In each case, openings into fire-resistance-rated construction shall be limited to those needed for maintenance and operation and shall be protected by self-closing fire-resistance-rated devices in accordance with the International Building Code for enclosure wall opening protectives. Exit enclosure ventilation systems shall be independent of other building ventilation systems.
The use of gypsum boards to form plenums shall be limited to systems where the air temperatures do not exceed 125°F (52°C) and the building and mechanical system design conditions are such that the gypsum board surface temperature will be maintained above the airstream dew-point temperature. Air plenums formed by gypsum boards shall not be incorporated in air-handling systems utilizing evaporative coolers.
|DUCT SIZE||GALVANIZED||ALUMINUM |
MINIMUM THICKNESS (in.)
|Minimum thickness (in.)||Equivalent galvanized gage no.|
|Round ducts and enclosed rectangular ducts |
14 inches or less
16 and 18 inches
20 inches and over
|Exposed rectangular ducts |
14 inches or less
Over 14 inchesa
Exception: Where a duct connection is made that is partially inaccessible, three screws or rivets shall be equally spaced on the exposed portion so as to prevent a hinge effect.
Exception: Smoke detectors are not required in the return air system where all portions of the building served by the air distribution system are protected by area smoke detectors connected to a fire alarm system in accordance with the International Fire Code. The area smoke detection system shall comply with Section 606.4.
Exception: Individual smoke detectors shall not be required for each fan-powered terminal unit, provided that such units do not have an individual design capacity greater than 2,000 cfm (0.9 m3/s) and will be shut down by activation of one of the following:
- The supervisory signal at a constantly attended location is not required where the duct smoke detector activates the building’s alarm-indicating appliances.
- In occupancies not required to be equipped with a fire alarm system, actuation of a smoke detector shall activate a visible and audible signal in an approved location. Duct smoke detector trouble conditions shall activate a visible or audible signal in an approved location and shall be identified as air duct detector trouble.
|TYPE OF PENETRATION||MINIMUM |
|Less than 3-hour fire-resistance-rated assemblies||11/2|
|3-hour or greater fire-resistance-rated assemblies||3|
Exception: Fire dampers are not required at penetrations of fire barriers where any of the following apply: