N.Y. Labor Law § 204
6. Definitions. a. For purposes of this section, the term "boiler" shall mean a closed vessel in which water is heated, steam is generated, steam is superheated, or any combination thereof, under pressure or vacuum for use externally to itself by the application of heat from combustible fuels, electricity, or any other source, but shall not include a device or apparatus used solely to heat water for a hot water supply system. The term "boiler" shall include the apparatus used by which heat is generated, and all controls and devices related to such apparatus or to the closed vessel. The term "boiler" also shall include fired units for heating or vaporizing liquids other than water where these units are separate from processing systems and are complete within themselves. b. The term "miniature boiler" shall mean a nonelectric fired pressure vessel which does not exceed inside shell diameter of sixteen inches, forty-two inches over-all length of outside to outside of heads at center, water heating surface of twenty square feet, and maximum allowable working pressure of one hundred pounds per square inch. c. For the purposes of this section, the term "unfired pressure vessel" shall include containers for the containment of internal or external pressure which may be obtained from an external source or by the application of heat from a direct or indirect source, or any combination thereof, provided however, that the term "unfired pressure vessel" shall not include: