Finally, consider a recently published study , in which researchers carried out, under laboratory conditions, several well-controlled experiments with masks. What did they conclude? First, that efficiency varies greatly. Surgical or cloth masks, which are used by the vast majority of people, provide only 10-12% filtration efficiency. Masks known as respirators are more efficient, but none of them achieve more than 60% filtration, even under optimized laboratory conditions.
The second and most important conclusion is that even relatively low room ventilation reduces the accumulation of viral aerosols, and protects as well as the best available masks (N95 and the like). In other words, ventilating a room is still the best way to prevent Covid-19 transmission.
If instead of the obsession with masks, which, as we have seen, are mostly ineffective in the real world and lead to a false sense of security, there were campaigns to improve ventilation in closed spaces, how many Covid-19 transmission events could have been prevented and how many lives would have been saved? Unfortunately, most authorities chose instead the path of mask mandates, despite the lack of trustworthy evidence.