What is the minimum size hole required in a fire wall for a fire damper ordered as 32X18?

The minimum size hole required in a fire wall for a fire damper that is ordered as 32 inches by 18 inches takes into consideration the overall dimensions of the damper and the need for clearances necessary for proper installation and operation. When a damper is specified, it is important to allow for some extra space to accommodate the damper's outer casing, which typically has to be fitted into the wall snugly, allowing for any necessary adjustments or expansion.

In this case, the correct answer is 32 3/8 inches by 18 1/4 inches. This size provides the additional clearance needed around the damper itself. The 1/8 inch extra in width (32 inches to 32 1/8 inches) and the additional 1/4 inch in height (18 inches to 18 1/4 inches) allow for installation tolerances, ensuring the damper can be easily installed without being squeezed too tightly by the wall opening. This extra sizing is critical for ensuring that the damper operates effectively and is not hindered by any obstructions.

Proper installation is essential in maintaining the integrity of the fire wall and ensuring the damper functions correctly in fire safety situations. Therefore, understanding the required