There’s an extremely wide range of viral expulsion rates, both from person to person, and from day to day for a single person. You really have to think about t

There’s an extremely wide range of viral expulsion rates, both from person to person, and from day to day for a single person. You really have to think about things logarithmically. There’s some viral concentration that is enough to infect you 50% of the time, but most of the time, the actual concentration is either way higher than necessary or way lower than necessary. The types of masks most people use and the way they wear them maybe filter 70-80%. That’s about 0.5 on a log 10 scale. That will make a difference sometimes, but not that often if the experienced variation in concentration is maybe 4-5 orders of magnitude for a positive person. If you’ve got someone sick in your house and you don’t want to get covid, you need to do high quality masks on everyone, fans blowing out windows, air filters, intelligent HVAC operation, etc. If you do all of that you can probably get 3 orders of magnitude reduction and likely keep it from getting everyone in the house.