What environmental factor can affect gas furnace performance?

High humidity levels significantly affect gas furnace performance primarily because they can influence combustion efficiency and the ability of the system to properly ventilate. When the humidity is elevated, the air holds more moisture, which can lead to condensation in the combustion chamber and ductwork. This not only creates potential issues with water damage but can also cause burners to operate inefficiently.

Moreover, high humidity can affect the overall air quality and circulation within your heating system, making it more challenging for the furnace to maintain a consistent temperature. In extreme cases, this imbalance can lead to the production of harmful byproducts if not adequately vented, as the combustion process may not effectively utilize the available oxygen, resulting in incomplete combustion.

In contrast, other factors like low oxygen levels and extreme cold weather generally do not have the same pronounced effect on gas furnace performance as humidity does. While high altitudes can lead to minor inefficiencies due to thinner air and reduced oxygen, the primary concern with high humidity presents a more direct and observable impact on how gas furnaces operate and maintain efficiency.