scope:

This standard applies to newly produced gas fired-duct furnaces, packaged heaters and unit heaters with input rates up to and including 10,000,000 Btu/h (2 931 kW) and utility heaters with inputs up to and including 400,000 Btu/hr (117.2 kW) constructed entirely of new, unused parts and materials:

a. For use with natural gas with inlet gas pressures up to and including 5.0 psi (34.5 kPa); unit heaters, packaged heaters and duct furnace with burners having inputs rates over 400,000 Btu/hr (117 228 kW) may have higher inlet pressures.

b. For use with liquefied petroleum gases; and

c. Convertible for use with natural gas and liquefied petroleum gases, when provision is made for the conversion from one gas to the other.