Preface This publication represents a basic standard for safe operation, substantial and durable construction, and acceptable performance of gas-fired low pressure steam and hot water boilers. It is the result of years of experience in the manufacture, testing, installation, maintenance, inspection and research on gas-fired low pressure steam and hot water boilers designed for utilization of gas. There are risks of injury to persons inherent in appliances that, if completely eliminated, would defeat the utility of the appliance. The provisions in this standard are intended to help reduce such risks while retaining the normal operation of the appliance. Scope 1.1.1 This standard applies to newly produced gas-fired low-pressure steam and hot water boilers with gas inlet pressure ratings not exceeding 1/2 psi (3.5 kPa) and having input ratings of less than 12,500,000 Btu/hr (3 663 389 W) (see Part IV, Definitions), hereinafter referred to as boilers*, constructed entirely of new unused parts and materials, for operation at or below the following pressures and temperatures: Steam heating boilers 15 psi (103.42 kPa) steam pressure Hot water heating boilers 160 psi (1.10 MPa) water pressure 250°F (121°C) water temperature Hot water supply boilers 160 psi (1.10 MPa) water pressure 250°F (121°C) water temperature a. For use with natural gas; b. For use with manufactured gas; c. For use with mixed gas; d. For use with liquefied petroleum gases; and e. For use with LP gas-air mixtures. The construction of boilers for use with the above-mentioned gases is covered under Part I. The performance of boilers for use with the above-mentioned gases is covered under Part II.