Where Ontario's Fire Alarm Rules Differ from the National Building Code

The short version

One provision we checked matches word for word: one-way voice communication, 3.2.4.23.(1). That is in here too, because a comparison that only reports differences is not a comparison.

How the Ontario Building Code works now

If you learned this trade before 2025, the thing to unlearn is that Ontario has its own Building Code book.

O. Reg. 332/12, the old full-length Ontario Building Code, was revoked effective 1 January 2025 by O. Reg. 163/24, s. 3.

What replaced it is O. Reg. 163/24, and it is one page long. Section 1, verbatim:

The code issued by the Canadian Commission on Building and Fire Codes, part of National Research Council Canada, known as CCBFC NRCC-CONST-56435E, "National Building Code of Canada 2020", (First Printing), as amended by the document entitled "Ontario Amendments to the National Building Code of Canada 2020", dated July 17, 2026 and issued by the Ministry of Municipal Affairs and Housing, are together adopted as the building code.

So the Building Code in Ontario is now two documents read together:

1. NBC 2020, First Printing — the national code, unchanged, published by NRC.
2. The Ontario Amendment Document — dated 17 July 2026, issued by MMAH.

That July 2026 date is recent. O. Reg. 242/26, verbatim, is the whole amendment that put it there:

Section 1 of Ontario Regulation 163/24 is amended by striking out "April 21, 2026" and substituting "July 17, 2026".

MMAH does not publish the amendment document. From ontario.ca, verbatim:

The structure of the Ontario Building Code regulation has changed. The new Building Code regulation is one page long and adopts the National Building Code of Canada 2020, except where it is amended by the Ontario Amendment Document (that is, the "Ontario Amendments to the National Building Code of Canada 2020"). The full-length version of the Building Code will no longer be available on E-laws. Email us to request a copy of the Ontario Amendment Document.

The request address is Ontario.Amendment.Document@ontario.ca. Note that the ontario.ca page carrying that text now displays a banner saying it is no longer up to date.

That is the whole problem this article exists to address. The document that states every Ontario-specific rule cannot be opened in a browser, and the free consolidated text that can be opened is eighteen months behind it.

The transition rule, and the condition Ontario's own summary leaves out

If your project is on an old permit, O. Reg. 163/24 s. 2 is what keeps the revoked code alive for you. Verbatim:

(1) Subject to subsection (2), Ontario Regulation 332/12 (Building Code) made under the Act, as it read on December 31, 2024, is deemed to continue in force with respect to construction, (a) for which a permit has been issued on or before December 31, 2024; or (b) for which the working drawings, plans and specifications are substantially completed on or before December 31, 2024, and for which an application for a permit is made on or before March 31, 2025 under that regulation, as it read on December 31, 2024.

(2) Subsection (1) does not apply unless the construction is commenced within six months after the permit is issued.

Read subsection (2) twice. Ontario's own plain-language timeline page describes the grandfathering without mentioning the six-month condition. It is in the regulation. A project sitting on a pre-2025 permit that did not break ground within six months of issue does not get the old code — it falls to the 2024 Code, with the renumbering and the differences below.

That is worth checking on any stalled job before you scope a fire alarm design or a verification against the wrong document.

Getting both documents, free

NRC's own page states that the codes are "available directly through the NRC Publications Archive in free electronic format." Take the First Printing, not a later printing — that is the one named in the regulation.

The Compendium is the useful one for daily work because, in MMAH's words, it "consolidates the National Building Code and the Ontario Amendments into one single, comprehensive document." It is also the one that is out of date: it is the January 16, 2025 consolidation, and four amendment-document versions have been adopted since — O. Reg. 247/25, 110/26, 119/26 and 242/26.

Everything below was found by comparing that January 2025 Compendium against the NBC 2020 PDF. Both are free. You can reproduce all of it yourself in an afternoon.

Difference 1 — every article number in the fire alarm range moved by two

This one bites first, because it makes old paperwork look wrong when it is only old.

Installation and verification stayed at 3.2.4.5. Everything from manual stations onward shifted by two, and the manual stations article lost the word "Pull" from its title.

A 2023 report citing 3.2.4.20 for audibility is not wrong, it is dated. But a 2026 report citing 3.2.4.20 for audibility is pointing at the smoke alarm article, which is a different thing entirely. More on citing the right instrument in which ULC edition applies.

Difference 2 — installation and verification, 3.2.4.5

Ontario reworded this article. Both versions reference the 2019 editions of CAN/ULC-S524 and CAN/ULC-S537.

We are not going to claim this changes anything. It reads like a drafting preference, not a technical variation.

The interesting part is that Ontario bothered. These three edits prove the amendment document reaches into Article 3.2.4.5. Anyone assuming "installation and verification is just NBC in Ontario" is assuming something the text disproves — and if the amendment document touches an article to fix a comma, it can touch the same article to change a requirement, in a version you cannot read. What S537 verification actually covers is in what S537 verification involves.

Difference 3 — types of systems, 3.2.4.3: Ontario adds schools

Ontario carries a clause (1)(d):

a single-stage system in elementary and secondary schools, except for a special needs facility

NBC has no such clause. NBC's list runs (a) to (d) and ends with "a single- or 2-stage system in all other cases."

So in Ontario, elementary and secondary schools are named in the Code as single-stage, with a special needs facility carved out. Design a school from the national code alone and you would land in NBC's catch-all, which permits either. Background on the two arrangements is in single-stage vs two-stage fire alarm systems.

Difference 4 — two-stage escalation, 3.2.4.4.(2)(b): a hospital carve-out

Ontario, verbatim:

except for a Group B, Division 2 occupancy, automatically cause an alarm signal to sound if the alert signal is not acknowledged within 5 min of its initiation

NBC has no Group B, Division 2 exception. In the national text, the escalation applies without that carve-out.

Two things to take from this.

Group B, Division 2 is treatment and care. Ontario exempts those buildings from the automatic escalation to a general alarm signal.

And in both codes the escalation is acknowledgement-conditional, not a timer. The signal escalates if the alert is not acknowledged within 5 min. An acknowledged alert does not escalate at 5 min. That distinction gets flattened in training material and it is worth being precise about.

Difference 5 — two-stage systems in hotels, 3.2.4.4.(2)(d): Ontario-only

Ontario, verbatim:

in a building containing a hotel, (i) cause an alarm signal to sound in the initiating fire zone in the hotel, and (ii) cause an alert signal to sound throughout the hotel and such parts of the building as is necessary to alert hotel staff.

NBC has no clause (d) at all. You can see the seam in the drafting: NBC's clause (c) ends with "and", because in NBC it is the last clause. Ontario's clause (c) does not, because Ontario has one more.

This is a substantive, Ontario-only sequence of operation: alarm in the initiating zone, alert everywhere else in the hotel plus whatever is needed to reach staff. If you are programming a matrix for a hotel in Ontario off the national code, this clause is not in your source document.

Difference 6 — sleeping room audibility, 3.2.4.18.(5): Ontario is narrower

This is the one that runs the opposite way from what people expect. Ontario usually adds. Here it subtracts.

Ontario dropped care occupancies from the 75 dBA floor.

And Ontario's own article does not agree with itself about scope. Sentence (6), the low frequency requirement one sentence later, still reads "residential or care occupancy." Same article, same subject, two different scopes.

We are reporting the mismatch. We are not going to speculate about whether it was intended. If you have a care occupancy sleeping room in front of you, take it to the AHJ before you design to either reading. The full audibility picture is in fire alarm audibility in Ontario.

Difference 7 — the maximum sound pressure level, 3.2.4.18.(4)

Three documents, three different maximums, and Ontario's printed text does not hold together.

Ontario Compendium, verbatim:

(4) In all normally occupied spaces, the fire alarm signal sound pressure level (a) shall be not more than 110 dBA when measured at a distance of 3 m from the device, or (b) is permitted to be more than 100 dBA provided the sound pressure level measured 2 000 mm above floor level is not more than 100 dBA.

Clause (a) sets 110. Clause (b) grants relief against a 100 that clause (a) no longer states. The relief has nothing to attach to.

Revoked O. Reg. 332/12, Article 3.2.4.20.(4)(a): read 100 dBA at 3 m. With 100 in clause (a), the pair reads coherently — a 100 dBA ceiling at 3 m, with an alternative letting you exceed it provided you hold 100 dBA at head height. Ontario appears to have amended clause (a) alone.

NBC 2020 has neither clause:

The fire alarm signal sound pressure level shall be not more than 110 dBA in any normally occupied area.

No 3 m basis. No 2 000 mm alternative. No clause structure at all.

We are not going to pick one. We do not know which is operative, and a summary site that guesses at a maximum sound pressure level is worse than no summary site.

This is also the single most likely item in this article to have already been fixed. A clause pair that contradicts itself is exactly what a housekeeping amendment cleans up, and four amendment-document versions have gone by since the text above was printed.

What to do: if a maximum matters on your job, request the 17 July 2026 amendment document from Ontario.Amendment.Document@ontario.ca, read Article 3.2.4.18 in it, and confirm with your AHJ. One email settles it.

Difference 8 — visible signals, 3.2.4.19: three Ontario differences

The strobe article has more Ontario content than any other in the range.

Three of these expand coverage.

Group A gets added to the public corridor clause (e). NBC starts that list at B.

Clause (f) reaches beyond corridors. Ontario catches floor areas, or parts of floor areas, where the public may congregate in a Group A occupancy. NBC's version is corridors only.

Clause (i) has no national equivalent whatsoever. Strobes in living spaces in residential suites in Group C apartment buildings is an Ontario rule and only an Ontario rule. Design an Ontario apartment building from the NBC PDF and you will miss it — and it is the kind of miss that shows up at verification, not at plan review.

Ontario also opens the article with an exception referring to Sentence (4) that the national text does not carry.

Difference 9 — smoke alarms, 3.2.4.20.(20): retirement homes

Ontario, verbatim:

Smoke alarms required in suites in a retirement home or smoke detectors permitted to be installed in lieu of smoke alarms as provided in Sentence (10) shall upon actuation provide an audible and visual signal to staff serving those suites, so that the suite containing the actuated smoke alarm or smoke detector can be easily identified.

The string "retirement home" does not appear in NBC's article.

This is a real functional requirement: staff annunciation, audible and visual, with per-suite identification. It is not a note or an appendix suggestion. And it is invisible if your source document is the national code.

Difference 10 — emergency power, 3.2.7.8.(3): a retirement home tier

Ontario inserts a clause (b)(ii.1):

1 h for a building that contains a Group C major occupancy retirement home and that is not within the scope of Subsection 3.2.6.

NBC runs (i) through (v) with no retirement-home entry. The numbering gives it away — "(ii.1)" is what you get when you slot a new tier into an existing list rather than renumbering it.

Everything else in the sentence matches between the two:

If you are running a battery calculation for a retirement home in Ontario, that 1 h tier is an Ontario addition, and it changes the answer against the national default of 30 min for "any other building."

Difference 11 — manual stations, 3.2.4.16: Ontario harmonized, then extended

This article shows the 2024 Code doing both things at once.

First, Ontario moved toward NBC. Ontario's Sentence (1) is now identical to NBC's:

a manual station shall be installed in every floor area near (a) every principal entrance to the building, and (b) every exit

The revoked O. Reg. 332/12 said "near the principal entrance to the building, and near every required exit." Dropping "required" and going to "every exit" broadens the requirement — and it is Ontario harmonizing to the national text, not diverging from it. That is the 1,730-variations project visible in a single sentence.

Then Ontario adds five sentences NBC does not have. Sentences (5) through (9) cover:

• helicopter landing areas
• hotel reception
• manual stations in apartment units, with the sign reading FIRE ALARM MANUAL STATIONS LOCATED IN APARTMENT UNITS
• key-switch manual stations in impeded egress zones

And one small wording difference runs the other way. NBC's Sentence (2) says "hotel or motel." Ontario says "hotel."

Difference 12 — two-way voice communication, 3.2.4.22: a different title

Same article number, different name.

The Ontario title describes the technology. The national title describes the building class it applies to. If you are searching a PDF by article title rather than by number, you will not find the same article in both documents.

Where Ontario and NBC agree

A comparison that reports only differences is worth less, because you cannot tell whether the author looked at the matches. We did.

One-way voice communication, 3.2.4.23.(1) — word for word identical in both:

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.

No Ontario amendment. Two-stage plus an occupant load over 1 000, with those two occupancy exceptions, gets a one-way voice system in either jurisdiction.

Referenced editions agree too. Both codes reference the 2019 editions of CAN/ULC-S524 and CAN/ULC-S537 in Article 3.2.4.5.

Referenced standards: what is in Ontario's Table 1.3.1.2

Ontario's Building Code references seven ULC standards relevant to this trade:

Standards that appear nowhere in either Compendium volume: S527, S528, S529, S530, S536, S552, S559, S573.

That list surprises people, S536 most of all. S536 is a Fire Code instrument, referenced in O. Reg. 213/07 Table 1.2.1.A — not a Building Code reference. Annual inspection and testing duties live under the Fire Code, which is a separate regulation with a separate reference table. The split between the two regimes is set out in verification vs annual inspection.

The reference rows themselves differ slightly. NBC's S524 row cites more provisions than Ontario's, including Appendix A-notes and 3.2.4.20.(7) and (8). Ontario drops the A-note cross-references, and adds 3.2.4.20.(10) to its S537 row.

Neither code puts a number on intelligibility

We searched both Compendium volumes — 2,261 pages — for "Common Intelligibility" and for "CIS". Zero hits. Zero in the revoked O. Reg. 332/12 as well.

What the Code actually requires, in Articles 3.2.4.22.(1)(b) and 3.2.4.23.(2)(b), is that messages be "audible and intelligible in all parts of the building." That is the entire performance standard, in both jurisdictions.

Appendix A Note A-3.2.4.22.(1)(b) explains what intelligible means: that a person of average hearing and cognitive ability can understand the messages. It goes on to say there is no absolute measure to predetermine the effect of loudspeakers, and that once a building is furnished and occupied it may be necessary to add loudspeakers. It cites ISO 7731 as suggesting a level at least 15 dBA above ambient.

So a numeric intelligibility target on your project comes from CAN/ULC-S524 or from the specification. It does not come from either building code.

The same goes for 520 Hz. Ontario 3.2.4.18.(6) requires that audible signal devices in sleeping rooms in a building of residential or care occupancy "emit a low frequency signal" — and states no frequency. The only figure anywhere near it is the non-mandatory Appendix A note at Vol. 2 page 42, giving a range of 470 Hz to 570 Hz. 520 Hz appears nowhere in Ontario law. It is the NFPA 72 figure — an American standard — and it is the centre of that band. It binds on your job only if a specification or a product listing puts it there.

The low frequency requirement is also new in the 2024 Code. The string "low frequency signal" appears nowhere in the revoked O. Reg. 332/12.

What this comparison does not cover — read this before you rely on any of it

Everything above is the January 16, 2025 Compendium. Four amendment-document versions have been adopted since — O. Reg. 247/25, 110/26, 119/26 and 242/26 — and the operative one, dated 17 July 2026, is not published. Any difference in this article could have moved. Item 7 in particular is exactly the kind of drafting slip a housekeeping amendment fixes.

This diff covers Subsection 3.2.4 and Article 3.2.7.8 only — fire alarm and detection systems, plus emergency power. It is not a complete Ontario-versus-NBC comparison, and nothing here should be read as saying the rest of Part 3 matches.

Anything inside CAN/ULC-S524, S531, S536 or S537 is paywalled and is not covered. We are not going to guess at the contents of a standard we cannot lawfully reproduce. Device spacing, measurement procedure, verification method — all of that lives in the standards, not in either code.

How to check any of this yourself

1. Download NBC 2020 First Printing from the NRC Publications Archive. Free, no registration.
2. Download Compendium Vol. 1 and Vol. 2 from Publications Ontario. $0.00. Division B Subsection 3.2.4 is in Vol. 1; the Appendix A notes are in Vol. 2.
3. Open both to Subsection 3.2.4 and read across. That is the whole method. There is nothing clever about it.
4. Email Ontario.Amendment.Document@ontario.ca for the 17 July 2026 amendment document when a specific number has to be right.
5. Ask your AHJ on anything unresolved — the maximum in item 7 and the care occupancy scope in item 6 above all.

Last updated: August 2026. Code text quoted from the 2024 Building Code Compendium, January 16, 2025 Update (Containing O. Reg. 5/25), compared against NBC 2020 First Printing. O. Reg. 163/24 consolidation period July 22, 2026 to the e-Laws currency date of August 12, 2026; last amendment O. Reg. 242/26. The Ontario Amendment Document in force is dated 17 July 2026 and is not published online.

General information, not compliance advice. Confirm against the code text in force for your project and with your authority having jurisdiction.