You always questions whether the air purifiers are actually doing anything but let me tell you, when I took out that old filter to replace it...I will never question it again. Oh my lord, that thing was darker than my taste in music. Filter was super easy to replace, just turn the purifier upside down, twist/click the bottom off, take the old one out, and put the old one in. Job done. Very happy with my purifier and the filter systems 😊