Date of Publication: August 28, 2025 [2022.12.V-02.C]
Subject: Wireless Interconnection of Smoke Alarms 2024 OBC UPDATE
Summary of Updates: Recommendation revised in light of new sentence 9.10.19.5.(2) and conversations with MMAH.
Ontario Building Code Reference(s):
Appendix note to Sub-section 1.1.2. of Division A
Article 9.10.19. of Division B
Appendix note A-9.10.19.5.(2)
Incoming Request:
A homeowner has constructed their own rear and second storey addition. During the occupancy inspection, the building inspector discovers that ‘wireless’ smoke alarms have been installed (in lieu of hard wire connection). The homeowner indicates that the electrician that installed them said they are ‘just as good’ as hardwired/interconnected smoke alarms, and that they have been approved in neighbouring jurisdictions.
Do ‘wireless’ smoke alarms meet the intent of Part 9 of the Ontario Building Code, in the same way as hard-wired smoke alarms?
Executive Summary:
The intent of the 2024 OBC is to permit wireless interconnection of smoke alarms for houses with secondary suites only. However wireless interconnection is recognized by the NBC and the referenced standard. If an AHJ chooses to accept wireless interconnection in other scenarios, an internal policy or alternative solution proposal may be advised.
Discussion & Considerations:
Smoke alarm location:
Since the construction in question is a new addition, the requirements of Sub-section 9.10.19. will apply. If the addition/renovation is configured so that the new floor levels match the existing floor levels, then one smoke alarm on each storey would be sufficient to meet the requirements of 9.10.19.3.(1)(a). This could be provided by existing smoke alarms in the existing part of the house or new alarms in the addition. Where the existing smoke alarms in existing locations are being proposed to be left in place to provide “storey” protection, they would not be required to meet current OBC requirements for visual signaling component, sound patterns, visual signaling component, power supply, and interconnection.
However, if new bedrooms or a hallway have been constructed, (in the addition or in the existing part of the house) additional smoke alarms will be required in the hallway and/or bedrooms to satisfy the requirements of 9.10.19.3.(b). These smoke alarms would be subject to current
requirements of Sub-section 9.10.19.
Where the addition/renovation results in a combination of existing bedrooms and new bedrooms, the new bedrooms must comply with 9.10.19.3.(1) and the existing bedrooms will not require upgrading, although it would be recommended.
Means of interconnection:
2024 OBC Sentence 9.10.19.5.(1) states:
“(1) Where more than one smoke alarm is required in a dwelling unit, the smoke alarms shall be wired so that the activation of one alarm will cause all alarms within the dwelling unit to sound.”
The implication is that the wiring of the alarms is the required means of the interconnection, but more importantly, this sentence only applies to smoke alarms within a single dwelling unit.
Sentence (2) goes on to say:
(2) Smoke alarms in a house with a secondary suite shall be wirelessly interconnected or interconnected by hard-wiring so that the activation of any one smoke alarm causes all smoke alarms within the house with a secondary suite to sound.
This could be interpreted to mean that any of the smoke alarms in a house with a secondary suite can be wirelessly interconnected, (i.e. those within a single dwelling unit or between dwelling units) however the appendix note clarifies that the intent is to limit wireless interconnection to the scenario described in appendix note A-9.10.9.15.(1)
In spite of this clarification, applicants may propose wirelessly interconnected smoke alarms in other scenarios. Currently smoke alarms are available in the Canadian market that meet the CAN/ULC-S531 standard referenced in 9.10.19.1., and accomplish interconnection between smoke alarms using wireless technology, usually a radio frequency (RF) transceiver. When evaluating whether or not wirelessly interconnected smoke alarms meet the intent of 9.10.19.5.(1), a building official should consider the following:
- The 2020 National Building Code of Canada sentence 9.10.19.5.(1) was revised from 2015 to read: “Where more than one smoke alarm is required in a dwelling unit…the smoke alarms shall be interconnected so that the activation of any one alarm will cause all smoke alarms …to sound.” Per the proposed Change 1324, this was done specifically to allow wireless interconnection and recognized that ULC standards include wireless interconnection.
- Sentence 9.10.19.5.(2). was also added to the 2020 NBC, which more explicitly permits wireless interconnection for houses with secondary suites, for the reasons contained in the appendix note A-9.10.19.5.(2)., which is the same as the appendix note in the 2024 OBC.
- The 2024 OBC has retained the wording “…the smoke alarms shall be wired so that the activation of any one alarm will cause all smoke alarms in the dwelling unit to sound.” This implies that wireless interconnection is not permitted.
- CAN/ULC-S531-2019 (referenced by the 2024 OBC) specifies, within the heading “Smoke Alarm Reliability Prediction” that “…integral transceivers and related components used for non-supervised wireless interconnected alarms are required to be included in the reliability prediction…”.
- This same standard requires that a “supplementary signalling feature, such as a transmitter for remote signalling…be compatible with the device…and intended for fire alarm application…”
- 2024 OBC sentence 9.10.19.5.(2) and its appendix note permit smoke alarms in a house with a secondary suite to be wirelessly interconnected or interconnected by hard-wiring.
- Conversations with MMAH staff have indicated that the intent is for wireless interconnection to be used only in houses with a secondary suites where wiring cannot be installed between suites to interconnect the smoke alarms, as described in A-9.10.19.5.(2).
- Where additional smoke alarms are being provided in excess of those required by the Code, or in areas not under construction, they would be considered a “voluntary installation” as described in appendix note A-1.1.2., and wireless interconnection would be reasonable.
Power Supply:
OBC Sentence 9.10.19.4.(1) requires smoke alarms to have a “permanent connection to an electrical circuit”. Smoke alarms powered by battery are only permitted if there is no electrical power to the building.
Risk/Benefit Analysis:
The 2024 OBC permits wireless interconnection, but only in limited and specific circumstances. However these limitations are based on practical construction considerations, not on life safety considerations. If there is a risk that a wireless means of interconnection is unreliable, it appears to be mitigated by the fact that the CAN/ULC-S531-2019 Standard includes the wireless interconnection feature as part of the evaluation. The benefits of allowing wireless interconnection are that it may alleviate construction issues and may encourage applicants to provide interconnected smoke alarm coverage in areas that are not under construction.
Final Recommendation:
The 2024 OBC limits wireless interconnection of smoke alarms to certain applications. Where an AHJ chooses to allow wireless interconnection in situations other than those described in 9.10.19.5.(2)the OBC, an internal policy or an alternative solution proposal is a recommended way to formalize the practice.
It should be kept in mind that smoke alarms meeting CAN/ULC-S531:2019 are one of the least expensive and most effective life safety features in a house. Where an applicant is proposing a design or device that does not appear to meet the requirements or the intent of the Code, a building official should request clarification. Furthermore, where an applicant is proposing a design that “technically” meets the wording and intent of the Code, but misses an easy opportunity to improve smoke alarm coverage and therefore life safety, a building official may want to consider suggesting a voluntary installation.
Recommendation to Ministry of Municipal Affairs and Housing:
The official amendment document appears to indicate that 2020NBC sentence 9.10.19.5.(1) is accepted as written, however the MMAH-provided 2024 OBC .pdf compendium uses different wording as shown above. We urge the MMAH to clarify this.
Referenced Documents:
- 2024 Ontario Building Code [O.Reg 163/24 Amended to 5/25]
- Appendix note to Sub-section 1.1.2. of Division A
- Article 9.10.19. of Division B
- CAN/ULC-S531:2019 Standard for Smoke Alarms
- 2015 National Building Code of Canada:
- Sentence 9.10.19.5.(1) of Division B
- 2020 National Building Code of Canada:
- Sentence 9.10.19.5.(1) of Division B
Disclaimer:
This guidance document is intended to assist building officials by gathering relevant information to interpret the OBC Act and the prescriptive requirements of the Ontario Building Code, and is intended to be a best practice aid for building officials.
The views expressed within this guidance document should not be considered as the official interpretation of legislated requirements based on the Ontario Building Code, as the final responsibility for interpretation rests with the local Authority Having Jurisdiction.
The views of this advisory committee should not be construed as legal advice.