Audible Fire Alarm Coverage

[WileMech]

Hello. I am developing a fire alarm system for a parking garage. NFPA 72 Code reports that an audible fire alarm should be a minimum of 15 db above the prevailing sound level of a room. My question is concerning how much area such an alarm would cover. Right now I am assuming am audible coverage area of 30 ft. per alarm. Is this a correct assumption? Any help on this matter would be greatly appreciated.

-WileMech

 

[davidbeach]

What does the project electrical engineer have to say about this? Or, is he too busy doing the ventilation design?

 

[rbulsara]

Ask fire alarm vendors or device manufactureres for some guidance. Typically audible devices located between 40 and 60 feet can do the job. Audible coverage varies with ouput db levels (loudness) of the devices.

 

[JLSeagull]

In industrial plants, the audible alarm people suggest to place the alarm near the highest noise sources. I have seen football field sized multiple deck offshore platforms with devices located near the corners and midfield. These could be nearly 50 meters between devices using loud PA speakers with tone generators.

 

[tommom]

Look at the SFPE handbook - there is a calculation procedure in there that should give you just what you need for audible alarm coverage. The calculation is fairly straightforward - adding & subtracting dB based on the construction.