Modifies provisions relating to indoor air quality

HB 1901 replaces Missouri's outdated indoor air quality laws with a new "Missouri Clean Indoor Air Act" (sections 191.2710-191.2750). The bill prohibits smoking and vaping in most enclosed public areas - including bars, restaurants, and workplaces - while defining specific terms like "bar," "cigar-tobacco bar," and "electronic smoking device" (ESD) to clarify enforcement. It directly affects businesses (employers), employees, and public venues by requiring smoke-free environments, with strict rules for cigar-tobacco bars (e.g., freestanding locations and revenue limits). The law includes penalty provisions for violations and explicitly exempts entryways and certain medical devices.