Mo. Rev. Stat. § 191.771: Person in control of public places or public meetings, duties.

The person having custody or control of a public place or public meeting shall:

(1) Make reasonable efforts to prevent smoking in the public place or public meeting by posting appropriate signs indicating no-smoking or smoking area and arrange seating accordingly. These signs shall be placed at a height and location easily seen by a person entering the public place or public meeting and not obscured in any way;

(2) Arrange seating and utilize available ventilation systems and physical barriers to isolate designated smoking areas;

(3) Make a reasonable request of persons smoking to move to a designated smoking area;

(4) Allow smoking in designated areas of theater lobbies only.