Duct Penetrations

[BayPointArchitect]

After studying Chapter 7 of the building code a few times, I have come to the general conclusion that the intent is to provide fire dampers within fire-rated barriers in such a way that air supply ducts are not circulating contaminated air between fire areas or segregated compartments. In other words, if tenant #1 has smoke and that smoke gets into the ductwork which serves no other tenant - then who really cares except for tenant #1?

Attached is a sketch that illustrates the quandary presented by my mechanical inspector and my building inspector.

A 26 guage duct connects the roof top unit without any openings into second floor. The supply and return air ducts serve a first floor tenant only.

Thank you for your insight.

ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner

 

[cda]

Nope

Not the case all the time

I am working on a hotel that has duct connected room to room, penetrating rated walls.

Building is sprinkled and that is supposed to save everyone.


Does not seem right, but is legal

In my mind fire in one room spreads smoke and heat to another.

 

[steveray]

This might get you there, but you may also want to look at shafts and fire partitions....AND NO FLEX DUCT!


717.5.2 Fire barriers. Ducts and air transfer openings of fire
barriers shall be protected with approved fire dampers
installed in accordance with their listing. Ducts and air transfer
openings shall not penetrate enclosures for stairways,
ramps and exit passageways except as permitted by Sections
1022.4 and 1023.6, respectively.
Exception: Fire dampers are not required at penetrations
of fire barriers where any of the following apply:

3. Such walls are penetrated by ducted HVAC systems,
have a required fire-resistance rating of 1 hour or
less, are in areas of other than Group H and are in
buildings equipped throughout with an automatic
sprinkler system in accordance with Section
903.3.1.1 or 903.3.1.2. For the purposes of this
exception, a ducted HVAC system shall be a duct
system for conveying supply, return or exhaust air as
part of the structure's HVAC system. Such a duct
system shall be constructed of sheet steel not less
than No. 26 gage thickness and shall be continuous
from the air-handling appliance or equipment to the
air outlet and inlet terminals.

 

[steveray]

717.5.4 Fire partitions. Ducts and air transfer openings that
penetrate fire partitions shall be protected with listed fire
dampers installed in accordance with their listing.
Exceptions: In occupancies other than Group H, fire
dampers are not required where any of the following
apply:

4. Such walls are penetrated by ducted HVAC systems,
have a required fire-resistance rating of 1 hour or
less, and are in buildings equipped throughout with
an automatic sprinkler system in accordance with
Section 903.3.1.1 or 903.3.1.2. For the purposes of
this exception, a ducted HVAC system shall be a
duct system for conveying supply, return or exhaust
air as part of the structure’s HVAC system. Such a
duct system shall be constructed of sheet steel not
less than No. 26 gage thickness and shall be continuous

 

[rgrace]

717.6.1 (2015 IBC) permits this installation without requiring the shaft. I suppose if one chooses to install a shaft when not required, we have to look at it as such. If it looks like a duck and sounds like a duck, it must be a duck? At this point "C" would apply based on 717.5.3, assuming that there are no unknown factors that would prohibit a duct penetration in this shaft (floor would be considered as the bottom of the shaft). If this shaft were identified as a chase rather than a shaft, 717.6.1 could apply and then "B" would be applicable, fire damper at the floor line because the duct doesn't connect more than two stories (openings in the duct on the second story have no relevance, the duct is connecting the two stories, if openings were relevant, language such as found in 717.5.4.1 exception 2 would be present). But wait, 717.6.1 allows for an "OR", "duct is protected in accordance with Section 714.4". This means that "D" could be applicable if "D" were reworded accurately to include the language "through-penetration firestop system" instead of annular space fire caulked, aaaaannd one were able to produce such a tested system applicable to these conditions (floor/ceiling assembly, duct gage and size, etc). Finally, if the penetrations into the top of the shaft were capable of being moved to the roof line rather than through the second floor shaft wall, option "E) No protection required at all" could be created per 713.11 exception 3.

 

[Builder Bob]

The shaft wall must be continuous and enclosed at the bottom as a fire barrier - since shaft walls are fire barriers (pink walls) the orange fire rated floor ceiling assembly is also a fire barrier by default.

Fire partitions are not in this conversation - it is all related to duct penetrations of fire barriers.

 

[ADAguy]

Imagine trying to explain/justify this in court following a fire?

 

[Builder Bob]

yup - fun fun fun

 

[HVAC]

Are fire dampers required when a duct is passing through the roof, considering I already have motorized smoke fire dampers on the roof?

Similarly, in the basement, I have motorized smoke fire dampers, so are fire dampers required when the duct in the basement is passing through the ground floor slab?