What is the term for air naturally available to an appliance?

The term for air naturally available to an appliance is referred to as combustion air. This air is essential for the proper combustion of fuels within heating appliances, such as furnaces and water heaters, as it provides the necessary oxygen required for the combustion process.

In residential and commercial settings, combustion air can enter through natural openings in the structure, such as cracks around doors and windows, or intentionally designed openings. This is critical because adequate combustion air is necessary to ensure complete fuel burning, which minimizes emissions and maximizes efficiency. Understanding this concept is vital for professionals working with gas appliances to ensure they operate safely and effectively.

While infiltration refers to unwanted air entering a building, and makeup air pertains to fresh air introduced to replace exhausted air, the specific focus here is on the air that directly supports the combustion process, which is why combustion air is the correct term. Ventilation air, while also important, relates more to maintaining air quality and temperature rather than supporting combustion specifically.