The rubber knob pops out with a toothpick, then press it back in after cleaning...careful , its small & can pop out and fly through the air LOL.You can see where it has a lip on one end that keeps it in place~My brand new one got stuck once already! Have read about it in forum but some swear it's no problem. How do you clean button? I didn't know how to take apart so blew air through it. It's ok for now...