I cleaned frequently when I started CPAP years ago, but I always noticed a strong dusty smell whenever I took my CPAP on vacation. No amount of cleaning the mask, tubing, humidifier or changing filters would help. I ended up buying a new CPAP imagining built up dust, grunge or even mold inside my machine. After 3 months, I took my new CPAP on vacation. I noticed the same strong dusty musty smell when I went to sleep that night at the hotel. I never notice a musty smell in my home. I am not a great housekeeper, but I keep my nightstand and CPAP mask and tubing clean. I thought about buying the SoClean until I realized it only cleans the hose and mask - not the internal workings of the CPAP itself.
PROBLEM SOLVED! The last time my mom was in the hospital, they put an inline bacteria filter on her bipap. I decided to try it and bought one for about $2 on ebay. (It was $10 to $35 at the CPAP supply stores.) WHAT A DIFFERENCE! After about a month, the in-line filter was dark grey on the side nearest the CPAP and white on the side attached to the hose and mask. The inline filter obviously caught dust the manufacturer filter did not catch. I just got back from traveling out of town. For the first time, no musty smell. I also notice that I have far less sinus congestion, infections or colds, so it must be catching bacteria and maybe even viruses.
My new routine is to clean or change my hose every couple months. I flick dust off the manufacturer filter when I think about it and replace it when it looks dirty. My mask leaks a little air when it gets oily, so I wash it when I think about it which is usually when it makes air leak noise. I don't bother with distilled water. I just wipe out the chamber when I add more water and clean the humidifier chamber with a little vinegar solution to disinfect once or twice a month. The vinegar dissolves the cloudy calcium deposits. I change the inline in-line bacteria filter every 4-6 weeks.