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

The minimum damper rating required for penetrations of 3-hour or greater fire-resistance-rated assemblies is indeed 3 hours. This requirement aligns with the principles of fire safety and prevention, as established in building codes and standards.

When fire-resistance-rated assemblies are designed to contain fire for a specified duration, any openings or penetrations through these assemblies must be adequately protected to maintain the integrity of the fire barrier. A damper rated at 3 hours ensures that if a fire occurs, the damper will perform effectively within that time frame, preventing the spread of smoke and flames through the penetration.

This requirement underscores the importance of using properly rated fire dampers in critical applications where maintaining fire resistance is crucial to the safety and protection of the building and its occupants. Choosing a damper with a lesser rating would not provide adequate protection and could compromise the effectiveness of the fire-resistance-rated assembly.