The inspection of hot water heating boilers and their appurtenances may be made by inspectors of insurance companies authorized to insure boilers in the commonwealth; or, in the case of shop inspections in a boiler shop outside of the commonwealth, by such other inspectors employed by authorized insurance companies holding a national board of boiler and pressure vessel inspectors commission as are approved by the chief of inspections.
Mass. Gen. Laws ch. 146, § 73