Standard filters work to keep your system and ductwork clean, but they don’t effectively improve indoor air quality. To do that you need a media filter. The media filter rests between the main return duct and the blower cabinet and will improve dust and particle removal by seven times that of a standard filter. However, upgrading to a pleated media filter will remove everything from insecticide dust to airborne viruses from the filtered air. Always choose a filter that matches your blower’s capacity. For optimum efficiency and filtration, Ross & Witmer recommends that you replace your disposable filters at least once a month. If you have washable filters, they should be cleaned once a month.