Intumescent Seals is a division of Dixon International Group Limited


THERM-A-BLADE combines the outstanding performance of THERM-A-FLEX intumescent with a superb twin blade elastomeric seal for maximum smoke control and improved acoustic properties. It provides an alternative to THERM-A-STOP which has a pile smoke seal without compromising the excellent fire performance of THERM-AF-LEX graphite fire seal.


THERM-A-BLADE has been developed to enhance the smoke performance properties of THERM-A-STOP. The fire performance properties of both products are the same as they both contain the same intumescent, THERM-A-FLEX, the first UK manufactured graphite intumescent. The specially developed elastomeric blades are very thin to give a very low deflection force thereby minimising the opening and closing forces when operating the door.


THERM-A-BLADE intumescent fire and ambient temperature smoke seals image

THERM-A-BLADE intumescent fire and ambient temperature smoke seals are available in PVC holders which are 4 mm nominal (actual 4.3 mm). For most latched single-leaf, single swing 30 minute (FD30S) timber fire resisting door assemblies, a single 10 mm x 4 mm or 15 mm x 4 mm strip down each jamb and across the head will usually meet these requirements.

Most latched single-leaf, single swing 60 minute (FD60S) timber fire resisting door assemblies will satisfy the requirements of BS476 : parts 20 and 22 (1987) test procedures when fitted with a single 20 mm x 4 mm strip across the head and down both jambs. Tests carried out to BS EN 1634-1 often require more specific solutions e.g. twin 15 mm x 4 mm seals to achieve a 60 minute rating.

The intumescent foam produced by THERM-A-BLADE is designed to withstand high temperatures - so it is well suited to applications incorporating timber doors with steel frames where conventional intumescent foam compounds break down.


fitting THERM-A-BLADE image

THERM-A-BLADE is a flexible elastomeric insert which has been developed to give maximum fatigue resistance ensuring a long and satisfactory life when installed into a 3 to 4 mm gap between the door edge and the frame.

Narrower gaps than this will shorten the life of the smoke seal. Larger gaps will not be a problem provided that the seal bridges the gap. The seal is fitted into a PVC holder containing THERM-A-FLEX graphite for outstanding fire performance and immune from degradation by carbon dioxide in the atmosphere.


THERM-A-BLADE colour swatches

THERM-A-BLADE is supplied as standard in brown, white, black, grey, cream, red and a light oak woodgrain finish but other colours are available to order.*

Nominal sizes are available in the following dimensions:

  • 10 mm x 4 mm
  • 15 mm x 4 mm
  • 20 mm x 4 mm
  • 25 mm x 4 mm
  • 30 mm x 4 mm
  • 38 mm x 4 mm

and in standard lengths of 1050 mm or 2100 mm.

Other sizes and lengths are available to special order.

* Colours may vary slightly between examples illustrated in print, online and actual examples - which will depend upon lighting conditions in situ.

Test Evidence

THERM-A-BLADE meets the requirements for fire and smoke performance of BS476 :

Cparts 20, 22 & 31.1 . It has also passed the more exacting standards required by Certifire. It is currently being evaluated to the requirements of BS EN 1634-1.

Copies of test certificates and other evidence are available on request.

THERM-A-BLADE - Certifire and IFSA logos

Related Products

Unlatched doors may require additional intumescent material across the head. Latches, hinges, glazed elements, door closers, kick plates, ventilation grilles and other ironmongery may require additional protection in the event of a fire.

Please contact our Technical Department for further advice.