Learn more. In our tests, we gauge how well an air filter removes dust, pollen, and smoke from the air, and see how freely air flows through the filter at any fan speed. We also calculate the ...

Over time, a worn-out filter could worsen the air quality in your home and reduce the effectiveness of your furnace. If your ...

lack of airflow will cause the furnace to overheat and shut down. Similarly, a dirty filter can stop an air conditioner because the coils freeze up due to inadequate airflow. Both issues stress ...