Mo. Rev. Stat. § 292.420
For the purpose of disseminating a general knowledge of the provisions of sections 292.300 to 292.440 and of the dangers to the health of employees in any work or process covered by the provisions of sections 292.300 to 292.440, the employer shall post in a conspicuous place in every room or apartment in which any such work or process is carried on, appropriate notices of the known dangers to the health of any such employees arising from such work or process, and simple instructions as to any known means of avoiding, so far as possible, the injurious consequences thereof, and the director of the inspection section shall have prepared a notice covering the salient features of sections 292.300 to 292.440, and furnish a reasonable number of copies thereof to employers in this state affected by the provisions of sections 292.300 to 292.440, which notice shall be posted by every such employer in a conspicuous place in every room or apartment in such place of employment. The notices required by this section shall be printed on cardboard of suitable character and the type used shall be such as to make them easily legible.
§ 292.420, RSMo