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Is a fire damper required in a return or supply air duct to/from a roof top unit through a roof-ceiling assembly?

Question asked by minhyeong1.kim on Jun 26, 2019
Latest reply on Jul 5, 2019 by john.bosyj

Hi. 

I wonder whether a fire damper is required in a return or supply air duct to/from a roof top unit through roof-ceiling assembly or not. The specifics of the case are as follows:

1. It is single story and ordinary hazard industrial building having area of 12000 sqft. 

2. The building is constructed as per type II (222) of NFPA 5000, which means that the roof-ceiling assemblies have 1-hour fire rating.

3. Several roof top units are located on the roof.

4. Supply air and return air ducts are installed through the roof and to the roof top units.

 

In my understanding, clause 5.3.3 of NFPA 90A (2018 ed.) stipulates that fire dampers are required where air ducts are used in a roof-ceiling assembly having fire resistance rating. However, it seems that fire dampers are not required in this case as per figure A.5.3 of NFPA 90A. 

 

 

  <--- No fire damper is indicated on the duct through roof-ceiling assembly to roof top unit.

 

Please advise.

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