For a fire-resistance rated assembly of less than 3 hours, what is the minimum damper rating?

• A. 1 1/2 hours
• B. 3 hours
• C. 2 hours
• D. 1 hour

Answer: (A)

Dampers that pass through fire-resistance rated barriers are chosen to maintain the barrier’s fire performance. When the surrounding assembly is rated for less than three hours, the minimum listed fire rating for the damper is one and a half hours. This ensures the damper’s enclosure and seals contribute a meaningful level of fire resistance for the duration of the fire exposure, helping prevent flame and heat from crossing the barrier via the duct. A damper rated only for one hour wouldn’t meet the minimum for these cases, while a two-hour or three-hour rating would exceed the minimum but isn’t necessary to satisfy the requirement. Therefore, the lowest acceptable damper rating in this scenario is one and a half hours.