Motion picture booth safety regulations are designed to mitigate the extreme fire hazards associated with nitrocellulose films. According to the 1935-miami-dade-building-code, every motion picture machine using inflammable films must be enclosed in a booth constructed with not less than one-hour fire-resistive-construction-requirements (p. 275). The booth must have a floor area of at least 50 square feet per machine and a height of at least 7 feet (p. 275). The floor must be masonry, reinforced concrete, or covered with at least 2 inches of masonry (p. 275).
Entrances to the booth must be equipped with tight-fitting, self-closing fire doors that open outwardly and lack latches (p. 275). Openings for projection and observation are strictly limited in size and number; for instance, each projection port must not exceed 120 square inches, and observation ports must not exceed 150 square inches (p. 275). These ports must be covered with plate glass and protected by shutters made of sheet metal, which are held open by fusible links rated at 160°F (p. 276). These shutters must close automatically within 5 seconds upon the failure of the fusible link (p. 276).
Ventilation is critical; booths must have air inlets near the floor and exhaust vents at the top for each machine, connected to a masonry flue or going through the roof (p. 276). An exhaust fan must provide a complete air change every 10 minutes (p. 276). All fixtures within the booth must be metal or incombustible, and machines must be securely fastened to the floor (p. 276). Films not in use must be stored in metal cabinets with self-closing doors, with each compartment holding no more than 10 reels (p. 276).
These regulations align with broader motion-picture-booth-safety standards and reference guidelines from the national-board-of-fire-underwriters and the national-fire-protection-association (p. 276). Safety film (cellulose acetate base) is exempt from these strict requirements (p. 276).