Fire alarm cable in Canada: what the electrical code and CAN/ULC-S524 actually require

Last updated: September 2026

Quick answer

• Copper conductors, insulation rated not less than 300 V. Ordinary Class 2 control cable is often rated lower and will not pass.
• Minimum No. 16 AWG for individual conductors pulled into a raceway, No. 19 AWG for individual conductors laid in a raceway, and No. 19 AWG for an integral assembly of two or more.
• Conductors must be entirely independent of all other wiring, and must not enter a raceway, box or enclosure occupied by other wiring.
• The circuit is treated as Class 1 even at 24 V, because a fire alarm is a safety control device.
• The cable is built to CSA C22.2 No. 208, which is where FAS, FAS 90 and FAS 105 on the jacket come from. Maximum 300 V, minimum 60 °C.
• The flame rating is a CSA FT number, not an American CMP or CMR. FT6 is the Canadian plenum grade.
• Where a circuit has to survive fire, the Ontario Building Code points at CAN/ULC-S139 and a 1 h circuit integrity rating, or a 1 h fire separation instead.

Which document governs which part of the job

Three documents touch a fire alarm cable pull, and mixing them up is the most common reason a job gets argued about on site.

The Building Code is what makes you install a system at all, and it is the document that names the ULC standards. On how the two codes divide up, see Building Code versus Fire Code in Ontario.

CAN/ULC-S524 governs the design and installation of the system itself: circuit classes, supervision, zoning, device placement, what a fault has to do. Its scope covers both code-required and voluntary installations. The current published edition is CAN/ULC 524:2024, the 8th edition, but the codes in force still reference the 2019 edition, and that distinction matters more than people expect. See which edition applies.

The Canadian Electrical Code, Part I, Section 32, governs the wiring method and the conductors. In Ontario it is adopted as the Ontario Electrical Safety Code. The 2024 OESC came into force 1 May 2025, it is the 29th edition, and it contains the 26th edition of the Canadian Electrical Code, Part I, plus Ontario-specific amendments. Some sources, ESA's own pages included, call it the 28th edition; the OESC glossary entry settles the number and explains where the confusion comes from.

So: the Building Code tells you a system is required, S524 tells you how the system goes together, and Section 32 tells you what wire you are allowed to put in the pipe. An inspector on one of those documents cannot sign off the other one.

The conductor rules you have to hit

These are the numbers to have in your head before you order anything. Fire alarm conductors are copper, with ampacity adequate for the circuit, and an insulation rating of not less than 300 V. Optical fibre is permitted as an alternative.

Minimum sizes split three ways, and the split is about how the conductor gets into the raceway:

• No. 16 AWG for individual insulated conductors pulled into raceways
• No. 19 AWG for individual insulated conductors laid in raceways
• No. 19 AWG for an integral assembly of two or more insulated conductors

The logic is mechanical. A conductor dragged through a pipe takes tension and abrasion that a conductor laid into a trough never sees, so it has to be heavier. An assembly gets the benefit of its own jacket.

Source note. The three sizes are cited to Rule 32-100(4) by Ark Tsisserev in IAEI Magazine's Canadian Perspectives column, Summer 2025. The copper, 300 V and raceway-sizing elements are independently corroborated by William Burr's road map to Section 32 of the 26th edition of the CE Code in Electrical Industry News Week. Both are Canadian-authored secondary sources; the code text is paywalled and we did not read it. If you are putting a rule number into a compliance document, check it against your own copy of the OESC.

A practical point follows from the 300 V rating: the general-purpose 18/2 and 16/2 control cable on the van from another trade is frequently rated below it. It is not fire alarm cable in Canada, however convenient, and swapping it in is a deficiency an inspector will find without trying.

Why a 24 volt circuit is treated as Class 1

Everything about a fire alarm initiating circuit invites you to treat it as low voltage you can run loosely. It is 24 V, and it draws milliamps. In most other trades that would be the end of the analysis.

The Canadian code closes that door explicitly. Rule 16-010 requires that a circuit supplying a safety control device, where failure of that device would introduce a direct fire or life hazard, be deemed a Class 1 circuit regardless of the voltage or whether the supply is power limited. A fire alarm system is exactly that kind of device.

None of the relaxations you would reach for on a Class 2 circuit are therefore available. Not the lighter wiring methods, not the loose separation, not the smaller conductors. This is one of the sharper divergences from American practice, where fire alarm circuits are commonly installed as power limited under a different rule set entirely. American guidance on power limited fire alarm cable does not transfer here, and we treat that divergence at length in NFPA 72 versus CAN/ULC-S524.

Permitted wiring methods under Section 32 are, in summary: totally enclosed metal raceway, cable with metal armour or a metal sheath, rigid non-metallic conduit, and electrical non-metallic tubing embedded in masonry or concrete. The theme is mechanical protection.

Reading the jacket: FAS, FT and what listing means

Canadian fire alarm cable is built to CSA C22.2 No. 208, Fire alarm and signal cable, currently C22.2 No. 208:18. Its scope, published openly by the Standards Council of Canada, covers single and multiple conductor fire alarm cables with a maximum nominal voltage rating of 300 V and a minimum temperature rating of 60 °C, and defines five construction types:

FAS, FAS 90, FAS 105, FAS 150 and FAS 200.

The number is the temperature rating in degrees Celsius, so FAS 105 is 105 °C rated cable, and it is what you will see most often on Canadian jobs. There is nothing magic about the 105: it is not a fire survivability rating, it is not a riser rating, and it tells you nothing about flame spread.

Flame spread is separate and appears as an FT marking. On a Canadian jacket you should be able to read, in some order: the type designation (FAS 105), the voltage rating (300 V), the conductor count and size, the FT rating, and a certification mark.

That certification mark is what "listed" means in practice. The cable has to be certified by a body accredited by the Standards Council of Canada, and the mark on the jacket is the evidence. A US-only UL mark is not a Canadian certification: see ULC versus UL in Canada. If the jacket carries no Canadian mark it does not go in the building.

Riser and plenum, and why the American names do not map

If you have come from American supply catalogues you are used to CMP for plenum, CMR for riser and CM for general purpose. Canada does not use those designations. It uses CSA FT ratings, which come from different tests.

FT6 is the Canadian plenum grade. It is the most stringent of the set, and it is what belongs in a ceiling void used as a return air plenum or in any other air-handling space.

The requirement does not originate in the electrical code. It originates in the National Building Code, which restricts materials in air-handling plenums to a flame spread rating not exceeding 25 and a smoke developed classification not exceeding 50, with defined exceptions for qualifying electrical cables and raceways. The CE Code implements that through Rules 2-130 and 2-132. Ark Tsisserev's IAEI column sets that chain out, but his article dates from 2019, so confirm the rule numbers against your current edition.

Canadian Consulting Engineer records that Ontario and British Columbia opted for the more stringent FT6 requirement. Treat that as background, not as your compliance answer, because what counts as a plenum is a building question before it is a cable question. The practical failure is ordering FT4 for a job where the ceiling void turns out to be a return plenum, and finding out after the ceiling is closed.

Shielded or unshielded, and the mistake that costs you a morning

Shielding on a fire alarm job is almost always about data, not the initiating circuit. Twisted shielded pair is typically specified for RS-485 style data buses between a panel and its transponders or annunciators, with power run as a separate pair. Running data and power in one common jacket is a reliable way to generate intermittent faults nobody can find.

Here is what we could not verify, and we would rather say it than guess. We could not locate a requirement in CAN/ULC-S524 or in Section 32 that specifies when a shield is required or how it is to be terminated. The standards are paywalled, and the free Canadian secondary sources we read defer the question to the equipment manufacturer's installation instructions. In practice those instructions are the operative document.

What is not in dispute is the field error. Grounding a shield at both ends creates a ground loop. The shield becomes a parallel path between two points that are not at the same potential, and current circulates through it. The symptoms are exactly the ones that waste a morning: intermittent communication faults on the data bus, a ground fault that appears and clears with no obvious cause, and behaviour that changes when a piece of unrelated equipment on the same building steel switches on.

The same failure happens without anyone grounding anything on purpose, when a drain wire is left long inside a device box and touches the box or a bonded mounting screw. That is one accidental second ground, and it produces the identical symptoms.

The discipline is simple: ground the shield at one end only, normally at the panel, and cut back and insulate the drain wire at every other termination so it cannot find metal. If you are chasing a fault that fits this description, our guide to ground fault troubleshooting walks through isolating it, and the shielded cable entry covers the terminology.

When the cable has to survive the fire

Some circuits are expected to keep working while the building burns, and that is where circuit integrity cable comes in.

In Ontario the relevant provision is Article 3.2.7.10, Protection of Electrical Conductors. Conductors serving certain systems must either conform to CAN/ULC-S139 and provide a circuit integrity rating of not less than 1 h, or run in a service space separated from the rest of the building by a fire separation with a fire-resistance rating of not less than 1 h. Certain mechanical applications call for 2 h instead. There is an important carve-out: fire alarm branch circuits within a storey that connect transponders and individual devices do not have to meet it.

CAN/ULC-S139 is the Standard for Fire Test for Circuit Integrity of Fire-Resistive Power, Instrumentation, Control, and Data Cables. It is a binational standard with requirements identical to ANSI/UL 2196, and it tests cables energised during fire exposure and then hit with a hose stream. The 2017 edition has been superseded by CAN/ULC 139:2025.

Be aware of the limits of what we can tell you here. We read Article 3.2.7.10 in two secondary reproductions of the Ontario Building Code, one presented as the 2024 edition (O. Reg. 163/24) and one as the 2012 and 2017 editions. The substance agrees, but we could not open the free Building Code Compendium to confirm the numbering as it stands in the 2024 Code, so confirm it before you cite it. And where a specification calls for two hour survivability on a fire alarm circuit, that often comes from the specification or the S524 design rather than a Building Code article. Ask which, because the answer changes what you may substitute.

Separation, shared raceways and shared boxes

This is the requirement that produces the most arguments and the most rework. Fire alarm conductors must be installed entirely independent of all other wiring, and must not enter a raceway, box or enclosure occupied by other wiring. The exceptions are the defined connection points: the point of supply, signal, ancillary device and communication circuit connections.

Read that literally, because it is meant literally. It is not "keep them apart where practical". A shared 4 by 4 box with a lighting circuit is a failure. A shared piece of EMT is a failure. A fire alarm cable passing through a junction box that holds line voltage, with no splice made, is still a failure: the rule is about occupancy of the enclosure, not about whether you connected anything.

The inspection failures that follow are predictable:

• Fire alarm cable pulled into a spare conduit that already carries a lighting circuit, because the pipe was there
• A ground fault traced back to a fire alarm conductor abraded against a line voltage conductor in a shared box
• Devices fed from a junction box shared with an unrelated system, found at verification rather than rough-in
• Non-metallic wiring methods installed with no bonding conductor

Where a shared pathway genuinely cannot be avoided, that is a conversation with the authority having jurisdiction before you pull, not a defence after the fact.

Quick reference

Sizing a conductor for the code minimum is not the same as sizing it for the job. On a long notification circuit the governing constraint is voltage drop, not the code minimum, and you size up accordingly.

What we could not confirm

• The Section 32 rule numbers. The requirements are attested by two independent Canadian sources, one of them keyed to the 26th edition of the CE Code. The numbers 32-100, 32-100(4), 32-102, 32-102(3) and 16-010 come from those secondary sources, not from code text we read. Ontario amendments could differ.
• Shielding requirements in CAN/ULC-S524. We could not locate any. The shield practice above is field practice plus manufacturer instruction, not a rule we can cite.
• The article and sentence numbering of the Ontario Building Code circuit integrity provision in the 2024 edition. The substance is consistent across the reproductions we read. The numbering is not confirmed against the 2024 Compendium.
• Whether Ontario mandates FT6 in every plenum space. A Canadian trade source states Ontario and BC opted for FT6. We could not confirm the current provision.

Confirm all of the above with your electrical inspector and the authority having jurisdiction on the specific project. If you are ordering cable for a job where the answer matters, ask before the purchase order, not after the pull.

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