How effective are Xenon and LED VADs? The effectiveness of Xenon and LED visual alarm devices (VADs), used to warn deaf and hard of hearing people of fire, has been investigated in a recently completed research project.
The purpose of this research project was to compare the responses of a group of participants to flashing Xenon and LED devices of varying pulse durations. One Xenon device, three cool white LED devices (of 40, 20 and 10 millisecond (ms) pulse durations) and two warm white LED devices (of 40 and 20ms pulse durations) were used.
The flashing signals were presented individually to 96 participants who were seated in front of a screen and occupied in a written task. The tests were performed in high and low ambient light level conditions. The devices were flashed one at a time, and from a distance of 19m were gradually brought closer to the screen until the subjects responded. The response data was processed to identify the effective illumination levels required to alert people to the flashing signals from the six devices.
Analysis of this data revealed that as the pulse durations of LED devices shorten the attention drawing effectiveness increases. It also demonstrated no significant difference in responses between warm white LED devices and cool white LED devices. The Xenon and 10ms cool white LED device had similar responses; however, a cool white LED device with a pulse duration of 5ms may out-perform a Xenon device.
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