Is Fire-stopping or closure required ???


Situation shown on attached drawing. Issue is:

Given: 1995 CBC was code; non-rated floor separating two levels of a Type II-N building sprinklered and unlimited; open stairway between two floors is allowed; there are ducts from roof equipment down through 2d floor and distributing air to open ceiling at 1st floor; unenclosed ducts are allowed: for cosmetic purposes and to avoid damage to the duct drops, the duct drops were surrounded by walls of steel studs and drywall.

Question: Section 711.3 appears to require fire-stopping around the duct where it penetrates the 2d floor. Given that open stairs are allowed, with free air flow between two floors, what would be the purpose of the fire-barrier at that annular opening, and is it in fact required? Am I missing something?



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Original Post
I only have a copy of the 1998 CBC (1997 UBC), but it may be similar.

Section 711.3 of the 1998 CBC states that if the opening made through the floor is protected with through-penetration fire stops, to the same degree of fire resistance as the floor construction, then a rated shaft enclosure is not required.

So if the degree of fire resistance of the floor is zero (non rated) then the fire stop would be required to have the same rating, which is actually no rating.

The only other thing that I can see that may trigger this type of requirement is if the opening is considered to be concealed within the building construction assemblies. Then, a rated shaft enclosure is required.

Hope this helps.
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