Lab tests for Spunbond Polypropylene masks
I mailed three washable masks to a lab in North America for testing. We've got some amazing results back!
Note: Aaron Collins has previously tested three similar masks from the same batch of Smart Fab (Spunbond Polypropylene - SBPP). Details here. Aaron's masks were 4, 8 and 12 layers of 38 grams-per-square-meter (GSM) SBPP with and outer layer of poly-cotton.
The masks to this new lab were 8, 12 and 16 layers of the same SBPP (304, 456 and 608 GSM) and no cotton outer. That's a far better strategy for these masks if high filtration is what you're aiming at.