An investigation into factors that influence the effectiveness of Visual Alarm Devices

Building on previous BRE research this study aimed to investigate five factors that influence the effectiveness (in terms of subjective responses) to red and white VADs (either Xenon or LED). Over 3 phases and using a number of VADs supplied by the stakeholder group, this work investigated how VAD performance is influenced by: 

• the wall surfaces present in a room,
• direct or indirect viewing of the VAD by people present in the space,
• varying pulse durations of LED VADs (5 - 200ms) and comparing with Xenon, 
• the VAD colours (red and white),
• four different ambient light level conditions ranging from 80-800 lux.

The stakeholder group, comprising the Fire Industry Association, twelve VAD manufacturers and one independent consultant, steered the work and reviewed the data that was gathered.
The work supported the previous finding that as the pulse widths of LED devices shorten the attention drawing effectiveness increases. It also showed that red and cool white LED VADs resulted in similar subject responses. In all four ambient light level conditions the Xenon VAD was more effective at drawing attention than the LED VADs of different pulse durations.
It was observed that subject responses under low ambient light level conditions were always better than high. Subject responses to white and red VADs demonstrated inconsistent variability and further work, with a greater selection of VADs, is recommended to investigate this further.