At what altitude must gas furnaces have adjustments to operate properly?

Gas furnaces need to have adjustments to their operation at higher altitudes due to changes in atmospheric pressure, which affects the amount of oxygen available for combustion. At sea level, gas furnaces are calibrated to work with a specific air-to-fuel ratio. As altitude increases, the lower air pressure means less oxygen is available, potentially resulting in incomplete combustion if the furnace is not adjusted accordingly.

Typically, manufacturers and industry standards suggest that adjustments may be necessary starting at around 2,000 feet above sea level. This altitude is important because, beyond this point, the performance and safety of the furnace can be compromised if it continues to operate with the original sea-level calibration. Therefore, ensuring that gas furnaces are adjusted at or above this altitude is crucial for efficient operation and to minimize risks associated with improper combustion, such as the production of carbon monoxide.