NFPA 72 - Mixing Speakers and Horns for Fire Alarm
Are we Allowed to Mix Voice Evacuation Speakers with Horns for
Fire Alarm Occupant Notification?
This is a question that comes up from time to time and a lot of
people have mixed feelings. In a nutshell, the question in a more
specific format is as follows: "Am I allowed to install voice evacuation
speakers and standard temporal code-3 horns within the same fire alarm system?”
To make things fair, we will consult the Standards of NFPA 72 as well as
the Code of the International Fire Code Section 907.
What code and standard sections relate to mixing audible signals
for fire alarm evacuation?
Here are a list of codes
and standards that dance around the topic:
NFPA 72 2019 Sections
NFPA 72 2019 Sections
·
10.10.7
·
18.4.1.1
·
18.4.2.1
International Fire Code
2015
·
Section 907 "Fire
Alarm and Detection Systems"
NFPA 72 2019 Standard Dissection
NFPA 72 2019 - Section 10.10.7 states "Alarm
evacuation signals shall be distinctive in sound from other signals and shall
comply with section 18.4.2 and their sound shall NOT be used for any other
purpose."
NFPA 72 2019 Section 18.4.2.1 States "Distinctive
Evacuation Signal" "To meet the requirements of section 10.10, the
alarm audible signal pattern used to notify building occupants of the need to
evacuate (leave the building) or relocate (from one area to another) shall be
the standard alarm evacuation signal consisting of a three-pulse temporal
pattern. The pattern shall be in accordance with figure 18.4.2.1 and
shall consist of the following in this order.
1.
ON phase lasting 0.5
seconds +/- 10%
2.
OFF phase lasting 0.5
seconds +/- 10% for 3 successive "on" periods
3.
OFF phase lasting 1.5 seconds +/-
10%
This section in short
describes the three-pulse temporal pattern of an audible EVAC signal. This
temporal code-3 signal is generated by horns as well as speakers.
Remember with voice evacuation speakers, there is still a requirement to
have the temporal code 3 whoops between the voice message.
What Does a Distinctive Signal Really Mean?
When the term
"distinctive evacuation signal" is used, it's not meant to cover
voice evacuation speakers versus horns or bells but to ensure that a temporal
3-pulse pattern or other approved audible tone is used for fire alarm
evacuation and ONLY that.
Example: A 4-wire CO detector tied to the building FA system. If the CO
detector activates, its internal sounder will alert nearby occupants of dangerous
levels of CO via a temporal code-4 audible output. These are typically
tied to the FA system via a monitor module and activate a non-latching
supervisory signal at the FACU. However for the sake of this post, lets say the
CO detector activates speakers in the affected area. These speakers would need
to produce the same temporal code-4 sound as it is not a fire alarm signal
rather a CO alert tone.
A distinctive evacuation signal in the minds of NFPA 72 is simply put, a
temporal code 3 or other approved audible tone. Bottom line is the
distinctive signal can ONLY be used for fire alarm evacuation and nothing
else.
What about NFPA 72 2019 Section 18.4.1.1?
Another standard section
that trips people up on this topic is NFPA 72 2019 - Section 18.4.1.1.
The standard states "An average ambient sound level greater than
105 dBA shall require the use of a visible notification appliance(s) in
accordance with Section 18.5 where the application is public mode or Section
18.6 where the application is private mode."
Section 18.4.1.1 is not
so much for horns and speakers but strobes in areas that have an average
ambient sound level of 105 dB or greater. The reasons for this is 15 db over
average or 105 + 15 = 120 dB (public mode) or 10 dB over average or 105 + 10 =
115 dB (private mode). This violates the Section 18.4.1.2 which sets a limit
not exceed 110 dB for the FA audible appliances.
The language that hits home with this topic is
actually found in the Annex. A.18.4.1.1 states "The
code does NOT require that all audible notification appliances within a
building be of the same type. However a mixture of different types of
audible notification appliances within a space in not the desired method.
Audible notification appliances that convey similar audible signals are
preferred. For example, a space that uses mechanical horns and bells
might not be desirable. A space that is provided with mechanical horns
and electronic horns with similar audible signal output is preferred."
When is Voice Evacuation Required in Place of Horns?
In order to find out
WHEN something is required in the world of Fire Alarm, we have to consult a
CODE. Section 907 of the International Fire Code covers "Fire
Alarm and Detection Systems". This is the section where all the
fire alarm requirements per occupancy group are broken down.
Some examples of voice evacuation requirements are as follows:
Some examples of voice evacuation requirements are as follows:
·
IFC Section
907.2.1.1 Group A occupancies with 1000 or more requires voice
evacuation
·
IFC Section 907.2.3
Exception #2 Group E occupancies with more than 100 persons requires
voice evacuation
·
IFC Section 907.2.13
High-Rise Buildings require voice evacuation.
·
IBC Chapter 3008 Occupant
Evacuation Elevators require voice evacuation
The following is a good example of two separate types of fire alarm occupant
notification methods being used for one facility. Prior to the newer
versions of the International Fire Code, it was typical to have Group E
occupancies (schools) with horns in corridors, restrooms, classrooms, etc.
However if the auditorium or gym (Group A) has an occupant load of 1000
or more, voice is required. In these cases you would have a standalone voice
panel triggered to activate the speakers in the gym/auditorium on general
alarm. Currently the 2015 IFC is requiring voice throughout E occupancies if
the occupant load is greater than 100 so this is no longer an issue.
To circle back to the original question, "Am I allowed to install voice
evacuation speakers and standard temporal code-3 horns within the same fire
alarm system?" YES, by code, you are allowed to install different methods
of audible tones used for evacuating occupants as long as they have ONE
"distinct evacuation signal". Referencing NFPA 72 2019
A.18.4.1.1, it is not desirable to have different types of audible appliances
producing conflicting tones. This is based on the different audible
appliances being installed in one area where they could both be heard at the
same time. For example it would not be desirable to have horns in
classrooms and voice evacuation speakers in the common corridor where larger
groups of occupants come together. During an evacuation, the classroom
doors would be opened to the corridor and the temporal 3 output from the horns
would drown out the speakers thus eliminating any sort of intelligibility.
Even if you provided the correct digital audio file to mirror the horn's
temporal sound output through the speakers, the voice portion of the evacuation
message would still be played during standard code 3 cycles on the classroom
horns.
Additional VOICE requirements for speakers can be seen in NFPA 72 2019 Section "18.4.1.5".
Ref: NFPA Free login
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Interesting topic as dorms nowadays have both Sounders to wake people up and a voice evac system. One of the dorm buildings here where I am had 520Hz horns installed in every bedroom because people would sleep through the voice evac messages that only played in the hallways.
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what we need to do if both speaker and horn/flasher installed in the same corridor and lobby in high rise tower ?
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