I am working on a 3 story building. 3rd story is a attic with metal deck as its floor. But it is accessible and has general storage. I have a mechanical duct which penetrates the attic-metal deck floor and the 2nd floor. As per NFPA90A section 5.3.2, if I penetrate one floor, I can provide fire ducts instead of a shaft enclosure. Now, if I consider metal deck (attic floor) penetration as floor penetration, then that duct is penetrating 2 floors, so I need to provide a rated shaft. But if I am not considering the metal deck penetration as floor penetration, I can just install fire dampers and avoid provision of shaft enclosure.
So my concern is basically, do I consider metal deck penetration as a floor penetration?
See the schematic attached.