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ISL Brand

ISL Therm-A-Plate | Intumescent Letterbox Liner

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Product Code: LETTERBOX30IS
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It is increasingly common to find that entrance doors to flats and apartments in tower blocks and houses in multiple occupation, are fire resisting to 30 or 60 minutes rating. As these doors are effectively external doors, many have apertures cut in them to serve as letter boxes, but unfortunately this compromises the door leaves integrity.

The Therm-A-Plate intumescent letterbox liner offers a simple and cost effective solution to the problem by providing a lining kit for the cut aperture for both 30 and 60 minute constructions. It is a perfect solution for upgrading your current letterbox without having to buy a new intumescent letter plate. This fire proof letter box kit comprises of 2 Therm A-Flex graphite based intumescent strips, with the material being renowned for its longevity and resistance to degradation by atmospheric influences.

The intumescent liner sections are backed with a self-adhesive tape for easy installation. The faces of the aperture must be clean, dry and dust free for optimum adhesion. Kits may be trimmed to suit the aperture size as required. It is recommended that metal letter plates are used to comply with the recommendations in BS 8214 (1990) and the largest aperture requires a metal tidy but does not have end pieces of intumescent. For the largest 120mm x 300mm apertures the intumescent sections are additionally fixed with 4 no. 30mm x 1.5mm steel pins at 50mm from the aperture ends and 10mm from the door faces.

The performance of the Therm-A-Plate kits has been proven in fire tests carried out to BS 476 Part 22 (1987). Test results (time to failure in minutes) are shown for 45mm and 54mm doors with different aperture sizes, with test reports DFR 9807141, DFR 9804271, DFR 9810292 and DFR 9809151.

Supplied in two sizes, the intumescent letterbox liner is pre-cut to the correct width for 45mm and 54mm thick door leaves, typically 45mm for FD30 fire doors and 54mm for FD60 fire doors. Available in 300mm x 120mm size to suit both FD30 & FD60 applications.

Brand: ISL

Use Case: Fire

Applications: Doors

Test Certification: Fire Tested to BS 476 Part 2 (1987)

Fire Rating: 30 Minutes, 60 Minutes

Material: Graphite Intumescent

Finish: Black

Fixing: Self Adhesive for Surface Mount

Included: 3x Therm-A-Flex Graphite / Therm-A-Plate Intumescent Letterbox Liner

Length mm: 300mm

Width mm: 120mm

Height mm: 45mm, 54mm

Date Added
ISL Therm-A-Plate Technical Data Sheet
18 October 2022
Technical Data Sheet
ISL Therm-A-Plate Fire Test Report
18 October 2022
Test Evidence

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ISL Therm-A-Plate | Intumescent Letterbox Liner
ISL Therm-A-Plate | Intumescent Letterbox Liner
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