Fire Barriers and Smoke Partitions

Fire Barriers and Smoke Partitions


Used in construction for many purposes, including separating occupancies, isolating hazardous areas, enclosing an exit or creating a shaft, fire barriers have a fire-resistance rating in hours, specified by the code. Depending on the purpose, the fire resistance can be as little as half an hour, or it can be one hour, two hours, and, in some cases even three hours. Any fire barrier must be complete both horizontally and vertically (wall extends from the floor slab through any suspended ceiling and is tight against the floor or roof above.) All penetrations of the fire barrier must be sealed to maintain the barrier’s fire resistance, and all doors must be fire-protection-rated doors of the appropriate rating. Fire-protection-rated dampers are required in ducts that penetrate fire barriers with a fire resistance greater than one hour.

Smoke partitions are designed to limit the movement of smoke and are not as substantial as fire barriers. Smoke partitions generally do not have a fire-resistance rating and may terminate at a ceiling. Walls enclosing a sprinkler-protected hazardous area can constitute smoke partitions. The code says that a typical, lay-in acoustical tile ceiling with ducted HVAC can be considered as limiting the transfer of smoke. The doors do not have to be fire-protection-rated but they must be self-closing. No dampers are required in duct penetrations.

Components and Identification


Fire rated walls are generally constructed of sheet rock (5/8” Type X) or masonry.  Any penetrations through the walls for utilities must be properly sealed with fire caulk or other approved sealant or firestop products.  Ducts passing through these walls will typically have a damper that closes under fire conditions.  Openings in rated walls including doors and window glass must also be rated or protected by specially designed sprinklers.

It is not always easy to identify these barriers and partitions.  In newer buildings there are markings indicating the rating or type of wall.  The red fire caulking also helps with identification.

Fire doors must be self-closing and self-latching.  They may be held open by a magnetic device which releases upon activation of the fire alarm system.  They can be identified by a plate on the hinge side of the door.  This plate should not be painted over.  Fire doors are part of a rated assembly which includes the frame, hinges, closer and latching mechanism.  Any glass in fire doors must be rated.  No part of the door assembly should be interchanged with a different part.

Older buildings may have “legacy” components.  These are original doors and walls that were considered to be protective at the time they were installed even if they have no laboratory testing or rating.  Many solid wood doors are considered to be acceptable fire doors, even without listed hardware.  Plaster and lathe walls constructed before the common use of sheet rock are considered to have a fire rating as long as they are intact.  Any renovation projects should consider upgrading these components.

Whenever penetrations must be made through a wall, floor or ceiling, or doors or door hardware replaced or repaired, consideration must be given to the intended fire rating.  Stairwell doors and walls of stairs three stories or more are almost always rated, as are hazardous areas such as large boiler rooms.  If the rating cannot be determined by labels or existing conditions, contact the Zone Manager or University Fire Marshal for guidance.