3D style that looks pleated - 3 layers of 80gsm

 

Three ayers of 8o gsm  SBPP would be 70% filtrtion efficiency (ignoring side) leaks. 

This is airly easy to sew from a paper template. 

 

Those four Vs going into the mask from each side are where folds are made:

1. First a straigh line sew for each fold.
2. Then cut off the excess
3. Then zig-zag sew the edge to stop it fraying and tighten up the join.