Details test and examination criteria for Category I, Category II, Category III and Category IV low-pressure steam and hot water boilers for use with natural, manufactured and mixed gases, liquefied petroleum gases and LP gas-air mixtures. A boiler is defined in the standard as a boiler operating at or below the following pressures or temperatures: steam heating boiler - 15 psi (103.42 kPa) steam pressure; hot water heating or supply boiler - 160 psi (1.10 MPa) water pressure, 250F (121C) water temperature.