NFPA 72 now requires a 520 hz square wave fire alarm signal in smoke detector sounder bases provided for publicly available sleeping areas. The 520 hz tone has been shown as more effective in waking people of a certain age (ahem), deep sleepers or those that may have had a few too many the night before. Most commercial fire alarm manufacturers have a smoke detector sounder base that provides this tone at an acceptable dB output. However, a lot of hotels and SROs use single station smoke alarms. To clarify, single station smoke alarms are the type you may get at your home improvement store, whereas smoke detectors are connected to fire alarm systems. If a municipality is enforcing the 2013 version of NFPA 72 or later, designers of record are going to have a real problem achieving code compliance if they are trying to utilize smoke alarms in sleeping units. In fact, 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. System smoke detectors with sounders have separate bases and have the space to fit these sounders. They don’t have to fit the detection components in a single unit like the smoke alarms. If you have to supply sleeping area detectors for a hotel in a municipality that enforces the 2013 version of NFPA 72, and it has a fire alarm system, count on using the system to provide detection and proper audibility in the sleeping areas. There are no cost effective single station smoke alarms that can be utilized at this time.
Gamewell-FCI has 520 hz detctors that can be programmed to function like a single station smoke alarm. Contact Affiliated Fire Systems for more information on how to deploy them in your building’s design.
Gene Rowe – Affiliated Fire Systems
About Gene Rowe
The reference to 18.4.5.3 in section 29.3.6 was a mistake. The low frequency requirement was never meant to encompass single/multi-station alarms with the exception of specified hearing-impaired sleeping spaces. The two links below are the proposal to revise the 2010 NFPA 72 edition to clarify this confusion (and remove 18.4.5.3 reference) and the original approval. This revision was adopted in later editions.
Link to PDF: https://www.nfpa.org/Assets/files/AboutTheCodes/72/ProposedTIA1048NFPA72.pdf
https://www.nfpa.org/assets/files/aboutthecodes/72/tia72-10-5.pdf
Gene…any updates from manufacturers for a 520Hz single station sounder? Not sure when your article was printed but I STILL cannot find one that meets NFPA 2013.
Hi Chris,
Still no single station smoke alarms with a built in 520 hZ low frequency sounder. The same reasons are why. The single station manufacturers can’t manufacture a speaker small enough to be placed directly on the circuit board of the single unit smoke alarm. Additionally, in talking with my Honeywell engineering contacts, the various manufacturers feel there just isn’t a large enough market to justify the costs involved with developing this product. They prefer to mount and control a sounder where needed. Single station alarm manufacturers will tout a spectrum of lower frequencies designed to be heard by those with age related hearing loss, but they’re not the 520 hZ square wave signal called for in NFPA 72. I’ll post anything new on the subject if I catch wind of it.
Gene Rowe
Gamewell-FCI by Honeywell
Affiliated Fire Systems
Downers Grove, IL
I think it is a misconception of code interpretation. “NFPA 72 now requires a 520 hz square wave fire alarm signal in smoke detector sounder bases provided for publicly available sleeping areas.” is located in section 18 under notification appliances, which requires horns (horn strobes) to be activated on general alarm in sleeping areas.
Section 29 “Single and Multiple Station Alarms AND Household Fire Alarm Systems” requires 520 Hz tones only in section 29.3.8.1 in Mild to Severe Hearing loss areas.
It’s based on NFPA 72 2013 edition but as far as I know 2016 doesn’t change much this concept.
Hi Jack,
It’s certainly a valid comment as this can be a confusing requirement, but NFPA 72 Chapter 18.4.6.3 does state “Audible appliances provided for the sleeping areas to awaken occupants shall produce a low frequency alarm signal that complies with the following: 1. The waveform shall have a fundamental frequency of 520Hz +/- 10%. 2. The notification equipment shall be listed for producing the low frequency waveform.” This requirement, and the article, is applied to sleeping areas that would notify occupants via fire alarm system connected devices & is not intended to replace or supersede the hearing loss notification method stated in Chapter 29 nor a single/multiple station device not connected to a fire alarm system. However, if the occupancy uses a fire alarm system to achieve the audibility requirements of a sleeping area, it must use a low frequency signal in the sleeping area. An example would be in a new or renovated hotel that can use single station smoke alarms in the units. If that room smoke alarm goes off, the audible signal does not have to be low frequency since you’re not using the fire alarm system to achieve 75 dB at the pillow. The internal sounder in the smoke alarm does that. However, if a corridor smoke detector goes off or a pull station is activated, the general evacuation horns in the corridor are not going to raise the sound level at the pillow to 75 dB. You need a fire alarm system supervised sounder in the room for that & that sounder has to be low frequency. Now you have an unmonitored, high voltage smoke alarm that can be tampered with and a low voltage, red sounder mounted on the wall. Twice the pipe, twice the wire, twice the footprint and you’d still have to make a connection to (& provide power from) the fire alarm system. Since you need a smoke detection device & 75 dB at the pillow on general alarm in this room, why not put a single footprint, low voltage, low frequency device that can be programmed to perform as a single station device and be programmed to turn on its sounder base when a general alarm condition is present? 2 pairs of low voltage wires to a single point using a single pipe costs a lot less than the labor to install & separately power 2 devices per room. Plus the hotel would know if it’s dirty, removed or if it activates. I do appreciate the comment Jack & hope I’ve replied to it adequately. I get a lot of calls from design engineers that struggle with the application of the low frequency requirement.
Gene Rowe
Gamewell-FCI by Honeywell
Affiliated Fire Systems
Downers Grove, IL
There are some products on the market such as Loundenlow, SafeAwake, and Lifetone, but they sell for
$180-$250, This is too costly for most seniors. Kidde tried to bring a low frequency alarm on the market
back in 2005, but they pulled it, it cost $90 and had to be used only with their wireless smoke alarm.
I have designed a $40 product (retail price) with my local electrical engineering firm. Need to build the prototype for proof off concept and component costing. Trying to get companies interested in working with me on this low cost solution, but so far no interest.