fwiw - I had a nice chat with tech support at 3M a while back asking about supplies for the trades and about cleaning existing filters. I often washed my P100’s a few times when they got dirty. I learned that the dacron (?) fill they use has an electrostatic charge that gives many of their dust filters their ratings. Washing with water, or soap, or alcohol etc. greatly diminishes the charge and the micron rating. Instead he suggested using the filters, dirty or not, for as long as I could, until a reduction in air flow was noticeable. They had no idea when they can start suppling trade houses.