Fire
Alarm Evacuation with Low Frequency Sounder
Is your jurisdiction
enforcing the new code mandated 520 Hz low frequency sounders for
fire alarm audibility yet? If so how are you tackling this new
requirement? And finally did you know that the smoke alarms within the
sleeping rooms and guest units do not need to meet the 520 Hz requirement?
When did this start?
Not a lot of people are
aware that this requirement was originally noted in the (2010) NFPA 72 National
Fire Alarm Code section 18.4.5.3. It states "Effective January 1,
2014, where audible appliances are provided to produce signals for sleeping
areas, they shall produce a low frequency alarm signal that complies with the
following:
(1) The alarm signal shall be square wave or provide equivalent awakening
ability.
(2) The wave shall have a fundamental frequency of 520 Hz +/- 10 percent.
Now we fast forward to 2019.
Note that the (2019)
NFPA 72 Fire Alarm and Signaling Code requirements are the same found in
Section 18.4.5.3
Now let’s break it down.
There are a lot of code sections so stay with me.
The Annex A of NFPA 72
(2019) section A18.4.5.3 lets us know that this section does not cover the
audible requirements of single and multiple station smoke alarms and instructs
us to consult chapter 29 for said requirements.
If you refer to Chapter 29 "Single and Multiple-Station Alarms and
Household Fire Alarm Systems" section 29.3.6 it states the following:
"All audible fire alarm signals installed shall meet the performance
requirements of 18.4.3, 18.4.5.1, 18.4.5.2 and 29.3.8." Please
notice that this section does not include section 18.4.5.3. This may lead one
to believe that single and multiple station smoke alarms for dwelling units do
not need to meet the new 520 Hz low frequency requirements.
The key section to pay attention to here is section 29.3.8 which states
"Notification appliances provided in sleeping rooms and guest rooms for
those with hearing loss shall comply with 29.3.8.1 and 29.3.8.2, as
applicable."
Section 29.3.8.1 "Mild to Severe Hearing Loss. Notification
appliances provided for those with mild to severe hearing loss shall comply
with the following:
(1) An audible notification appliance producing a low frequency alarm signal
shall be installed in the following situations:
(a) Where required by governing laws, codes, or standards for
people with hearing loss.
(b) Where provided voluntarily for those with hearing loss.
(2) The low frequency alarm signal output shall comply with the following:
(a) The waveform shall have a fundamental frequency of
520 Hz +/- 10 percent.
(b) The minimum sound level at the pillow shall be 75 dba, or 15
dba above the average ambient sound level or 5 dba above the maximum sound
level having a duration of at least 60 seconds, whichever is greater."
Section 29.3.8.2 "Moderately Severe to profound Hearing Loss.
Visible notification appliances in accordance with the requirements of
18.5.5.7 and tactile notification appliances in accordance with the
requirements of section 18.10 shall be required for those with moderately
severe to profound hearing loss in the following situations:
(1) Where required by governing laws, codes, or standards for people with
hearing loss.
(2) Where provided voluntarily for those with hearing loss.
What does this mean?
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If we read section
29.3.8 very carefully you will notice the word "AND" between
sleeping rooms and guest rooms for those with hearing loss. This is
telling us that the requirements of section 29.3.8.1 and 29.3.8.2 apply to ALL
sleeping rooms including guest rooms for those hard of hearing.
How does this effect your design ?
To this date there are no UL listed UBC smoke alarms that can produce an
audible tone at 520 Hz. In fact the only manufacture that has a UL
listed 520 Hz low frequency sounder appliance is System Sensor. This
means no more mini horns in the sleeping rooms of R-1, R-2 and R-2.1
occupancies. The only way to accomplish this is by installing a System
Sensor HW-LF (low frequency sounder) or addressable smoke detector with low
frequency sounder base in place of all mini horns. This will give us the
required 520 Hz in all sleeping areas during a general alarm condition.
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How do we accomplish 520 Hz when the Single or multiple station smoke
alarm is activated?
Since there is no such thing as a low frequency LISTED smoke alarm, I propose
installing addressable system smoke detectors in all sleeping rooms and guest
rooms. On top of this an addressable control module will need to be
installed for each residential unit. The control module will then need to
be wired so that it controls an individual NAC (Notification Appliance Circuit)
for that particular unit. Through programming we can activate this
individual control module upon activation of any smoke detectors within the
unit. Lastly the control module for each unit will need to be mapped to
activate during a general alarm condition. This way we are activating the
in room low frequency sounders via the in room smoke detectors as well as any
building wide general alarm device. This method allows us to accomplish
the requirements of section 18.4.5.3 as well as 29.3.8 with listed equipment
and methods.
Are any facilities exempt from this requirement?
Healthcare settings,
correctional/detention facilities, and other facilities where private mode
signaling is employed and where staff are trained to alert and evacuate
occupants according to established protocols are exempt from the low frequency
sounder requirements. In addition, these requirements do not apply to dwelling
unit life safety systems as single- and multiple-station alarms and household
fire alarm systems have requirements outlined in Chapter 29 of NFPA 72. You
should always check with your AHJ for local requirements for your facility.
How does this effect your final cost?
Obviously there is a lot more equipment needed to perform this requirement such
as addressable system smokes and control modules. On top of this the low
frequency sounders are more expensive than mini horns. Also note that the
new low frequency sounders draw more current than mini horns which will
decrease your total allowable appliances per NAC ultimately increasing the
number of required remote power supplies.
This is going to be a huge adjustment for our industry which will ultimately
comes with a large learning curve. I suggest your contact your local AHJ
(Authority Having Jurisdiction) and find out what their interpretations on this
subject are.
Building
operators should consult with their local fire marshals to determine the status
of the regulation's adoption and enforcement in their area to assess their
timeframe for installation. The next conversation should be with dealers to
discuss available options that best fit the building's needs. The ease or
difficulty with which the new requirements are deployed will come down to the
system and the manufacturer. Low frequency devices that can be easily
retrofitted into existing installations are a quick, cost-effective solution
for meeting new code requirements. However, it is also important to understand
that power supplies, audio source units, amplifiers, sounders, sounder bases,
and speakers all play a part in achieving code-compliant 520 Hz signaling.
Special design consideration may be required to accommodate low frequency
notification in current life safety systems.