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Selected Application Recommendations Fumes, Vapors, Hood & Duct Service Composites are widely used in hood, ducting, and ventilation systems due to corrosion resistance, cost, weight considerations, and dampening of noise. Generally speaking, corrosion resistance is quite good, even with relatively aggressive chemicals since there is so much dilution and cooling associated with the high volume of air. When dealing with vapors it is good practice to compute the dew point associated with individual components of the vapor and to assess the chance that the ducting may pass through the relevant dew point to result in condensation and hence high localized concentration of condensate. Because of the high air volume, the dew points are reduced and there is benefit from the low thermal conductivity of the composite which has an insulating effect. If fumes are combustible, applicable fire codes should be checked especially if there is chance that an explosive mixture could be encountered. Accidental fires are always a concern with ducting due to potential accumulation of grease or other combustibles. If a fire indeed occurs, drafts may serve to increase fire propagation. Concern is highest for indoor applications, especially in regard to smoke generation. Brominated flame retardant resins with combined corrosion resistance are normally selected due to their self -extinguishing properties as well as reduced flame spread. Unfortunately, the chemical mechanisms which serve to reduce flame spread can lead to reduced the rate of oxygen consumption, which generates smoke or soot. Many techniques have evolved to contend with smoke generation, including the use of fusible link counterweighed dampers which can shut off air supply. Dominant relevant standards are those of the National Fire Prevention Association (NFPA) and the International Congress of Building Officials (ICBO). DION® FR 9300 flame retardant vinyl ester is widely used in ducting applications and conforms to ICBO acceptance criteria. DION® flame retardant resins will meet the ASTM E-84 Class 1 flame spread requirement of 25 when blended with the appropriate amount of antimony trioxide. Antimony trioxide provides no flame retardance on its own, but has a synergistic flame-retardant effect when used in conjunction with brominated resins. It is typically incorporated into resin at a 1.5-5.0% level. Please consult the product bulletin for a specific resin to obtain its antimony trioxide requirement. Antimony trioxide typically is not included in the corrosion liner for duct systems handling concentrated wet acidic gases in order to maximize corrosion resistance. It is used in the structural over -wrap to provide good overall flame retardance. To maximize flame retardance in less aggressive vapor -phase environments, antimony trioxide may be included in the liner resin.