Daniel Berger, EMT, published a recent article in The Journal of Emergency Medicine comparing different marks types for healthcare professionals reported that fluid resistant surgical masks (level 3) provided filtration at a smaller particle size than the N95 respirator and proved sufficient at filtering of aerosol and droplets associated with bacteria and viruses like COVID-19 and influenza.
An ASTM Level 1 face mask filters out ≥ 95% of bacteria and ≥ 95% of 0.1 µm particles and provides fluid resistance
Level 2,3 provides a higher level of filtration and therefore respiratory protection.
If the CDC and WHO are correct and COVID-19 is only spread by droplets, or the studies on influenza infection and mask use are applicable, then a simple fluid resistant face mask should provide sufficient protection.
Traditionally, droplets are defined as large (>5 microns) aqueous bodies.
Perfumes are less than 1 micrometer in diameter and that is why you can smell perfume through an N95
Talc Powder demonstrated a median diameter of 26.57 μm which is used to test for particulate matter.
A proper fit of the mask through fit testing is important since aerosols can escape thru the sides of the mask.
The one-way valves seen on some N95 masks are the industrial variety and protect the person wearing it from particulates but not others around them.
