What should I do if my filters look clean, but the air purifier indicates they need to be replaced?

If your machine has been set-up on Auto for several months and if your air has been perfectly clean, it is possible that the filters are still relatively clean when the "change filter" light tells you to change them. However, the filters are cleaning particles down to 0.3 microns that are not visible for human eyes so even though the filter looks clean, it might contain a fairly large amount of very small particles and pollutants on its surface.