ASHRAE Journal - July 2014 - 42

Column EnginEEr's notEbook
Stephen W. Duda

Fire & Smoke Damper
Application Requirements
By Stephen W. DuDa, p.e., Beap, hBDp, hFDp, FelloW aShRae

Anecdotally, I am aware that some HVAC engineers and designers are uncertain of
the requirements for fire dampers and smoke dampers, especially with regard to
the difference between partition types. Some play it safe and specify fire and smoke
dampers where they really are not required. Some may even find they have been overspecifying protective dampers throughout their career. So I have compiled this Fire
and Smoke Damper Summary for HVAC engineers and designers based on the 2012
International Building Code1 (the 2009 edition has the same requirements but with
different paragraph numbering). Most states and local jurisdictions in North America
use the International Building Code, either outright or as a state adaptation. Where
the IBC is not enforced, NFPA 90A2 can be used for guidance.
Fire-Rated Construction
There are four types of fire-resistance rated walls.
Before you can know what type (if any) fire damper to
use, you first must know which of the four types of walls
you have.
Fire Walls (IBC Section 706) are major separation
walls between buildings or are used to divide one
building into separate buildings. A fire wall actually
allows you to treat the spaces on opposite sides of the
wall as totally separate buildings. These are usually
three- to four-hour rated, and are usually structurally
independent. You cannot run a duct or air transfer
opening through a fire wall located on a property or
lot line-not at all-not even with a fire damper. If
you run a duct or air transfer opening through a fire
wall located within a building, use a three-hour fire
damper. This is the most restrictive of the various
types of fire-rated walls, and is rather rare on most
building projects. Most fire-rated walls within buildings are not this extreme.
Fire Barriers (IBC Section 707) are the medium-rating
level of the various types of fire-rated walls. Examples
aNFPA 90A is slightly more forgiving here. It allows omission of a fire damper at ducted penetrations
of fire barriers and partitions rated less than two hours, even if the building is not fully sprinklered
(¶5.3.1.1).

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include exit passageway enclosures, atrium boundaries,
stairwell enclosures, and separations between occupancies in a mixed-use building. These are usually twohour rated, but there are exceptions, so check with the
architect.
You cannot run a duct or air transfer opening
through an exit passageway enclosure or stairwell
enclosure (not at all; not even with a fire damper)
unless that duct is for the purpose of independent
stairwell pressurization. If you run a duct through
other types of fire barriers, use a 1.5 hour fire damper.
But there is an exception: If the fire barrier is only onehour rated, and if the building is fully sprinklered,a
and if the system is fully ducted (not an air transfer
opening), then you don't need a fire damper (IBC
¶717.5.2, Exception #3).
Shaft Enclosures (Section 713) are a special type of fire
barrier used to enclose shafts. These are usually twohour rated. Shaft enclosures are not required if all of the
following are true: (a) fully sprinklered building; (b) not
a hospital or prison; (c) connects only two floors and no
more. In this case, use a 1.5 hour horizontal fire damper
at the floor line. Other than the previous item, shaft
Stephen W. Duda, p.e., is a senior mechanical engineer at Ross & Baruzzini, Inc. in St. louis.

ASHRAE Journal - July 2014

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