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Research on fireproof level of central air conditioning duct insulation material
The enhancement of the fire resistance rating of external wall insulation materials has sparked a debate on the insulation materials used in central air conditioning ducts. A key question arises: should the flame-retardant B1 grade be upgraded to non-combustible Grade A? However, there is currently no A-grade fireproof insulation material that is suitable for use in central air conditioning ducts. In this article, the author will analyze this issue from several perspectives.
The B1 flame-retardant insulation board is designed to resist burning. Currently, the main types of insulation materials used in composite air conditioning ducts are as follows:
1. Glass-magnesium composite plate ducts are made with B1-grade polystyrene foam boards, with glass fiber-reinforced magnesium oxychloride cement laminated on both sides.
2. Polyurethane aluminum foil composite ducts use B1-grade polyurethane foam boards as insulation, with aluminum foil bonded to both sides of the foam board.
3. Phenolic aluminum foil composite ducts are constructed using B1-grade phenolic foam boards, with aluminum foil attached to both sides.
4. Color steel plate insulation composite ducts utilize B1-grade polystyrene, polyurethane, or phenolic foam boards, with color steel plates laminated on both sides.
By analyzing test data, the following conclusions were drawn:
1. The properties of organic foam ventilation ducts cannot meet the requirements of Class A fire resistance.
2. Although glass wool composite ducts use inorganic materials as their main component, they require additional adhesives to meet structural strength demands. This increase in organic binders affects the heat value and toxicity of the glass wool, leading to failure in meeting Class A standards during testing.
3. The overall fire performance of the glass-magnesium composite panel duct is excellent, fully meeting the requirements of Class A. Although the core material is still polystyrene foam, it is not directly exposed to flames. While the heat value of the foam board is 30 MJ/kg, the thermal value of the magnesium cement on both sides is only 1.8 MJ/kg. As a result, the glass-magnesium composite panel duct meets the A-grade (composite sandwich) requirements outlined in GB8624-1997 "Classification of Combustion Performance of Building Materials and Products."
According to the analysis by the Sichuan Fire Research Institute under the Ministry of Public Security, only the glass-magnesium composite panel duct achieves the non-combustible Grade A classification. Other types, such as polyurethane, phenolic, and polystyrene composite ducts, remain at the B1 flame-retardant level. These B1 foam boards contain halogen-based flame retardants. From combustion indices and observed phenomena, the foam boards burn when exposed to fire but self-extinguish once removed from the source, without contributing to fire spread.
In conclusion, while upgrading to Grade A may seem beneficial, the current available materials for central air conditioning ducts do not meet these standards. Therefore, careful consideration must be given to balancing safety, cost, and practicality in material selection.
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