Fire stopping systems in commercial buildings

To understand your responsibilities re fire stopping of service penetrations, check the Building Code of Australia (BCA). In simple terms, the BCA says that the penetration should not reduce the required Fire Resistance Level (FRL) of the penetrat-ing element itself; i.e., the fire rated wall, floor or ceiling.

The FRL is a grading period in minutes determined in accordance with AS 1530 Part 41 for (a) structural adequacy, (b) integrity and (c) insulation. The Fire Resistance Level is expressed in that order (e.g. FRL = 120/120/60)

Electrical fire stop systems

For a particular proprietary fire stop system, it is not practical to fire test every configuration and propri-etary brand of conduit, cable and cable tray in commercial buildings. However, AS4072 Part 12 provides for a standard fire resistance test configura-tion for electrical and communication cable systems (most commonly occurring PVC-insulated and sheathed power and telecommunications cables with copper conductors), and is deemed to be approved for most configurations. Limitations are given in that Standard, and specific fire testing is required for electrical penetrations falling outside of the coverage provided by the standard test configuration. 

 

Electrical fire stop systems

Generic forms of fire stop for electrical service penetrations.  Most generic forms of fire stop systems can provide an FRL rating. Your choice will be determined by the specific application and additional requirements such as whether the penetration is temporary or permanent, whether re-routing is expected, the required movement capabilities, environmental conditions, expo-sure to oils and grease, and, of course, the infamous budgetary constraints. 

Mortars

These are generally a gypsum- or cement-based powder blended with inorganic lightweight fillers, composite reinforcement and chemical modifiers. The mortars are designed to be mixed with water and then poured around and between penetrating services. Note – Standard concrete will not provide adequate fire resistance without expensive and cumbersome steel reinforcing. 

Sealants/Mastics

Typically, single pack systems comprise organic, inorganic or intumescent fillers pre-dispersed in a suitable binder (acrylic, polyurethane or silicone). The materials are of high viscosity and dispensed by a gun or trowelled into the opening and between penetrating services 

Note – Intumescence is a characteristic of certain fire barrier products that expand to many times their original volume when exposed to heat, filling penetrations and forming a hard and resilient char.

Putties

These single pack materials are similar to some sealants/mastics, but are capable of being formed and directly installed by hand.

RTV Silicone foams

Room Temperature Vulcanising (RTV) foams are two component silicone materials which, when mixed together, cause the materials to foam and increase its volume.

Pillows/bags

Pillows and bags are made from special fabric and enclose a non-combustible filling of mineral wool or similar, often incorporating intumescent material. They come in various sizes and shapes and

Electrical fire stop systems

are stacked into the penetration opening, tightly encapsulating the penetrating electrical services. They were originally introduced for temporary or high traffic penetrations but are the simplest form of fire stopping system and are widely used where more cost-effective and reliable systems should be employed.

Note – Some facility managers have concerns over the ease of removal of pillows or bags and do not allow their use in their buildings with a preference for a more permanent solution.

Blocks/bricks

Blocks and bricks are made from bonded vermiculite, modified rubber, polyurethane or flexible intumescent material They can be in many shapes and sizes, but are typically shaped like conventional bricks and are stacked in the penetrating opening similar to laying conventional bricks, but without the need for a mortar.

Boards

There are many types of fire-resistant board materials, including fibre reinforced autoclaved calcium silicate, vermiculite bonded sodium or potassium silicate and other composite proprietary intumescent board systems. The board needs to be cut to fit around electrical services penetrating the opening. Boards are typically used where large penetrations are present and often require the use of additional fire stop products (see Composites below).

Mineral wool and fibre slabs

Mineral wool/fibre are typically supplied as slabs or batts coated with an intumescent fire resisting intumescent coating. Like boards they need to be cut to fit around electrical services penetrating the opening. They also are typically used where large penetrations are present and often require the use of additional fire stop products (see Composites below).

Composites

Sometimes a combination of fire stop products are used together to form a composite system. An example might be a board and some additional pillows and sealant mastic or putty.

Note – Mixing and matching product from different manufactur- ers/suppliers will usually invalidate fire-testing approvals. John Rakic is the principal of J-RAK Consulting and is considered to be an expert on Passive Fire & Smoke Containment issues. He represents Australia on ISO and local Australian Standards’ technical committees in this field.

He is National Technical Convenor for the Fire Protection Association Australia’s TC18 committee on Passive Fire Protection, and the Passive Special Interest Group, and is the founder of the Alliance for Passive Fire & Smoke Containment. www.rakman.com.au or email [email protected]