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The deaf alerter is a good product, but it is never mentioned that most deaf people CAN hear fire alarms because of the frequency used in sounders. Many now also incorporate visual alarm devices (VAD) as back up or where there is a primary need for visual warning.
The door guard demo equally did not mention that such products should NOT be fitted to fire doors in a number of key locations, as areas without any smoke detection would allow the smoke to spread BEFORE any alarm is sounded. See BS 7273-4, which has just been updated.
The definition of deaf is not being able to hear below 85 dBA, the decible level of a fire alarm at the bed head is 75 dBA. I’d be suprised if “most deaf people can hear fire alarms” as they are fairly high frequency, peaking at between 1000 Hz and 2.7kHz. Low frequencies are the most successful for waking people unfortunately in the UK they aren’t installed. BS7273-4 is all about the system, most fire alarm panels aren’t actually capable of providing a “critical” category of actuation. Dorgard is classified as part of a normal system. The standard is careful… Read more »