If a mechanical ventilating exhaust system is required in any room, air may be exhausted to corridors or uninhabited rooms through direct openings or horizontal ducts not to exceed 5 feet (1525 mm) in length if all of the following requirements are met:
1. The room being supplied does not contain dangerous or noxious fumes, odor or dust; and
2. Adequate relief openings for mechanical exhaust exist in such corridors or uninhabited rooms.