Voice communication system

Last updated: September 2026

What triggers one in Ontario

Article 3.2.4.23 of Division B is the provision that decides whether you are installing loudspeakers or horns. Sentence (1) reads, verbatim from the 2024 Compendium:

Except for Group B, Division 1 and Group F, Division 1 major occupancies, where a fire alarm system is required under Subsection 3.2.4., a one-way voice communication system shall be installed in buildings where a 2-stage fire alarm system is installed and whose occupant load exceeds 1 000.

Read the second half slowly, because the word doing the work is and.

A 3 000-person single-stage building does not trigger this article. Neither does an 800-person two-stage building. Both conditions have to be true at once.

The consequence people miss at design stage

In Ontario the staging decision is fixed by the Code in some occupancies and left to the designer in others. Where it is left open, choosing a two-stage system in a building over an occupant load of 1 000 pulls a voice system in with it, along with amplifiers, speaker circuits, message storage, a microphone position and everything that follows.

That is a substantial cost sitting downstream of a choice that looks free on its own. The staging question is worked through in single-stage versus two-stage, and the mechanics of the alert and alarm signals are in the two-stage system entry.

Voice also changes where the building is operated from. In a two-stage building with voice, the microphone, the controls and the annunciation generally sit together at the CACF, which becomes the position the fire department works from on arrival.

What the messages have to achieve

The performance standard is short. Sentence 3.2.4.23.(2)(b), and the parallel provision at 3.2.4.22.(1)(b), require that messages be audible and intelligible in all parts of the building. That is the whole of it.

Appendix note A-3.2.4.22.(1)(b) explains what intelligible means. A person with average hearing and cognitive abilities has to be able to understand the transmitted messages. The note goes on to say there is no absolute measure that will predetermine the effect of loudspeakers, and that it may be necessary, once the building is furnished and occupied, to add loudspeakers to improve message quality. It refers to ISO 7731 as suggesting a level at least 15 dBA above ambient.

Two things follow that are worth planning around. Intelligibility is assessed in the finished, furnished, occupied building, not from a coverage calculation. And the appendix openly contemplates adding speakers afterwards, which means a project that treats the speaker layout as final at rough-in is carrying a risk it has not priced.

There is no Common Intelligibility Scale number in Ontario's Building Code. If a 0.70 target is being applied on your project it comes from CAN/ULC-S524 or from the specification. See CIS.

How it behaves alongside the audible devices

A voice system does not remove the audibility obligation. Speakers on tone are audible signal devices, and the levels in Article 3.2.4.18 still apply to them: not less than 10 dBA above ambient and not less than 65 dBA within a floor area, and not less than 75 dBA in a sleeping room in a residential occupancy. See fire alarm audibility in Ontario.

There is also a direct interaction with in-suite silencing. City of Markham Builder Tip No. 67, written to the 2024 code, quotes the automatic signal silence conditions in Sentence (12), one of which is that the voice communication system has to have a provision to override the automatic signal silence. A voice system that cannot take back a silenced circuit does not satisfy that condition.

Where the detail lives

Amplifier sizing, speaker circuit classes, tap settings, message content, backup amplifier provisions and how intelligibility is actually measured are all outside the Building Code. They sit in CAN/ULC-S524 and in the project specification, and we do not reproduce paywalled standard text or import the American equivalents.

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