M/A-COM Wireless Systems, who is a member of a volunteer fire department. Usually, a firefighter keeps the radio in a holster under the turnout coat or inside the chest pocket, leaving only a remote speaker/microphone exposed, he said.
While it might be possible to design a radio that functions when directly exposed to the most extreme heat, this is not a trivial problem, and a solution might be prohibitively expensive, Facella said.
“The thing you need to harden is, in fact, the remote speaker/microphone, which is a fairly simple piece of electronics that is exposed,” Facella said. NIST’s study also included tests on speaker/microphones. The speaker/microphones for all three radios generally performed well under Class I and II conditions. Under Class III conditions, none operated normally.
Mark Krizik, a senior staff engineer for Motorola — who recently joined the NFPA’s electronic safety equipment committee — agreed that most firefighters keep their radios under cover while they work.
“I would not say that heat imposed on the radio is a primary concern for the firefighters,” said Krizik, a fourth-generation firefighter. The building’s construction has a much bigger effect on signal propagation, he said. Also, “smoke and particulates, humidity and moisture, and the position of the radio on the user” each have a much more significant impact on their ability to transceive signals.
Radios that look as though they’ve been destroyed by heat may actually continue to function, Krizik said, citing photos he has seen of equipment ruined when flames suddenly engulfed a room.
“Customers have called us and said, ‘You know, it still works,’” he said. “But you look at the picture of the radio, and it looks like it went through a microwave oven for five hours.”
Because myriad factors affect the performance of electronic equipment at a fire, the NFPA committee’s job is extremely complicated, said Larry Nybert, Motorola’s manager of standards strategy, who has served on the committee since its inception several years ago.
However, he said, “it’s just in its infancy, trying to figure out how to even create a work plan to address so many variables for so many applications, when you start thinking about how many frequency bands there are, and power levels, licensed and unlicensed, voice, video, data.”
NFPA is not the only organization trying to nail down standards for radio performance at a fire scene. A working group within the International Association of Fire Chiefs (IAFC) is exploring how background noises on a fire ground degrade the audio on a digital radio. “Analog radios don’t have the same problem,” said Charles Werner, chief of the Charlottesville (Va.) Fire Department, who chairs the working group.
“Once we identify the full scope and the radios that are affected, as we have solutions that are proposed, new modifications to the radios, we want NIST to be involved to help us validate that it performs to an acceptable level for the fire service,” he said.
Other factors that standards-makers should consider are ambient moisture, high-force rain and wind, and extreme temperature fluctuations. Werner said. Tests also should consider whether equipment could operate safely around explosives and how well it resists exposure to hazardous chemicals, he said.
However, questions of how much abuse a radio can stand may be beside the point, said Steve Rauter, executive director of the Western Will County Communications Center (Wescom), a regional dispatching center in Plainfield, Ill.
“It’s probably interesting to find out survivability ratings for various radios,” said Rauter, a 30-year veteran of the fire service. “But shouldn’t the concern be, ‘Is the firefighter surviving?’”
Indeed, there’s an ongoing debate in the fire service between people who want to encase firefighters and their equipment in as many protective shells as possible, and those who warn that all those layers of protection could create a false sense of confidence, Rauter said.
“Before the days of Nomex hoods and things like that, if your ears started to burn, you knew it was too hot, and you got out,” he said. “Now we’re overprotecting people, and they are staying in longer than they really should stay in. Where that affects radios, I’m not really sure.”
“What NIST is doing is commendable,” Rauter added. “We should know what survivability ratings are for radios. I’m just hoping that people don’t feel that you can walk upright [into] a 1300 degree room and expect to walk back out again.”
|Thermal class||Maximum time (min.)||Maximum temperature (degrees C/degrees F)||Maximum flux (kW/m2)|