A few layers of cotton is usually enough to filter 95%> of all 0.3 micron particles this is because the filtration is based on the fact that the thickness of the filter is orders of magnitude larger than the size of the particles so the size individual holes at any given layer don’t matter that much.
That said the majority of the benefit from this suit wouldn’t come from air filtering but from the fact that you won’t get contaminated droplets on your face and you won’t be able to touch your face with your hands after touching contaminated surfaces.
The median-fit factor of the homemade masks was one-half that of the surgical masks. Both masks significantly reduced the number of microorganisms expelled by volunteers, although the surgical mask was 3 times more effective in blocking transmission than the homemade mask.
The idea is that you can keep throwing out the outer suit but keep the rest.
- Source of clean air: HEPA filter will get contaminated and needs to be changed. UV sterilization might do it, but bulky and power intensive. Otherwise carry your own gases -- extremely technical, likely to asphyxiate yourself.
- As soon as you go I to a red zone the exterior of the suit is contaminated. Basically you need a disposable suit/gown outside the positive pressure suit.
Only other issue is that this is bonkers. Stay at home, wash your hands, wear a face shield when out to prevent touching your face if need be.