Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 146, § 8

No person shall operate or cause to be operated any boiler required by this chapter to be inspected until it has been inspected, and the certificate of inspection required by section twenty-three or twenty-five has been issued and so placed in the engine or boiler room of the plant as to be easily read, or in the case of a portable boiler kept with it and always accessible.