FIRE DOOR PRODUCTS
Intumescent and Smoke Seals
Intumescent and smoke seals close the gap between door and frame in a fire. They are also the single most common thing we find wrong on inspection. Supplied and fitted to the correct specification.
WHAT IT IS
Intumescent and smoke seals: two seals, two jobs
Fire doors use two kinds of seal, often combined in one strip. Intumescent seals sit in a groove in the door edge or frame and stay dormant until heated. Then they expand to many times their size, closing the gap between door and frame to maintain the compartment. Cold-smoke seals (a brush or fin) work at ordinary temperatures. They hold back the cool smoke that spreads first and harms people most. A combined intumescent-and-smoke seal does both. Approved Document B sets out where doors need smoke seals.
WHAT IT DOES
It closes the gap fire needs
For a fire door to hold its rating, the perimeter gap has to close as the fire develops. That is the intumescent seal’s job. Before that, in the early minutes, the smoke seal stops smoke slipping through the edges into the escape route. The seal has to be the right size and type for the door and its gaps. Too small, and it cannot bridge the gap. The wrong specification, and it may not perform the way the door did in its fire test.
WHY IT MATTERS
Intumescent and smoke seals: the biggest single failure point
Across the fire doors we inspect, seals are the most common thing we find wrong: missing, perished, damaged, painted over or simply the wrong size. However, they are also one of the most straightforward things to put right. That makes them a quick win on the road to a compliant door. Our fire door gaps guide explains how seals and gaps work together.
WHAT WE FIND ON INSPECTION
Where intumescent and smoke seals fall short
Missing or removed. No seal at all, or a section that has fallen out or gone missing.
Perished or damaged. Seals that have hardened, split or torn after years of use.
Wrong size or type. A seal too small for the gap, or an intumescent-only seal where the door needed a combined smoke seal.
HOW WE HELP
Supplied and fitted correctly
We supply and fit correct-specification intumescent and smoke seals, sized to the door and its gaps. That can be part of an installation, or remedial works from your inspection report. Either way, we record the work, so you hold the evidence.
FAQ
Common questions
What’s the difference between intumescent and smoke seals?
Intumescent seals expand in heat to close the door-to-frame gap and maintain fire integrity. Smoke seals (a brush or fin) block cool smoke at ordinary temperatures. Many doors need both, often as a combined seal.
Do fire door seals need replacing over time?
Yes. Seals perish, harden and suffer damage with use. So we check them at every inspection and replace them when they are no longer sound, which keeps the door performing as tested.
Is it OK to paint fire door seals?
Best avoided. Paint build-up can stop an intumescent seal expanding and clog a smoke-seal brush. If someone has painted over the seals, they usually need replacing.
GET A QUOTE
Need seals checked or replaced?
Ask us to inspect, or send your report. We will then quote to put the seals right, clearly itemised, with no obligation.