We have Hepa filters built into our AC/Heat system. The filters are very expensive, but we only replace them 3-4 times a year. The directions are for twice a year, but with three big, hairy dogs and two cats.....
I can actually tell when theyneed replacing.
Skin kids - Jason, Kevin, Allison
Canine kids - Bennett & Bailey (always in our hearts), Riley, Banker, Rogue and Boz
Feline kids - Zoey, Talley and Abra