Use wall fire barrier exceptions to omit ceiling radiation dampers?

[Mech]

New Construction
R-2 Apartment building
2018 IBC

Each apartment main HVAC duct runs in an unrated horizontal soffit and individual ducts tap off the main and penetrate the ceiling membrane of a rated ceiling / floor assembly or a rated ceiling / roof assembly. Section 717.6.2 requires protection of the ceiling membrane unless one of the exceptions apply (of which none do.) I recently heard that some design professionals utilize IBC 717.5.4, exception 3, to omit ceiling radiation dampers where ductwork penetrates the ceiling membrane. This code section is for Fire Partitions and the exceptions for omitting fire dampers are listed for walls, not ceilings. I was told if I read the code and commentary enough, I can connect code sections to apply this section for walls to the ceiling membrane. Is there any validity of utilizing section 717.5.4 to omit ceiling radiation dampers and if so, how?






Thanks in advance.

 

[RLGA]

Is there any validity of utilizing section 717.5.4 to omit ceiling radiation dampers and if so, how?

No. Fire partitions are walls, and horizontal assemblies are floor/ceiling and roof/ceiling assemblies. You cannot use the requirements for one on the other.