Is Outside Air Covid Safe? Are Masks Needed Outdoors?

In my mind, it really depends on how many viral particles are needed to cause an infection. If it’s a very small number, then dilution does more harm than good because the infectious plume is larger. If it’s a large number, then dilution is very helpful because the concentration very quickly falls below the critical point.

The author breezily says that 500 ppm at an outdoor restaurant is “pretty good”, but we have no way of know if that would be over or under the critical concentration of viral particles. The epidemiological data suggests that eating at restaurants, whether indoors or out, is a strong predictor of infection.

Personally, I don’t wear a mask if I’m walking around my suburban neighborhood and can cross to the other side of the street to avoid other pedestrians. I carry a mask when I go hiking on trails where I’m likely to run into other hikers going the other way on a narrow track. I wear a mask if I’m going into a central shopping district or outdoor market. And I only eat at outdoor restaurants if the tables are truly outdoors, not in a tent, and are 10+ feet apart.