No, the S8s are supposed to do so. It is to help "dry out" any humidity "left over" from the night's session. It used to drive me nuts at first. I'd turn it off, get dressed, whatever, walk back in the room to make the bed and there it would be running away quietly and so I'd turn it off again. And again. And again. *giggle* Once in a while it pays to read the Users Manual. (I didn't , I learned about this in one of the apnea support forums *red-face*).
What I do to hurry the process along is tip the humidifier lid up. Removing the humidifier tank also helps shorten the process.
THX for replies. Was loaned the S8 by DME while my APAP is serviced.
Unfortunately, Blue Cross will not repair or replace my 3 yr unit for ANOTHER two years!