As used in the Boiler Inspection Act, unless the context otherwise requires:

(1) Authorized inspection agency means an authorized inspection agency as defined in NB-369, National Board Qualifications and Duties for Authorized Inspection Agencies (AIAs) Performing Inservice Inspection Activities and Qualifications for Inspectors of Boilers and Pressure Vessels;

(2) Board means the Boiler Safety Code Advisory Board; and

(3) Boiler means a closed vessel in which water or other liquid is heated, steam or vapor is generated, steam or vapor is superheated, or any combination thereof, under pressure, for internal or external use to itself, by the direct application of heat and an unfired pressure vessel in which the pressure is obtained from an external source or by the application of heat from a direct source. Boiler includes a fired unit for heating or vaporizing liquids other than water only when such unit is separate from processing systems and complete within itself.