If all combustion air is taken from the inside, where should the two permanent openings be located?

The correct answer is that the two permanent openings should be located within 12 inches of the top and bottom of the space. This configuration is crucial for ensuring proper ventilation and combustion air supply to appliances that rely on combustion, such as furnaces, water heaters, or boilers.

When combustion air is sourced from inside the building, it is essential to facilitate both air intake and exhaust effectively. The placement of the openings allows for a balance of air movement, where the warmer air tends to rise, making the top opening critical for allowing hot air and combustion gases to escape. Meanwhile, the lower opening ensures that cooler air can be drawn in from the space. By placing the openings within 12 inches of both the top and bottom, a more efficient flow of air can be maintained, which is vital for the safe operation of combustion appliances.

The necessity of positioning within this specified range is supported by building codes and standards, which are designed to optimize combustion efficiency and minimize the risk of back-drafting or the buildup of hazardous gases within occupied spaces. This strategic placement also helps in achieving effective circulation, which is essential for combustion processes to function safely and efficiently.