What is the function of an air filter in a gas furnace?

The function of an air filter in a gas furnace is primarily to remove dust and debris from the air before it enters the furnace. This is crucial for a few reasons. First, clean air is essential for the efficient operation of the furnace, as contaminants can clog the burners and heat exchangers, which can lead to decreased heating efficiency and increased wear on the system.

Furthermore, by filtering out dust, pollen, and other particulates, the air filter helps maintain better indoor air quality, which is important for the health and comfort of the occupants in the home. A clean filter allows for proper airflow, ensuring that the furnace can operate as designed.

While enhancing heating efficiency is a consequence of having a clean air filter, it is not the primary function of the filter itself. Similarly, air filters do not control humidity levels, nor do they provide insulation against heat loss; those functions are served by other components of the heating system or home design.