What is the minimum fire damper rating required for a 1 hour fire-resistance-rated assembly?

For a 1-hour fire-resistance-rated assembly, the minimum fire damper rating required is indeed 1 hour. A fire damper must be rated to at least match the fire-resistance rating of the assembly it is installed in to effectively limit the spread of fire and smoke through ductwork.

Choosing a rating higher than 1 hour, such as 1.5 hours or beyond, would not align with the requirements since it would exceed the necessary specification for that particular assembly, while a rating that is too low would not provide adequate protection. Thus, the correct choice reflects the need for the fire damper to have a performance level that corresponds directly to the fire-resistance-rated assembly it serves.