Filters for the Blueair 201 and 203 Purification Systems should be replaced every six months to keep air purification at its optimum. Changing filters is easy: Just open the lid on your 201 or 203 model, lift out the old filter, and drop in the new one. No screws, hook, or tools to contend with. Used filters are 100% recyclable and don't release toxins into landfills or the air, so you can breathe easy!