I'm thinking ahead and I was looking into the Airstream filter, the HE Filter AS 140. It's $35 for one. I haven't done the airflow test, I will do it tomorrow to see if I need to change it, I clean often the pre filter. I noticed today my air flow is not as strong as it was ... Is there a way to clean the main filter? The manual says no because you might die, lol, its just sawdust and not nuclear waste... Where do you guys buy the filters? How often do you change them, I understand it depends how often you turn and shop conditions... I turn 7 days a week,, have cut my hours a little... I did try to search the forum, sorry if this was answered before. Aloha