Spare/Replacement filter for Blue 221 Air Purifier, by Blueair. At Blueair, we go to any length to increase cleaning efficiency – even if it means putting spandex on our air purifiers. The fabric pre-filter catches larger particles, extending the life of the main filter. Just vacuum it or put it in your washing machine when it needs cleaning. Instead of making our pre-filter in only one color, you can choose from five vibrant fabrics. That’s way more fun! Match your personality or redecorate your room. Or buy all 5 and change colors according to your mood? All it takes is a few seconds!