Composite duct structure determines it must have excellent fire performance, structural characteristics of composite duct is in the middle of the foam board wrapped non-combustible materials, avoid direct contact with fire, but also to ensure one of the conditions of retardant foam board.

B1 grade ceramic fiber insulation materials, rock wool, glass wool, perlite, vermiculite, diatomite insulation bricks, rubber insulation materials. There is more insulation material strength is poor, high density, thermal conductivity higher issues. Ceramic wool, rock wool fibers loose, easy to layer, strength poor, high density, suitable for high temperature boiler pipe insulation, not suitable for duct insulation.

Urea-formaldehyde resin with glass fiber, the higher the strength of the adhesive, the greater the amount added urea-formaldehyde resin, and urea-formaldehyde resin increases result in dosage and toxicity of glass fiber thermal value generated by the combustion increases, thus achieving duct strength requirements Glass fiber is flame retardant B1 level only.

Glass wool board is commonly used metal duct insulation materials, insulation because of its easily damaged, prone to cold (hot) bridge, resulting in energy loss. Meanwhile fiberglass will pollute the environment.

Expanded perlite and vermiculite are non-combustible insulation materials, water glass adhesive bonding can be made by a small-sized flat, semi-circular shape, for boiler heat pipe insulation, roof insulation. Because of its density, thermal conductivity, high strength and poor, not suitable for duct.

Calcined diatomaceous earth became lightweight insulation bricks, refractory temperature of 1000 ℃, can be used for furnace insulation, but not suitable for duct insulation.

Rubber insulation material is flame retardant materials, light, fire resistance class calorific value, toxicity are composite duct requirements applicable to duct insulation.

The above materials, composite duct now mainly rubber insulation materials. Central British cable Roxy products are sampled by the provincial fire department to the producer, and sample letters served on the National Fire Protection Building Materials Quality Supervision and Inspection Center to test and determination, a survey report, by virtue of the production units must report their inspection determining the level of product identification, after identification by the provincial public security department issued a production license, organization of production.