NIST tests firefighter tracking devices for radio-frequency interference
Updated NFPA standards soon will be available for public comment based on NIST studies of wireless radio-frequency interference issues between personal alert safety systems and other wireless devices. NIST scientists currently are completing their testing of wireless PASS alarms against interference caused by radio-frequency identification (RFID) systems that can be found in manufacturing warehouses and other buildings, said Kate Remley, the NIST research scientist spearheading the project.
“RFID is representative of a typical RF-interference source that a firefighter might encounter on the fireground,” Remley said. “So the study investigates how resilient RF PASS is against other unintentional RF sources.”
PASS devices were designed to activate an audible alarm if a firefighter becomes incapacitated — leading to device-performance standards found in NFPA 1982. However, devices were required only to detect motion and didn't have to transmit the data wirelessly. Now, PASS systems have a wireless link connecting incident command base stations and portable units that can transmit a “firefighter down” alarm.
However, as RFID becomes popular for location tracking, or may be present in warehouses or other buildings where a fire occurs, there is potential for significant wireless interference with PASS device alarms, Remley said. The study will test those systems in order to identify a generic class of interferers at an incident that could disrupt the alarm’s wireless communication.
Preliminary results show that, when signals are weak due to environmental or other conditions, a portable PASS unit’s receipt of an alarm from its base station becomes more likely to fail in the presence of only moderate RFID interference, Remley said. Strong interference caused longer and variable delays that sometimes exceeded a minute, which is defined by the researchers as a signal failure.
Remley said the NFPA asked the institute to determine PASS devices’ reliability in fire environments, develop manufacturing standards and later release operational best-practices guidelines. Both studies will support the development of technical standards to govern the performance — such as signal penetration into buildings or acceptable transmission quality — for new and existing RF-based PASS emergency equipment.
"There are few standards available that tell firefighters when and where they can safely deploy these devices," Remley said. "As with every wireless system, the technology won't work in every situation so we are … developing methods so firefighters will know when they can expect PASS devices to work and in what situations."
The NFPA technical committee on electronic safety equipment will consider adopting the NIST recommendations as part of revised PASS performance standards after a public comment period expected to open in mid-September and run through March 2012, Remley said.