Where the ductwork itself forms a protected shaft, the fire resistance may be achieved by the ductwork material or through the application of a different material applied to sheet steel ducts constructed to the standard under which the product was originally tested and certificated

There are four basic types of fire resistant ductwork that could be required or have special use under fire conditions. The following terms are used in identifying varying performance criteria for such ducts.

1. Ventilation Fire Ductwork: This ductwork is either supply or extract and needs to be fire rated where it passes from a fire compartment through, for example, an escape corridor. It needs to be tested for both type A fire outside and type B fire inside criteria. It is not necessary for the ductwork to maintain its cross sectional area in a fire for it to be acceptable

2. Smoke Extract Fire Ductwork: This ductwork is for extracting smoke from the building and should be fire rated equal to the compartment walls or floors through which it passes for stability, integrity and insulation. The duct must also be tested to prove that its cross sectional area does not reduce by more than 25% by area, both inside and outside the furnace, and to insure that it will achieve its primary function, of extracting smoke. Stability and integrity ratings only are normally required within the area to be protected, i.e. car parks, if the duct is contained within a dedicated shaft or there is at least 500mm separation between the ductwork and combustible materials.

3. Non Domestic Kitchen Extract Fire Ductwork: This is sometimes called grease ducting and should be tested for both type A fire outside and type B fire inside as a kitchen extract duct. Both tests are required as it is important to prevent flammable grease from either catching fire when it passes through an adjacent area, or if the grease itself is already alight, causing a fire to start within the adjacent area by radiant heat

4. Pressurization Ductwork: Pressurization is a method of restricting the penetration of smoke into certain critical areas of the building by maintaining the air within those areas at pressures higher than those in adjacent areas. This particularly applies to protected stairways, lobbies and corridors as smoke inhibits escape, and to fire fighting shafts serving deep basements because of the difficulty in clearing smoke.

Thermofire (Middle East) Limited is capable of undertaking the complete fire rated duct system including supply & installation of the sprayed duct coating to work with the conventional ductwork contractor and fire protect their ductwork, up to 4 hours of fire resistance