Resmed has the answer online: 1 to 1 vinegar to water soak. I would avoid bleach as I would not want to breathe it. There are cheap replacement parts for your machine on Amazon new, and ebay has some as well.

A few weeks after I read my initial sleep study recommending a CPAP, I went out a purchased a used ResMEd S9 Elite, heated humidifier unit, a mask and heated hose. A month later, I called Apria Healthcare and asked them about the status of my doctor's Rx for me. They replied they could not contact m...