Intumescent Seals is a division of Dixon International Group Limited


Ironmongery such as locks latches and hinges are essential components of many fire door sets with ratings over FD30. Whilst essential for the operation of the fire door set such ironmongery introduces weaknesses to the door’s overall performance unless some additional protection is applied over and above that afforded by the normal intumescent door edge seals. The performance weakness is due to premature burn through at ironmongery positions and at the upper and mid height hinge positions in particular. This has been recognised officially in BS8214:2008. Intumescent Seals offer tailored solutions to the problem using THERM-A-FLEX and THERM-A-STRIP intumescent materials.


THERM-A-FLEX is a black, flexible graphite based intumescent material giving an approximate 20 fold in crease in volume when exposed to heat. Its activation temperature is around 180°C. THERM-A-STRIP is a white, flexible phosphate based intumescent product giving an approximate ten fold increase in volume when exposed to heat. Its activation temperature is around 150°C.


THERM-A-FLEX or THERM-A-STRIP are used to protect fire door ironmongery by fitting them underneath hinge blades, around lock cases and under or around closer mechanisms. THERM-A-FLEX is used where significant intumescent expansion pressure is required and THERM-A-STRIP where a lower level of intumescent expansion pressure is required.



THERM-A-FLEX and THERM-A-STRIP make a critical contribution to the fire resistance of fire door sets of FD60 specification and above.


THERM-A-FLEX and THERM-A-STRIP materials can be supplied cut to suit particular ironmongery designs in 1mm or 2mm thickness and with or without self adhesive tape applied. Intumescent Seals is able to supply ironmonger protection to suit many standard ironmongery items. Non-standard items are also available to special order.

Test Evidence

The fire performance of THERM-A-FLEX and THERM-A-STRIP based ironmongery protection has been proven in fire tests of several fire door set configurations to BS476-22:1987.

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