Our 1 inch pre-filter for the 500-650 CFM models are effective at filtering course particulates in the air equal or greater than 10 microns. These pre-filters help serve to give longevity to the primary filters which have a much higher efficiency rate for particulates as small as 0.3 microns. These filters have a G4 efficiency rating, meaning they can filter at 90% efficiency at ≥ 10 um. These filters are replaced on a much more regular basis than its primary counter part. Ensure pre-filters are changed when they look dirty. Usage may vary depending on heavy use (such as high concentration of airborne particulates). If you have any enquiries about the frequency of replacement, feel free to contact us through our website chat, call us on our number or pop in at our Murarrie show room to have a chat. Compatible Air scrubbers: IAQ Pro AS650 air scrubber Drieaz 500 CFM air scrubber Thorair 500 CFM air scrubber
