The Winix c535 air purifier has a 3-stage purification system while the c555 has a 5 stage system. The Winix C555 air cleaner with plasmawave technology comes with a washable Advanced Odor Control (AOC). On the other hand, the carbon filter in the C535 cannot be washed -- you’ll need to buy replacements after some time. (this is not a Winix c555 vs c535 post)