What is the minimum fire protection rating for a fire damper installed in assemblies rated less than 3 hours?

The minimum fire protection rating for a fire damper installed in assemblies rated less than 3 hours is 1 1/2 hours. This is specified in building codes and standards that govern fire protection and life safety in structures. The rating ensures that the fire damper can effectively contain smoke and flames for a sufficient duration, thus preventing the spread of fire and smoke through air ducts. Fire dampers are critical components in maintaining the integrity of fire-resistance-rated barriers, especially in buildings that require compliance with specific safety standards.

It's essential for fire dampers to provide a reliable level of protection for assemblies that are classified below a 3-hour rating because it dictates the overall effectiveness of the HVAC system under fire conditions. The choice of a higher rating, such as 1 hour or higher in this case, would not be necessary for assemblies rated below 3 hours, as it aligns with the principles of providing adequate fire stopping while also adhering to the relevant codes and regulations.