Under the 2020 National Building Code of Canada (NBC) and related provincial codes, combustible pipes (such as ABS, PVC or PEX) are permitted to pass through fire-rated walls, floors, or floor/ceiling assemblies however there are conditions that must be followed:

General Rule

Combustible piping is allowed, but:
·        The firestop system must be tested to CAN/ULC-S115, the standard for firestop systems in Canada.
·        It must achieve a fire-resistance rating equal to that of the assembly it penetrates.

Example: A ULC-listed firestop system like ULC F-A-2025 is approved for use with combustible pipes penetrating rated floor assemblies.

Additional Requirements for Buildings Over 3 Storeys

In taller buildings (more than 3 storeys), there’s an extra testing requirement. The firestop system must pass the CAN/ULC-S115 fire test with a much higher pressure differential of 50 Pascals (Pa). For comparison, firestop systems for other types of penetrants are typically tested at 2.5 Pa.

Why 50 Pa? Understanding the Stack Effect
1.    The Canadian code requirement for a higher firestop test pressure differential is not caused by the fire dynamic (not fire-driven pressure like from flames or smoke expansion). Instead, it's from the stack effect, a normal condition in tall buildings.
What Is Stack Effect (Chimney Effect)?
1.   Stack effect happens when there’s a temperature difference between indoor and outdoor air.
2.   Warm air is lighter and rises, this creates a pressure difference from bottom to top. This pressure difference can reach or exceed 50 Pa, especially in tall buildings during cold weather.

Why Is This Important in NBC 3.1.9.5?

The code requires that a firestop system for most combustible piping penetrations must functional even with a  50 Pa pressure differential. This will account for the possible stack effects that could occur when a multi-storey combustible pipe melts or burns open on the floor exposed to fire.

Since the NBC enumerates the cases where a 50Pa firestop is required based not only on the pipe combustibility but also based on what the pipe is used for, it’s worthwhile to mention that combustible electrical conduits are not required by code to have 50Pa firestops. They still need firestopping tested to CAN/ULC-S115, but the normal firestop pressure of 2.5Pa is all that’s required. 

Summary

·        For buildings over 3 storeys, the 50 Pa pressure mentioned in NBC 3.1.9.5 is needed for specific uses of combustible pipes and tubes.
·        Not all combustible materials require the 50 Pa test, electrical conduits are exempt, unless otherwise specified.

References

For more information, please contact your local Hilti experts or go to Hilti online
1.   To learn more about CAN/ULC-S115 for interior rated joints, check out: Understanding Standard Method of Fire Tests of Firestop Systems
2.   For information about firestopping guidelines used in the NBC 2020, watch: NBCC Requirements Related to Firestopping
3.   To check out Hilti’s Firestop portfolio, visit: Firestop Design Center - Hilti Canada