A room of light hazard occupancy classification having unobstructed construction and floor areas not exceeding 800 ft2 (74. 3 m2) that are enclosed by walls and a ceiling. Openings in walls not exceeding 8 ft (2. 44 m) in width to adjoining spaces are permitted if the minimum lintel depth is 8 in. (203 mm) from the ceiling. A single opening of 36 in. (914 mm) or less in width without a lintel is permitted when there are no other openings to adjoining spaces.