Research: Why PASS doesn't always work discovered


Ambient temperature will change the speed and direction of sound, preventing firefighters from hearing some PASS alarms in burning structures

AUSTIN, Texas — Researchers at the University of Texas at Austin are working on building a better Personal Alert Safety System after discovering why some firefighters are unable to hear the device in certain situations.

“There were cases where firefighters would hear the device outside the house,” Joelle Suits, a graduate student at UT-Austin told KUTNews. “But once they got inside, they couldn’t hear it or couldn’t find it and they’re not entirely sure why.”

Researchers will first analyze the sensory environment inside a burning building to get an idea on how firefighters rely on auditory senses.

“They are in pitch black conditions and they have to rely on these other senses — particularly auditory in this case — to try to determine what’s going on,” said D.K. Ezekoye, a mechanical engineering professor at UT and one of the researchers on the PASS project.

They also concluded that hotter temperatures not only cause sound to move faster, but it can actually bend the path of sound. For interior firefighters, this can make it seem like a sound is coming from somewhere completely different than the actual source, according to the report.

The researchers are trying to quantify all the other sounds in a fire and figure out how to design an alarm signal that can compete, according to the report.

“There’s most likely not going to be a specific signal that we come up with where we say ‘OK, this signal right here is the best signal,” Suits says. But there will be some guidelines.

Right now, the NFPA standard for a PASS requires it be 95 decibels. They could find that simply making it louder would help or adjusting the frequency or pitch of the alarm, according to the report.

Separate from this research, the next generation of PASS devices will have a universal sound. Now, each manufacturer uses its own sound and pattern.

Ezekoye explains that in the future there may be some kind of hearing aid or device tuned to pick up and locate a signal from the PASS device, according to the report. The researchers said that audio is still the most reliable alarm method.

“All these other technologies, none of them has worked as well and as reliably as this simple sound beacon at this point,” said Ezekoye. “So we’re not trying to create a revolution, but it’s an evolution in terms of this particular technology.”

The UT researchers hope to have their guidelines for what the alarm should sound like sometime next year.
By FireRescue1 Staff


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