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Are fire dampers required at 1-hr shaft walls?

LeeEng (Civil/Environmental)
21 Oct 06 21:21
I could use a bit of help trying to understand the code requirement for fire dampers at shaft walls.  I was reviewing a building air system design that includes a duct riser that extends from the roof down three floors.  The shaft wall is noted as 1-hour rating (as expected).  I understand in a fully sprinklered building, ducts that penetrate 1-hour walls do not require smoke dampers.  Is the same true for shaft walls?  I looked through NFPA 90A, but I could not seem to get a clear answer (the diagram does not provide any insight).  Perhaps I am overlooking the obvious.  Any assistance you can provide is greatly appreciated.  Thank you.  
DrRTU (Mechanical)
21 Oct 06 22:50
A fire damper would not be required. The dwg. at the back of 90A shows plain metal duct going thru a 1hr. rated wall without a damper. Shafts, floors & walls if 1hr. are the same.
GMcD (Mechanical)
21 Oct 06 23:28
In my area of the world- you MUST have a fire damper at any duct that penetrates a fire rated separation, period.  Welcome to Canada, eh.
stanlsimon (Mechanical)
22 Oct 06 0:01
Don't know what your codes are, type of building occupancy, type of construction, ?

Under the International building Code, a sprinkler system may eliminate many dampers.  However your local Authority having jurisdiction may not agree.  
LeeEng (Civil/Environmental)
22 Oct 06 11:13
Thank you for the responses.  I do see the 1-hr wall on diagram.  My original thought was that it does not need a fire damper, but I was having trouble proving it to myself.  However, I think my confusion stemmed from the same figure and some of the language in 90A.  The figure shows a 3-story shaft that should only be 1-hr rated (but is not specified) with fire dampers.  

I read the following two items in 90A that appear to conflict with each other:
"Approved fire dampers shall be provided where air ducts penetrate...rating of 2 hours or more"

"Fire dampers shall be installed at each direct or ducted opening into or out of enclosures required by 3-3.4.1."  The referenced section includes 1-hr construction.

Thanks again.  I think I better understand it now.

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