Intumescent Seals is a division of Dixon International Group Limited


There is often a requirement for a ventilation aperture to be made in a fire compartment wall or fire door within such a wall. This penetration breaches the integrity of the building element and so it is necessary to maintain the required fire resistance as well as the necessary ventilation. The THERM-A-GRILLE intumescent air transfer grille enables this two-fold requirement to be met.


THERM-A-GRILLE is an intumesent air transfer grille consisting of two sheets of steel mesh coated with a graphite based intumescent material, all retained in a lightweight frame. THERM-A-GRILLE provides free air flow through the unit over approximately 50% of the face area. The intumescent coating activates at approximately 180°C and expands to fill the ventilation holes in the grille thus providing the required fire resistance. The twin plate construction of THERM-A-GRILLE provides fire insulation performance in addition to fire integrity.


THERM-A-GRILLE is suitable for vertical apertures in fire resisting doors and compartment walls. It is held in position by means of 50mm No.8 size steel screws (not supplied) through the unit’s frame at 150mm centres. THERM-A-GRILLE is fitted centrally within the aperture. Where the wall includes a cavity e.g, plasterboard/timber stud partitions then the aperture must be lined with fire resisting material e.g. a steel sleeve to the full depth of the aperture. Apertures in fire resisting door leaves should only be formed by suitably qualified door converters to ensure that the fire integrity of the door is not compromised. Facia or louvre plates (not supplied as standard) may be fitted to either side of the aperture.


THERM-A-GRILLE will provide fire resistance of up to 60 minutes as part of a suitable fire resisting door or compartment wall.



THERM-A-GRILLE is available in square and rectangular sizes from 50mm x 50mm up to 600mm x 600mm. All THERM-A-GRILLE units are 38mm thick.

Test Evidence

THERM-A-GRILLE meets the performance requirements noted above in accordance with BS476:part 20. It is currently being evaluated to the requirements of BS EN 1366

Copies of test reports are available on request.

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