Missouri Revised Statutes Title XVIII. Labor and Industrial Relations § 293.380. Coal mine operated, how--abandoned workrooms sealed, penalty

1. The owner, agent or operator of any coal mine in this state, employing five or more persons, if said mine is worked on the room and pillar plan, shall cause the work in such mine to be prosecuted in the following manner, and none other, to wit: Two entries must be driven parallel for the ingress and egress of the air, and crosscuts must be made at intervals not to exceed fifty feet apart, and no rooms, entries or other openings shall be allowed to start inside of the last crosscut until the next one be made; and further, that it shall be unlawful for any owner, operator or agent for any person, persons, corporation or company to permit the mouth or mouths of worked-out or abandoned rooms or entries in any coal mine to remain open for a period exceeding one month from the date of abandonment of any such room, rooms, entry or entries.

2. All such abandoned work as designated must be securely sealed in such manner as will effectually prevent the escape of all gases or other impurities calculated to vitiate the ventilative current of a mine; provided, that the sealing of rooms and entries herein provided for shall only be required in such mines and places therein as the director of the division of mine inspection shall in his discretion deem necessary for insuring the health and safety of workmen therein.

3. Any owner, agent or operator in charge of any coal mine worked on the room and pillar plan failing to comply with the provisions of this section shall be deemed guilty of a misdemeanor, and upon conviction shall be punished by a fine of not less than one hundred dollars nor more than one thousand dollars, or by imprisonment in the county jail not less than six months nor more than one year, or by both such fine and imprisonment and every day that the mine is operated contrary to the provisions of this section, after the owner, agent or operator in charge thereof shall have been convicted for a first offense under this section, shall be and constitute a separate and distinct subsequent offense, and shall be punished as such.