Materials for vents, or vent connectors on domestic or small commercial installations, shall be such as to resist the corrosive action of flue gases and condensate. In general, this requirement prohibits the use of black iron, galvanized iron, or copper for vents or vent connectors for gas designed appliances. Iron only shall be used at higher flue temperatures or on large commercial or industrial burner installations where the products of combustion are, at all times, at a temperature greater than the dew point.
Galvanized steel vent or aluminized steel (factory vent kits) may be used for venting sealed combustion appliances.
Plastic vent pipe may be used in accordance with the terms of the listing and the appliance manufacturer’s installation instructions.