Notification appliance

A notification appliance is any device that tells occupants the fire alarm system has operated: a horn, a bell, a speaker, or a strobe. Ontario's Building Code does not use that phrase. It regulates the same hardware in two places, as audible signal devices under Article 3.2.4.18 and as visible signal devices under Article 3.2.4.19. Audible appliances have to deliver measured sound pressure levels at the occupant rather than at the device, and visible appliances are required in addition to audible ones, never as a replacement for them.

Last updated: September 2026

What the term covers, and what the Code calls it

Notification appliance is North American trade shorthand for the output end of the system, everything that converts a decision made at the fire alarm control unit into something a person can perceive. In practice that is four families of device: horns, bells, speakers and strobes.

You will not find the phrase in Ontario's Building Code. The Code splits the same hardware into audible signal devices, governed by Article 3.2.4.18, and visible signal devices, governed by Article 3.2.4.19. If you are searching the Compendium, search those two terms, not the trade one.

That split matters because the two articles work differently. The audible article sets levels the sound has to reach at the occupant. The visible article sets conditions under which flashing devices become mandatory. Neither article tells you where to mount anything.

What the audible side has to deliver

The obligation is stated as a level at a location, not as a device rating on a data sheet.

Within a floor area, not less than 10 dBA above ambient and not less than 65 dBA, with intervening doors closed
In a sleeping room in a building of residential occupancy, not less than 75 dBA, doors closed
In a sleeping room in a residential or care occupancy, the device must emit a low frequency signal

A 95 dBA horn on a data sheet proves nothing on its own. The rating is measured at a reference distance in a test chamber, and what the Code cares about is what arrives at the far corner of a furnished room with the door shut. This is why audibility is settled by measurement during verification rather than by counting devices on a drawing.

How they behave on the circuit

Audible and visible appliances hang off notification appliance circuits, which the Canadian standards call signal circuits and most Canadian panels label as NAC outputs. Three practical consequences follow.

They are current-hungry. Every appliance draws in alarm, and the circuit has to hold voltage at the last device on the run. That makes voltage drop and the battery calculation real design constraints rather than paperwork, because the standby and alarm load is dominated by the appliances.

They are supervised. A signal circuit is monitored for faults so that a break shows up as a trouble at the panel rather than as silence during a fire. See supervision.

A fault in one place must not silence another. In residential and care buildings, Ontario Sentence 3.2.4.18.(9) requires in-suite audible devices to be arranged so a fault at one device does not impair the devices serving other suites. That is what drives the choice between Class A wiring and Class B with a suite fault isolator.

Silencing, which people get wrong

City of Markham Builder Tip No. 67, written to the 2024 Ontario code, quotes Sentence (8): an audible signal device located within a dwelling unit shall include a means for it to be manually silenced for a period of not more than 10 min.

Sentence (12) allows automatic signal silence instead, but only on separate circuits and only with conditions: silence cannot occur within the first 60 s of operation or within the zone of initiation, a subsequent alarm elsewhere must reactuate the silenced devices, the devices must be restored to continuous signal after not more than 10 min if the alarm is not acknowledged, and a voice communication system must be able to override the automatic silence. Sentence (13) adds that silenced devices serving dwelling units are reactuated whenever a second stage alarm is transmitted.

What the Code does not give you

Spacing, mounting height, synchronization, candela selection and the class definitions themselves all live in CAN/ULC-S524, which is copyrighted and sold. We do not reproduce it, and we do not substitute NFPA 72, which is a different standard in a different code system.

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