Attempting a 99% mask - 600 GSM of SBPP

Four layers of 150 GSM Spunbond Polypropylene (unbranded, cut from a roll, from Amazon)

Small on the left, L on the right:

My own nose is "Norman" (high nose bridge). Not everyone is like that of course, so seemingly four straps for Rag Mask Max is more universal. I had to sew on four eyelets as the band needs to move to make that tight in use. Here's what that looks like in use (I replaced my own head with a cartoon equiv):

The top band goes fully around the head above the ears. The bottom band is the only one that ties - in a bow at high-neck level. All the fit is achieved with that single bow, and yes the seeming four straps are a singe strap threaded through four eyelets.  

This four layers of 150 GSM Spunbond Polypropylene (SBPP) hasn't been lab tested. If it holds to the same PFE as the 80GSM does, this should be 99.5% or so PFE for 300 nm particles art 28.3 liters per minute flow rate. 

If you had N95 or equivalent you'd prefer that I think.  If you can't afford that, then this quick to sew item should keep you safe until supplies kick in again. 

Apart from the actual PFE (verses estimated based on the curves from actual PFE for 80 GSM SBPP) it is also not known whether filtration drops for this source of SBPP or rises after washing.  The masks of the study linked to above - the PFE dropped with washing.  Ania Mitos (Maker Mask) tested a lower GSM SBPP that had PFE that went up after washing.

And this needs to be stated every time SBPP is suggested for masks - these are incredibly breathable - empty to lungs to full: half a second. Believe it.