I know that, I did not really ask for advice, more for your experience. And since you do not have experience with oxygen, I was merely suggesting it, as I heard how it helps people with breathing problems and I do not see the need to have the masks 100% sterile if it is your personal mask. But I am also not a doctor ..
My personal experience is that you do need to diligently sterilize things like masks that only you use. I spent years boiling medical equipment daily.
I had a nebulizer for a time to administer inhaled treatments. It had to be carefully sterilized.
Failure to adequately sterilize your personal medical equipment is sometimes a source of very nasty antibiotic resistant infections.
Your own germs or not, once they leave your body and grow on a surface and come back in contact with you, you had better take it seriously as a threat to your health.
