Him building a wall is pointless. Him wearing anything less than a properly fitted n-95+ mask without valves is also pointless in the environment he will be in, especially if the hvac does not have a way to kill virus such as a UV-C light in the intakes.
The point of the masks are to prevent the spread of the disease. The disease spreads best in an enclosed environment were one spends 15 minutes plus with an infected individual in close proximity. Problem is masks do very little good given the current usage patterns. Most masks are barely more than face coverings that do little to stop anything, as they are neither properly fitted, of the necessary filtration capacity and generally not sanitized regularly if at all.
Both sides of this issue are fools. The maskers for thinking masks of any variety are the universal cure all to prevent the disease when they are proven not. The anti maskers are foolish for thinking masks are universally pointless when that has been proven false as well. Masks of the proper type should be used properly when it is appropriate and necessary, namely enclosed spaces where the airflow is minimal and the hvac does not have the ability to sanitize the recirculated air and one will be there for longer than a few minutes. Otherwise masks are of very limited value.
The mask argument is the stupidest one I have seen with both sides having little clue of which they speak. I personally dont wear a mask, unless I go into enclosed building with high traffic. The masks I use are the 3M manufactured model 8210 construction and painting valve less N-95 disposable , which is one of good quality and known reliability. I wear it properly with a shaved face and sealed around the mouth.
Ranking the 14 face masks tested in Duke University study
