Date of Publication: August 19, 2025 [2022.11.V-02.C]
Subject: Requirements for Walls Used to Create Smoke Travel Distance.2024 OBC UPDATE
Summary of updates: No Changes to references or recommendations.
2024 Ontario Building Code [O.Reg 163/24 Amended to 5/25] Reference(s):
Sentence 3.3.1.4.(4)(a)
Article 3.3.1.5.(1) and (2)
Functional statements for Sentence 3.3.1.5.(2):
F05: To retard the effects of fire on emergency egress facilities.
F10: To facilitate timely movement of persons to a safe place in an emergency.
Incoming Request:
A suite located in a multi-storey Part 3, sprinklered building is undergoing an extensive renovation. The suite is served by a public corridor which is not separated from the suites, as permitted by 3.3.1.4.(4)(a), however the suite is of sufficient size that 2 egress doors are required as per 3.3.1.5.(1) and (2). The proposed design shows unrated drywall partitions that serve to distance the two egress points from one another to comply with sentence 3.3.1.5.(1) and (2). The partitions terminate at a typical unrated acoustic tile ceiling.
Is this compliant with the OBC? See the sketch below.
Where an assembly (typically an interior non-rated drywall partition) has been constructed to create an acceptable “smoke travel distance” as referenced in Sentence 3.3.1.5.(2), is this assembly required to terminate at the floor or roof above?
Executive Summary:
An acoustic tile ceiling may be considered as part of an assembly designed to direct or delay the movement of smoke (a “smoke partition”) when properly detailed and installed.
Discussion & Considerations:
Article 3.3.1.5.:
The purpose of Article 3.3.1.5. of Division B of the Ontario Building Code (the OBC) is to ensure that when 2 egress points are required from a suite or room, they are distant enough from each other that if one egress is impeded due to smoke of fire, the other egress will remain accessible.
Sentence (2) recognizes that a proposed design may include 2 egress doors that are close to one another in plan, but function as two distant egresses due to interior walls and/or ceilings constructed between the two egress points that will inhibit the travel of smoke from one egress point to the other.
It is important to note that the Code does not require this assembly to be constructed as a fire separation or have a rating. It is not meant to contain smoke (as a “0 rated” partition would be), but only to direct or delay the movement of smoke. This type of construction may be known as a “smoke partition” in some jurisdictions.
A properly constructed, tight fitting acoustic tile and T-Bar ceiling would appear to fit this category, with caveats.
Principles of Smoke Movement:
It is important to also remember that smoke that originates from a fire almost always rises due to hot combustion gasses at its origin. Smoke from a fire that has drifted away from its heat source will move with the air currents within the building.
In the case of smoke that has originated from a fire near one egress point, and has penetrated through the acoustic tile ceiling on one side of a smoke partition due to the hot gasses associated with the fire, the likelihood of the smoke then migrating back down through an acoustic tile ceiling directly at the other egress point are very remote.
Overall Building Design:
Finally, we have to keep in mind the overall fire separation requirements of the suite and the building. Due to the overall building design (sprinklered, exits within 45 m, D occupancy, etc.), the suite does not require any fire separations within it, and the suite to public corridor wall is not even required to be a separation. In this building requiring even 0 rated walls between two egress points within a suite seems counterintuitive.
Risk/Benefit Analysis:
An Ontario building official may want to consider the following points when evaluating construction meant to delay or direct smoke.
- Building classification:
- The same requirements for all materials will extend to smoke partitions, i.e. combustible/non combustible, smoke developed/flame spread rating, etc.
- Resistance to mechanical damage/alteration:
- Materials must stay in place during normal building activities for them to be effective.
- Certain types of acoustic tile ceiling systems are more smoke-tight than others:
- Heavier tiles are better.
- Larger panel sizes require fewer components and joints.
- Overall tightness of assemblies:
- Typical construction materials (caulking, specific trim pieces) can be used to increase the effectiveness of the assemblies.
- Openings in ceiling directly adjacent to either of the egress points:
- Ceiling openings and penetrations (recessed lighting, return air openings, architectural features) should be limited in these areas.
Final Recommendation:
Construction that is intended to direct or delay movement of smoke for the purposes of conforming to Sentences 3.3.1.5.(1) and (2) does not need to be constructed as a fire separation. Construction may consist of materials permitted by the OBC for the building classification with attention paid to tight-fitting construction and installation.
Recommendation to Ministry of Municipal Affairs and Housing:
None at this time.
Referenced Documents:
- 2024 Ontario Building Code:
- Sentence 3.3.1.4.(4)(a)
- Article 3.3.1.5.(1) and (2)
- Functional statements for Sentence 3.3.1.5.(2):
- F05: To retard the effects of fire on emergency egress facilities.
- F10: To facilitate timely movement of persons to a safe place in an emergency,
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.