Outdoor combustion air obtained through one-permanent-opening method should have a minimum free area of what size?

The correct answer indicates that outdoor combustion air obtained through the one-permanent-opening method should have a minimum free area of 1 square inch per 4000 BTU/hr. This standard is established based on safety and efficiency considerations for appliance operation.

When appliances use combustion air from the outdoors, it is crucial to ensure that there is adequate airflow for proper combustion and to prevent potential issues such as incomplete combustion or the buildup of harmful gases. The ratio of 1 square inch of free area for every 4000 BTU/hr helps to ensure that there is sufficient air supply relative to the heating capacity of the appliance.

This specification serves to balance the need for effective combustion while also minimizing the size of the vent openings, thus contributing to overall building safety and energy efficiency. It reflects recognized standards in the industry, ensuring that appliances function optimally in various environmental conditions.

Understanding these parameters is essential for technicians in the field as they assess and install combustion appliances. By adhering to these guidelines, technicians can help ensure safety and compliance with local codes and regulations.