Question about a duct penetrating a single floor of a 3A Library building where there is no requirement for separation of spaces from floor to floor but there is a requirement to protect the structure. NFPA 220 1.1 says that openings in floors and shaft enclosures are not related to the types of building construction and are regulated by other standards and codes. NFPA 90A 5.3.2 says that when a duct passes through a floor that is required to have a fire resistance rating then the duct needs to be enclosed or have a fire damper. Why would 220 exempt openings in floors if 90A just says to fire rate the duct? It seems like NFPA is requiring a rating of the structure and not the hvac system in 220.