1.1 Scope 1.
1.1 This standard applies to newly produced gas-fired duct furnaces and unit heaters of any input constructed entirely of new, unused parts and materials: (a) For use with natural gas; (b) For use with liquefied petroleum gases; (c) Convertible for use with natural gas and liquefied petroleum gases, when provision is made for the conversion from one gas to the other. 1.
1.2 The term ""appliance"" when used h