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Section 608 Air Outlets and Air Inlets

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608.1 Air Outlets
Air outlets shall comply with Sections 608.1.1 through 608.1.3.
608.1.1 General
Air supplied to any space shall not contain flammable vapors, flyings, or dust in quantities and concentrations that would introduce a hazardous condition.
608.1.2 Construction of Air Outlets
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.
608.1.3 Location of Air Outlets
The location of air outlets shall comply with the following requirements:
  1. Air outlets shall be located at least 3 inches (76.2 mm) above the floor.

    Exception: Air outlets may be located less than 3 inches (76.2 mm) above the floor where provisions have been made to prevent dirt and dust accumulations from entering the system.
  2. Where located less than 7 feet (2133.6 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.
  3. 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:
    1. Grilles up to 3 square feet (0.2787 m2) in gross area shall be designed to support a concentrated live load of 250 pounds (113.4 kg) on any 4 square inches (2580.6 mm2) of surface.
    2. 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.
    3. If located where they may be walked upon, the opening in grilles shall reject a 1/2-inch (12.7 mm) sphere.
608.2 Air Inlets (Return or Exhaust or Return and Exhaust)
Air inlets shall be constructed in accordance with Sections 608.2.1 through 608.2.3.
608.2.1 General
Air shall not be recirculated from any space in which flammable vapors, flyings, or dust is present in quantities and concentrations that would introduce a hazardous condition into the return air system.
608.2.2 Construction of Air Inlets
Air inlets shall be constructed of noncombustible material or a material that has a maximum flame spread index/rating of 25 and a maximum smoke-developed index/rating of 50.
608.2.3 Location of Air Inlets
The location of air inlets shall comply with the following requirements.
  1. Air inlets shall be located at least 3 inches (76.2 mm) above the floor.

    Exception: Air inlets may be located less than 3 inches (76.2 mm) above the floor where provisions have been made to prevent dirt and dust accumulations from entering the system.
  2. Where located less than 7 feet (2133.6 mm) above the floor, inlet openings shall be protected by a grille or screens having openings through which a 1/2-inch (12.7 mm) sphere cannot pass.
  3. 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:
    1. Grilles up to 3 square feet (0.2787 m2) in gross area shall be designed to support a concentrated live load of 250 pounds (113.4 kg) on any 4 square inches (2580.6 mm2) of surface.
    2. 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.
    3. If located where they may be walked upon, the opening in grilles shall reject a 1/2-inch (12.7 mm) sphere.

Related Code Sections

608.1.3 Duct Systems, Location of Air Outlets
The location of air outlets shall comply with the following requirements: Air outlets shall be located at least 3 inches (76 mm) above ...
608.1.1 Duct Systems, General
Air supplied to any space shall not contain flammable vapors, flyings, or dust in quantities and concentrations that would introduce a hazardous ...