FD vs FSD

[wordtokyle]

I've been taught to use a rule of thumb of calling for fire dampers in ductwork penetrating walls with a 1-hr fire rating; and calling for combination fire-smoke dampers in ductwork penetrating walls with a 2-hr fire rating.

The problem is that I have no idea where this rule of thumb came from. Has anyone else encountered this? Or better yet, know where this comes from?

 

[cdxx139]

It comes from code.

Here, International Mechancial Code IMC 2009 Section 607 rules. NFPA 90A-19 Figure A.5.3 is a nice pictoral, but doesnt include all updated building code requirements.



knowledge is power

 

[wordtokyle]

Thanks for the response cdxx139. Reading through those codes are actually what brought me here to ask the question.

There is no code or standard where it is simply laid out saying a 1hr wall requires FD and a 2hr wall requires FSD. Am I wrong in believing that the rule of thumb is flawed? And yet, it seems to be very popular.

 

[cdxx139]

Ive never heard of your rule of thumb, but like all rules of thumbs, it will get you by 80% of the time, but when it comes to life safety, do the research. Its an expensive add once everything is built.

As for the other 20%...in some cases, if it is a one hour partition, but the duct is just running through the space and does not have an opening to the space, then you dont need a fire damper.

Now you need a combination smoke fire damper any time you come out of a shaft. There ia an exception that allows a stainless steel subduct to exempt the fire damper, and if the unit runs 24/7, then you can exempt the smoke damper.

Codes are not written to be quick rules of thumbs, because then how would they fill in the 6" binders they come in? They are written to be difficult to read, so the Authority Having Jurisdiction can interpret it how he sees fit on that day. (I've been burnt in the past)

knowledge is power

 

[mauricestoker]

Requirement is application specific, so one size fits all does not work well. For wet labs under NFPA 45, no dampers are to be installed (subducting required). Size of penetration would also be a consideration. Whether the damper is intended for smoke compartmentalization under NFPA 92A or B would be another consideration.

 

[KiwiMace]

As an example - In LA County the AHJ will only want to see CSFD's. Refer your local AHJ on the matter, they don't bite, and often enjoy having someone ask ahead of time rather than fight them on the completed plans.

 

[cry22]

As the name says (Fire/Smoke damper) goes in a smoke partition that is fire rated.
Also needed in RA at each floor at RA shaft.