content: It does work and keeps the air fresh - I didn't change mine for literally years (I would take it out and hand clean it periodically which I don't think hurts anything, but finally I decided I had better get a new one.It is quite easy to remove and put back in, no problem there, seems a simple process.Seems tremendously expensive when you see what it is - but maybe there's something I'm not understanding in the technology of making it. As I said though I did go several years (more than 5, with regular use), before I replaced it. Cheaper than a whole new air purifier.