Covers materials, design, construction, installation, inspection and testing of welded carbon and carbon-manganese steel boilers and cast iron boilers intended for land use. It includes directly fired boilers, waste-heat boilers, electric boilers, boilers of locomotive type design and shell boilers of the horizontal, vertical and fire-tube types. It applies to pressure parts connected to the boiler without intervening valves, but not to superheaters, economizers or pressure piping beyond such valves.