Air supplied to any space shall not contain flammable vapors, flyings, or dust in quantities and concentrations that would introduce a hazardous condition.
Air outlets shall be constructed of noncombustible material or a material that has a maximum smoke developed index/rating of 50 and a maximum flame spread index/rating of 25.
The location of air outlets shall comply with the following requirements:
- Air outlets shall be located at least 3 inches (76 mm) above the floor.
Exception: Air outlets may be located less than 3 inches (76mm) above the floor where provisions have been made to prevent dirt and dust accumulations from entering the system.
- Where located less than 7 feet (2134 mm) above the floor, outlet openings shall be protected by a grille or screen having openings through which a 1/2-inch (12.7 mm) sphere cannot pass.
- Grilles may be located in floors provided they are installed so that they may be removed for cleaning purposes and provided they are constructed as follows:
- Grilles up to 3 square feet (0.2787 m2) in gross area shall be designed to support a concentrated live load of 250 pounds (114 kg) on any 4 square inches (2580 mm2) of surface.
- Grilles over 3 square feet (0.2787 m2) in gross area shall be designed to support the same loads as the floor in the area where used.
- If located where they may be walked upon, the opening in grilles shall reject a 1/2-inch (12.7 mm) sphere.