The minimum opening size for louvers used for exterior wall intake air openings is 1/4 inch. Which of the following is the correct minimum opening size?

• A. 1/8 inch
• B. 1/4 inch
• C. 3/8 inch
• D. 1/2 inch

Answer: (B)

Exterior wall intake louvers must provide enough air for combustion and ventilation while keeping weather, pests, and debris out. The minimum opening size specified for these louvers is 1/4 inch. This size ensures adequate airflow without making the opening so large that it becomes a greater entry point for rain or pests. An opening smaller than this, such as 1/8 inch, would restrict airflow and could lead to insufficient combustion air or poor ventilation. Larger openings like 3/8 inch or 1/2 inch meet or exceed the minimum, but the question asks for the smallest acceptable size, which is 1/4 inch.