Thank you folks for your replies. I thought, if filtration was a real problem, the CPAP manufacturers would've addressed it long ago.
Appreciatively,
Mike

Has anyone noticed a difference using a filter in the tubing?
Thank you,
Mike

First. thanks to all you folks for caring. Now, ChicagoGranny, trust me. It’s rust. I clean it every day with warm slightly soapy water, dry it and leave it opened until I fill it with distilled water at bedtime. Hey SleepGeek, thanks anyway but I’m not in to pink slime. I think I answered your ques...

Is this normal or am I doing something incorrectly?
Thanks in advance,
MichaelA