In passive fire protection, the annular gap — the space between a service (such as a pipe, cable or duct) and the wall or floor it penetrates — may appear insignificant, but its proper treatment is vital. Under AS 4072.1, this gap must be sealed with an approved, tested firestop system to maintain the Fire Resistance Level (FRL) of the surrounding barrier.
When a service penetration breaches a fire-rated wall or slab, it creates a path for heat, flame, and toxic smoke. Even a 10mm void can compromise the integrity of the compartment. The annular gap is especially important because different services expand or contract in fire, and air pressure changes can force hot gases through unsealed spaces.
AS 4072.1 mandates that:
- Firestop systems must be tested to AS 1530.4 using the exact combination of service and substrate.
- All gaps must be sealed using an approved fire-rated sealant, mastic, wrap, or mechanical closure (such as a fire collar).
- The installation must replicate the tested configuration — including gap width, depth, and orientation.
At Ceasefire PFP, annular gap compliance is treated as a fundamental life-safety requirement. Our technicians are trained to accurately measure and prepare each opening, and to select firestop systems that will perform reliably under fire conditions. We only install products with proven expansion characteristics and verified fire test results.
For example, an intumescent mastic might expand 20 times its original volume, enough to seal a 30mm gap around a cable bundle. But if used in the wrong orientation, or without sufficient backing material, it could fail under load. Ceasefire uses high-density backer rods and depth gauges to control sealant application.
We regularly encounter penetrations where the annular gap has been filled with acrylic or polyurethane sealants — materials that appear similar to firestop products but offer no fire resistance. Our inspectors flag these defects and provide recommendations for certified replacements.
Poor annular gap sealing is one of the top five reasons projects fail fire safety audits. It can delay occupancy certificates, invalidate warranties, and put lives at risk. It also reflects poorly on the builder’s commitment to compliance.
Ceasefire PFP prevents these issues by:
– Using systems with wide annular gap tolerance (e.g. 5–50mm)
– Photographing every penetration pre- and post-sealing
– Logging each installation in our Passive Fire Register
– Including gap width and product reference in our compliance packs
In summary, annular gap compliance is not a technicality—it’s a life safety measure. Ensure your firestopping meets the full intent of AS 4072.1 by engaging professionals like Ceasefire PFP, who take every millimetre seriously.
