IMN/IMP is a two-part combined intumescent fire and smoke seal, specifically designed for the meeting stiles of FD30S fire and smoke-resisting door assemblies.

At the meeting stiles the seal consists of two opposing extruded aluminium alloy profiles - IMN and IMP - each with twin reservoirs which contain substantial reserves of Sealmaster intumescent material. IMN also holds a self-extinguishing elastomeric blade, which rest against IMP when the doors are closed. At the head and hanging stiles IMN is used on its own with the smoke seal making contact with the door or frame.

In new doorsets, both profiles are rebated into the centre of opposing door edges at meeting stiles. Where IMN/IMP is fitted to an existing door assembly, the stiles of the door are easily rebated. The seal is interrupted at the hinges and lock/latch striker plate positions, and protection at these points is normally not essential for FD30S doors (see BS 8214).

In normal use, the elastomeric blade seals the gap between the doors, and acts as an efficient draught seal.

As the fire develops, the elastomeric blade provides a barrier to the passage of smoke and hot gases. Once the fire reaches the IMN/IMP seal, the intumescent material foams, swells and fills the gaps between the doors. Since the foam remains soft during the period of intumescent action, it exerts minimal pressure, allowing the doors to remain in their original positions.

An IMN/IMP combination seal with elastomeric blade insert, has been tested on a double leaf, timber door assembly by TRADA. A fire resistance in excess of the 60 minutes was achieved. Copies of test results are available on request.

IMN/IMP fire and smoke seals have been tested and approved by Certifire to conform to BS476 part 22. This is the most demanding 3rd party certification scheme in the industry.