Mo. Rev. Stat. § 292.060: Fire escapes.

All manufacturing, mechanical, mercantile or other establishments in this state, of two or more stories in height, in which twenty or more persons are employed above the first floor thereof, shall be provided with at least one or more outside iron fire escapes. For every twenty persons employed on every floor above the second floor of such establishment, there shall be one rope or portable fire escape, and each story shall be amply supplied with means of extinguishing fire.