The filters we carry at J&A have different levels of efficiency all rated by the size of particle they trap. We suggest talking to a comfort consultant to best identify what filter to purchase as your needs may vary. Good- The Healthy Climate Merv 11 is a standard filter ideal for homes with pets and lasts roughly 8 to 12 months, while the Better-The Healthy Climate Merv 13 is ideal for filtering out mold and some viruses and last roughly 8-12 months Best- The Healthy Climate Merv 16 is the highest level of particle filtration you can purchase. The Merv 16 filter includes a carbon core which will reduce ozone while trapping germs and virus and removes up to 95% of particles in your home. In addition to these options, J&A can also install Hepa filters to your ductwork to clean the air in your house to be as clean as the air in a hospital.