So, I was bored today. Flat out bored. So I did this. The hepa filter from my research is about the same as level 3 mask fabric. Print time is 3.3 hrs. Procurement of filter material was courtesy a rigid shop vac hepa filter, elastic from wife’s sewing basket, rubber band. It breaths ok if your at rest, but the minute you need a lot of volume, it won’t work.