What color flame indicates proper combustion in a gas furnace?

A blue flame in a gas furnace is indicative of proper combustion. This coloration signifies that the gas is burning completely and efficiently, resulting in a clean burn that produces minimal carbon monoxide and other harmful byproducts. The presence of a blue flame indicates that there is a proper air-to-gas ratio, which is essential for optimal furnace performance.

In contrast, flame colors such as red or yellow suggest incomplete combustion. These colors typically indicate that there is insufficient oxygen available for complete burning, potentially leading to higher levels of carbon monoxide, soot, or other pollutants, which can pose safety risks. A green flame, while not commonly associated with gas combustion, can indicate the presence of certain materials or chemicals that should not be part of the combustion process. Therefore, a blue flame is not only the hallmark of efficiency but also a critical safety indicator in gas furnace operation.