Ace the HVAC Journeyman Challenge 2026 – Cool Skills, Hot Success!

The correct approach to determining the required size for combustion air openings in a confined space appliance revolves around understanding the relationship between the input rating of the appliance and the necessity for adequate combustion air supply. In a confined space, the appliance requires a specific amount of fresh air to ensure complete combustion and to prevent the buildup of harmful gases.

The requirement of 1 square inch per 5,000 Btu/h is established in various codes and standards to promote safety and efficiency. This ratio ensures that for each 5,000 Btu/h of combustion input, there is sufficient air supply to support safe operation. A smaller opening would not provide enough air, potentially leading to incomplete combustion, increased emissions, and safety hazards, while a larger opening would be unnecessary and could lead to excess air which is also inefficient.

Understanding the importance of proper air supply is essential for HVAC professionals. An appliance that is starved of oxygen can produce carbon monoxide and other harmful byproducts, highlighting the critical nature of adhering to these guidelines for the sake of both appliance performance and indoor air quality.