Mass. Gen. Laws ch. 146, § 13: Persons authorized to inspect boilers

Section 13. The inspection of boilers and appurtenances shall be made by the division, under the supervision of the chief, or by inspectors of insurance companies authorized to insure steam boilers in the commonwealth; or, in the case of shop inspections in a boiler shop outside of the commonwealth, by such other inspectors holding a national board of boiler and pressure vessel inspectors commission as are approved by the chief of inspections.