Developed by the National Fire Protection Association (NFPA), the current standard that governs these devices, NFPA 1982, addresses requirements for devices that provide an audible signal only. Since the standard was last updated, a new generation of devices has incorporated wireless transmitters to send a signal to incident commanders who may be out of earshot of the audible alarm.
The National Institute of Standards and Technology (NIST) is developing a standard method of testing PASS devices. The NFPA could decide to include NIST’s tests in the next version of NFPA 1982, which could be released in 2013.
According to Kate Remley, who leads NIST’s Wireless Systems Metrology project, there are three factors that can impede a signal from a wireless PASS being transmitted reliably: signal attenuation; fragmentation due to reflection that garbles the received signal; and interference from other radio frequency devices, such as radio frequency identification tags (RFID), in the vicinity.
In testing the portable PASS device, an RFID tag and reader were placed in a test chamber, while the PASS base station was in a separate room. Researchers evaluated performance at various levels of signal strength and interference. “We were able to see at what level the transmission failed when it was subjected to a certain amount of interference,” said Remley. “Now we have a way to test this in a laboratory environment that is very controlled.”
Two variables considered in the test included different kinds of interference, such as radio frequencies from RFID transmitters used for tracking goods in warehouses and FCC requirements for such interference.
“This is sort of a first step where we have developed the test method,” Remley said. “Now we just need to extend that a little bit to cover other types of interferers just to get the data, then we do verification tests out in the field.”
This group of tests involved personal alert safety systems that transmitted wireless signals directly from the device to a receiver. Remley said a future test would involve PASS devices that could create a wireless mesh network to relay a signal from a firefighter in trouble to the status screen at the incident command post.
The methods developed in the study can test interference in other wireless devices such as radios, hands-free cell phone headsets, local area networks and urban search and rescue robots, according to NIST. This could be of further use to the first responder community as it seeks technology that includes multiple sensors in remote vital sign monitoring devices.
