If everyone kept 6 feet or more from others, and avoided more than a few moments of close contact with anyone, and if everyone wore masks, and if when people gathered indoors there were not too many people, and if there was good air ventilation and/or good air filtration, then we’d do better than we’re doing now by a lot. Point being: It’s not sufficient to put a time and a distance on the exposure risk; one has to consider the other factors. I love the cigarette smoke analogy. If you’re in a situation where you’d smell others smoking if they were smoking, you’re at risk. More smoke for longer duration, more risk.