According to this news report about a MIT study, the 6 foot rule for indoor spaces makes very little difference. I have not read the entire paper, but I'm taking it with a grain of salt because it assumes that an indoor space will be well-mixed. On the other hand, there might be some truth to it.
>>>The widely used rule of staying 6 feet away from others does little to affect the risk of exposure to COVID-19 in indoor spaces, according to a new study out of MIT. . . .
A
website made available by the researchers shows how this model works in different scenarios.
For example, if an infected person walks into a classroom hosting 25 people, none wearing masks and all speaking, everyone would be at risk from the coronavirus within 36 minutes, the website says. It doesn't matter if they follow the 6-foot rule.
By contrast, if all 25 people in that room were wearing a mask, the air would be safe to breathe for 20 hours, it said.
If they were all singing without a mask, they be at risk from the virus within three minutes.<<<
https://www.yahoo.com/news/staying-6-feet-apart-indoors-112732760.html
>>>The Well-Mixed Room
We first characterize the evolution of the pathogen concentration in a well-mixed room. The assumption of well mixedness is widely applied in the theoretical modeling of indoor airborne transmission (
14,
16,
17), and its range of validity is discussed in
SI Appendix, section 1.<<<
Airborne transmission arises through the inhalation of aerosol droplets exhaled by an infected person and is now thought to be the primary transmission route of COVID-19. By assuming that the respiratory droplets are mixed uniformly through an indoor space, we derive a simple safety guideline...
www.pnas.org