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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. Is it necessary to upgrade from flame-retardant B1 grade to non-combustible A grade? However, there is currently no A-grade fireproof insulation material that is suitable for central air conditioning ducts. In this article, the author analyzes the issue from several perspectives.
Flame-retardant B1 insulation boards are not easily ignited. At present, the commonly used insulation materials in central air conditioning ducts include:
1. Glass-magnesium composite board ducts, made with flame-retardant B1 polystyrene foam board as the core, and glass fiber-reinforced magnesium oxychloride cement composite on both sides.
2. Polyurethane aluminum foil composite ducts, using flame-retardant B1 polyurethane foam board as the insulation layer, with aluminum foil laminated on both sides.
3. Phenolic aluminum foil composite ducts, made with flame-retardant B1 phenolic foam board as the core, combined with aluminum foil on both sides.
4. Color steel plate insulated composite ducts, which use flame-retardant B1 polystyrene, polyurethane, or phenolic foam boards as the insulation core, with color steel plates laminated on both sides.
Through analysis of test data, the following findings were obtained:
1. The properties of organic foam ventilation ducts cannot meet Class A requirements.
2. Although glass wool composite ducts use inorganic foam as the main material, to meet the structural strength requirements, more adhesive is added, increasing the amount of organic binder. This affects the heat value and toxicity of the glass wool, causing the samples in this test to fail to meet Class A standards.
3. The overall fire performance of the glass-magnesium composite panel duct is excellent, fully meeting the A-level requirements. Although the composite duct also uses polystyrene foam as the insulating core, the foam 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 fully complies with the requirements for Grade A (composite sandwich) materials 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, except for the glass-magnesium composite panel duct, which is classified as non-combustible A grade, all other composite ducts—polyurethane, phenolic, and polystyrene—are only flame-retardant B1 level. The B1 foam boards contain halogen-based flame retardants. From the combustion index and burning behavior, these foam boards will ignite when exposed to fire but will self-extinguish once removed from the fire source. They do not contribute to the spread of fire, thus providing effective fire protection.
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