Is the smoke alarm required to be low frequency in sleeping area?

Merry Christmas

zemingduan

Member
Location
Philadelphia,PA
Occupation
Electrical Designer
Per NFPA 2016 18.4.5.3, the audible appliances in sleeping areas shall be the low frequency type. We are now required a low frequency sounder or sounder strobe in sleeping/dwelling units to notify the fire alarm signal of the building fire alarm system. Are the smoke alarm in side and outside the bedrooms in a dwelling units, or sleeping area in hotel etc. required to be low frequency type? I am not talking about the smoke alarm instead of smoke detector that is connect to the fire alarm system.

However I can't find a manufacture that has low frequency smoke or smoke/co alarm. Do you guys know any manufacture that has low frequency smoke or smoke/co alarm.

Another option is to install smoke detector with low frequency sounder base in sleeping/dwelling units and connected to building fire alarm system. But configure those smoke detectors to activate only the sounder base in the unit rather than the building fire alarm system. But this will cost much more than smoke alarms. One smoke alarm is only $30-$50 bucks I guess. You will also need extra cost for programing and wiring. Besides, when I look into the products from silent knight, I think the smoke detector with sounder base only work in addressable fire alarm system. In this option, you will need addressable fire alarm system for 3-4 units multifamily.
 

zemingduan

Member
Location
Philadelphia,PA
Occupation
Electrical Designer
I do more research and find below very useful information in an article posted on NFPA official website (https://www.nfpa.org/News-and-Resea...021/01/22/Low-Frequency-Fire-and-Smoke-Alarms):

"Low frequency 520 Hz alarms were required for single and multiple station alarms, smoke alarms not connected to a building fire alarm, where the occupants have mild to severe hearing loss." - NFPA 72 29.3.8.1 since 2010 edition.

"The 2013 edition of NFPA 72 broadened the use of low frequency alarms by requiring all audible appliances initiated by the building fire alarm that are provided in sleeping areas to wake sleeping occupants to be a low frequency 520-Hz alarm. " -NFPA 18.4.5.3. First appears in 2010 edition. It states this requirement effective from 1/1/2014.

Conclusion:

"As you can see, NFPA 72 only mandates the use of low frequency 520 Hz alarms for audible alarms, initiated by the building fire alarm system, in areas where the alarm is intended to wake sleeping occupants and only for audible alarms initiated by smoke alarms, not initiated by the building fire alarm system, in sleeping areas where occupants have mild to severe hearing loss. "

My understanding, the single & multiple station smoke or smoke & co alarms are not notification appliances. Thus they are covered by Chapter 29 instead of Chapter 18.

NFPA 101(if you area adopt NFPA 101, Philadelphia doesn't adopt NFPA 101) has stricter requirements since 2021:

"Changes to the 2021 edition of NFPA 101, Life Safety Code strive to make use of low frequency alarms more consistently throughout all sleeping areas. The changes require that, where the occupancy chapter mandates their use, audible alarms in sleeping rooms initiated by the building fire alarm system and audible alarms in sleeping rooms initiated by the activation of a smoke alarm, not the building fire alarm system, must result in a low frequency 520 Hz alarm. Two of the residential occupancy chapters in NFPA 101, new hotels and dormitories and new apartment buildings now require the use of low frequency alarms for audible notifications activated by both smoke alarms and the building fire alarm system."
 

zemingduan

Member
Location
Philadelphia,PA
Occupation
Electrical Designer
I also find below from another article (https://www.affiliatedinc.com/do-single-station-smoke-alarms-have-low-frequency-sounders/) stating the reason that why regular smoke alarm is not low frequency type:

" I’ve only found one manufacturer that has a 520 hz smoke alarm & it costs around $200. This seems like a no brainer for smoke alarm manufacturers, so why aren’t there any cost effective 520 hz smoke alarms available? The short answer is that in order to produce a 520 hz tone loud enough to meet audibility requirements (75 dB at the pillow), the speaker has to be larger than what can fit in a standard smoke alarm. "


Hope this information will also help you guys!
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
The problem with developing low frequency smoke alarms or smoke/CO alarms is that creating the 520 Hz signal requires a high fidelity speaker, and it draws a significant amount of energy. You probably couldn't create a sealed 10-year life device that operates on battery only, and the transformer for the sounder is fairly bulky, so the size of the unit starts to become significant. Simplex and Siemens, for two, have sounder bases capable of generating the 520 Hz tone. No one currently has a 520 Hz smoke alarm. It is also not required in residential occupancies other than commercial (dorms, hotel rooms, etc) unless you are under the 2021 edition of NFPA 101.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Interesting.
I don't hear the low battery alerts from our home detectors very well. Some phone tones not at all. Even when while holding it and knowing it is sounding. Best alert from my phone is to have it on vibrate and set it on the small glass topped table that sits on a hardwood floor in our living room.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Interesting.
I don't hear the low battery alerts from our home detectors very well. Some phone tones not at all. Even when while holding it and knowing it is sounding. Best alert from my phone is to have it on vibrate and set it on the small glass topped table that sits on a hardwood floor in our living room.
The low battery chirp can be elusive, and because it is the same sounder (3150 Hz) as the alarm, it's highly non-directional. My detectors have a voice component that says "Warning, low battery" after the chirp. Makes it much easier to figure out which alarm is in trouble.
 
Top