Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 149, § 18C

Power transmission equipment (such as gears, belts, pulleys, sprockets, etc.) shall be enclosed or guarded in a manner that will prevent accidental injury to workers.

Prime movers, machinery and equipment shall not be cleaned, adjusted or repaired while in motion. When, due to the process, it is not possible to shut down the machinery, extension swabs, brushes, scrapers or other extended tools shall be used to minimize employee hazards. Where the machine is equipped with lockable controls, the control shall be locked in the “off” position. Caution signs shall be placed on the controls of the machines during repair work.