With all the talk these days of air pollution and air purifiers, you might not realize there is a difference between an air purifier and your home air filter. Regardless of whether you own an air purifier your heating and air system is equipped with air filters. These air filters need to be changed at least twice a year. In fact some experts recommend that you change your air filters every three months. If you’ve ever changed your air filter the first thing you need to do prior to changing his make sure you know the correct measurement. Air filters come in many different shapes and sizes and if you select the wrong one it will do no good. Air bear filters come in many shapes and sizes and are suitable for most homes.