The frequency with which you’ll need to change your air filters will depend a lot on what type of filters you have. Some products should be changed as often as every 90 days, while others can go an entire year without replacement and still be effective.  The professionals who install your home air purification system can tell you how often it is recommended that you change your filter. However, depending on the pollution load that the filters in your house are required to handle, you may need to change them a bit more frequently than the manufacturer suggests.