What is the minimum damper rating required for 3-hour fire-resistance-rated assemblies?

For fire-resistance-rated assemblies, the ratings are established to ensure that building components can withstand a fire for a specified period without collapsing or allowing flames to spread. The minimum damper rating required for 3-hour fire-resistance-rated assemblies must match the fire rating of the assembly itself.

In this case, since the assembly is rated for 3 hours, the damper that is part of or associated with that assembly must also have a minimum fire rating of 3 hours. This ensures that the integrity of the fire-resistance rating is maintained and that the damper can effectively prevent the spread of flames and hot gases during a fire event for the duration of that rating.

Therefore, the requirement for the damper's rating aligns with the fire-resistance rating of the assembly, making an option with a lower rating insufficient to comply with safety standards and fire prevention protocols. Thus, the correct answer specifies a damper rating of 3 hours to ensure consistent protection in line with the assembly's fire resistance.