I don’t really leave the house that often, mostly to walk the dog, but I don’t then cuz it’s a huge open air space.
I do on the bus because of how confined it is and how many people use/touch it, but besides that I have no idea.
Do you always have to wear a mask in these places? Or just when there is a covid spike?
How do you even know when there is a covid spike for that matter?
Additional question what level of indoor air filtration would it take to not need indoor masking?
most likely a level you’re never going to encounter tbh. I wouldn’t spend time trying to figure out when it’s safe to unmask inside
this (unverified, honestly very questionable IMO) graph from back when more people were pretending to care, advocates for at least 4.5 full air changes per hour. My guess is even that won’t matter for close contact spaces, but if some distance can be maintained maybe just aim as high as you can feasibly get.
https://www.pnnl.gov/news-media/faster-air-exchange-buildings-not-always-beneficial-coronavirus-levels this is also interesting regarding whole-building ventilation systems.
but yeah if you have a properly rated hepa filter with a good CFM exchange in a single room like 500sq ft you can achieve meaningful reductions, but its probably not as good as an N95 unless you go crazy with it. Probably better as another layer for situations where you have to cohabitate than a replacement for masking, esp since doing 5,10,etc air changes per hour basically requires loud fans running at full blast.