Mo. Rev. Stat. § 292.050
The openings of all hatchways, elevators and wellholes upon every floor of every manufacturing, mechanical or mercantile or public building in this state shall be protected by good and sufficient trapdoors or self-closing hatches or safety catches, or strong guard rails at least three feet high, and all due diligence shall be used to keep such trapdoors closed at all times, except when in actual use by the occupant of the building having the use and control of the same. Whenever the director of the inspection section, or one of his assistants or deputies, finds any violations of the foregoing requirement to guard hatchways, elevators and wellholes, he shall at once, in writing, notify the owner or owners thereof, or the person or persons in charge of said appliance or appliances, to make the necessary alterations, additions or repairs within ten days; and if said alterations, additions or repairs are not made within ten days from the date of such notice, the director or his assistant or deputy, shall seal such appliance or appliances in such a manner as to render the same inoperative until there has been compliance with the order of the director.
§ 292.050, RSMo