Mass. Gen. Laws ch. 149 § 126
No inside or outside door of any building subject to the supervision of the attorney general which, under the provisions of the state building code, is required as a means of free egress or escape from fire, and no inside or outside door of any industrial establishment in which ten or more persons are employed which is marked "exit" or in any other manner designating the same as a means of egress or escape from fire shall, during business hours, be so locked, bolted or fastened that such door cannot be opened from the inside by the use of the ordinary door knob, or by pressure on the door or on a panic release device, so called. No inside or outside door of any other building, other than a dwelling house, wherein any person is employed, which door shall have been determined by the department of fire services, upon the written request of the attorney general, to be a means of such egress and escape shall, during business hours, be locked, bolted or fastened as aforesaid or obstructed in any manner which would not permit free egress. The owner, lessor or lessee, or any other person in charge, of a building or portion thereof any door of which shall be found locked, bolted or otherwise fastened or obstructed in any manner which would not permit free egress, contrary to any provision of this section shall be punished by a fine of not less than five hundred nor more than three thousand dollars or by imprisonment for not more than one year, or both.
Mass. Gen. Laws ch. 149, § 126