Passive fire protection systems are integrated into the design of a building to compartmentalize fire areas (created by assemblies as defined by fire and building codes) to restrict the spread of fire and smoke.

In most of today’s modern commercial or multi-family residential construction, there will be joints between rated construction assemblies which creates a void, or break, in the fire-resistive continuity. Accordingly, per the 2015 National Building Code (NBC), “the continuity of a fire separation where it abuts against another fire separation, a floor, a ceiling or an exterior wall assembly is maintained by filling all openings at the juncture of the assemblies with a material that will ensure the integrity of the fire separation at that location.”

The Canadian fire test standard, CAN/ULC-S115, produced by Underwriters Laboratories of Canada ("ULC"), is used to provide fire resistance ratings to materials or assemblies of materials that provide continuity of fire separations at discontinuities (i.e. joints). Using a tested and listed joint system will help ensure the integrity of the fire separation at each location. This article discusses the ratings and test conditions specified by CAN/ULC-S115 for interior rated joint systems.

Types of Joints

Due to the variety of joint types occurring in construction, ULC addresses joint firestop systems using alpha-numeric categorization. The alpha portion of the listing defines the type of joint (location of joint) and the joint’s ability to move or not. In conjunction, the numeric portion addresses the joint width. The following codes are used for the alpha and numeric portions of the listing:


CAN/ULC-S115 “Standard Method of Firestop Tests of Firestop Systems”

According to the NBC (2015) Section A.3.1.8.3.(4) “The continuity of a fire separation where it abuts against another fire separation, a floor, a ceiling or an exterior wall assembly is maintained by filling all openings at the juncture of the assemblies with a material that will ensure the integrity of the fire separation at that location.”

CAN/ULC-S115 provides the standardized fire test method by which the filling material for firestop joints must be assembled and tested for the desired ratings. Under the requirements of CAN/ULC-S115, a joint system is subjected to a controlled standard fire test to achieve specified temperatures throughout a specified time period. The specified time-temperature curve to be followed is per the requirements found in CAN/ULC-S101 “Fire Endurance Tests of Building Construction and Materials”.   

Time-Temperature Curve

Figure 1: ASTM E119 Time-Temperature Curve

Per CAN/ULC-S115, joint systems installed in walls may be exposed to fire from either side if the installation is symmetrical on both sides of the wall. Wall assemblies where the joint firestop system is asymmetrical must be independently tested from both sides, with the reported fire rating being whichever side provides the lowest rating. Joint systems installed in floor or floor/ceiling assemblies are exposed to fire from the underside. The fire test furnace is maintained at a minimum positive pressure of 2.5 Pa, to simulate the positive pressure produced during a compartment fire.

Ratings Per CAN/ULC-S115

Per CAN/ULC-S115, one of five ratings may be established for each firestop system, depending on which test criteria achieved a “pass”, also depending on whether the optional hose stream and air leakage tests were even conducted:

• Fire Rating (F-rating) - based upon flame occurrence on the unexposed surface.
• Fire and Temperature Rating (FT-rating) - based upon a temperature rise criterion and flame occurrence on the unexposed surface.
• Fire and Hose Stream Rating (FH-rating) - based upon flame occurrence on the unexposed surface and satisfactory performance during the hose stream test.
• Fire, Temperature, and Hose Rating (FTH-rating) - based upon a temperature rise criterion, flame occurrence on the unexposed surface and satisfactory performance during the hose stream test.
• Air Leakage Rating (L-rating) - based upon the volume of air flowing, per unit of time, through the openings around the test specimen under a specified pressure difference.

To achieve a F-rating in accordance with CAN/ULC-S115 the firestop joint system shall prohibit the passage of flame, or the occurrence of flaming (i.e., transient flaming, flash flaming, flickering or substantial flaming) on any element of the unexposed side of the firestop system.

Should a crack, hole or fissure occur during the fire test, it is to be checked for passage of flame and hot gasses using a cotton pad in a wire frame provided with a handle.

The cotton pad is applied to the non-exposed side of the joint when a crack or hole is observed in the joint firestop system. This test involves holding the cotton pad approximately 25mm from the breached surface on the joint assembly for 30 seconds. If ignition (i.e. glowing or flaming) of the cotton pad occurs, it is terms for immediate failure. Should charring occur, a secondary unused cotton pad shall be employed to confirm integrity.

To achieve a FT-rating the F-rating shall be achieved per methods described above. Additionally, T-rating must be achieved using thermocouples placed on the unexposed side of the assembly in accordance with CAN/ULC-S115.

The transmission of heat through the firestop system shall not raise the temperature of any thermocouple on the unexposed surface of the firestop system more than 181 °C above its initial temperature.

To achieve a FH-rating the F-rating shall be achieved per methods described above. Additionally, the joint system shall withstand the hose stream test shortly after termination of the fire test without developing any opening that permits a projection of water from the stream beyond the unexposed surface.

The hose stream test is applied for a duration and pressure determined by the hourly rating in which the joint system is being tested for.

To achieve a FTH-rating, the criteria for F-rating, FT-rating, and FH-rating shall be achieved per methods described above.

If a joint system is to be reported as a dynamic joint system, meaning it is suitable for accommodating compression and extension due to the relative movement of the assemblies on each side of the joint, the assemblies are required to be cycled per CAN/ULC-S115.

For dynamic joints, all joint systems are cycled through their intended specified movement ranges based on wind, thermal, and live load movement. Each cycle involves movement of the joint system through its entire range. Cycling consists of 500 movement cycles at a minimum cycling rate of 10 movement cycles per minute. The test sponsor can additionally request pre-fire-test joint cycling of 30 cycles per minute for 100 cycles, which is theorized to represent seismic cycling. After the system undergoes this treatment, it is subjected to the fire test while extended to its maximum joint width.

L-rating

In addition to the ratings mentioned above, a joint system may optionally be tested for an air leakage rating (L-rating) to CAN/ULC-S115. This additional rating may be required by project-based specifications or requirements.

L-ratings provide an added level of safety to the occupants by quantifying the ability to limit the spread of smoke and toxic gases (smoke seal). An L-rating is an air leakage test rating, measured in liters per second per meter (L/s·m) for joints (or CFM/lin ft when reported in Imperial units). 

L-ratings are determined by measuring how much air will flow through a firestop system when a pressure difference of 75 Pa (0.30 inches of water) is applied across the test assembly. This test is conducted at both ambient air temperature, to simulate cold smoke that would originate from a fire a distance away from the firestop system. It is also conducted at 204°C (400°F), to simulate warm smoke that would reach the firestop system from a fire that could be in near proximity to the firestop system.

Summary
Passive fire protection systems are integrated into the design of a building to compartmentalize fire, smoke, and toxic gases during the event of a fire. To help ensure compartmentation, continuity is maintained when joints are located within or between fire-resistance-rated assemblies, joint systems should be selected that will restrict the passage of fire for a time period not less than the required fire-resistance rating of the assembly(s). CAN/ULC-S115 provides a recognized test method to quantify the fire resistance rating of these fire-resistant joint assemblies. The ULC online listing directory provides a convenient and extensive repository of tested systems that can be specified to help ensure that the code-mandated continuity of fire separations is achieved in practice.

It is important to understand the joint system ratings that can be achieved by tests conducted in accordance with CAN/ULC-S115. The F or FT ratings will ensure continuity of a fire separation. The movement capabilities published as part of system listings will allow a match to the anticipated joint compression and extension. System L-ratings, when available, can additionally allow specification of joint systems that will also provide measurable degrees of air tightness, to further ensure hindrance to smoke spread.

For firestop solutions for a variety of applications, visit the Hilti Fire Protection Design Center:
US: www.hilti.com/firestop
CA: www.hilti.ca/firestop