rgrace
Sawhorse
First and foremost, this is a membrane penetration by a duct of a one hour fire-resistance-rated floor/ceiling assembly (this is not a vent; see IMC Chapter 2 for vent definition). This penetration is covered by IMC Section 607 Duct and Transfer Openings. 607.6 refers to duct and transfer openings in horizontal assemblies. This is not a through penetration, so 607.6.1 is not applicable. 607.6.2 refers to membrane penetrations. This is what we have. This section provides two choices; 1- shaft, 2- ceiling radiation damper. So, the real question is, can I install a ceiling radiation damper in the duct that exhausts my residential hood? 
BTW, the suggestion for installing the duct within the wall cavity and penetrating the top plate is an exception to 607.6.1, which I have already established that this is not a through penetration. Does this proposed alternative meet the spirit and functional intent of the code? Perhaps, if all of the items contained in the exception were met
BTW, the suggestion for installing the duct within the wall cavity and penetrating the top plate is an exception to 607.6.1, which I have already established that this is not a through penetration. Does this proposed alternative meet the spirit and functional intent of the code? Perhaps, if all of the items contained in the exception were met