KEY POINTS
  • The risk of being exposed to Covid-19 indoors can be as great at 60 feet as it is at 6 feet in a room where the air is mixed.
  • Existing safety guidelines have omitted too many factors to accurately quantify the risk of airborne transmission, such as time, mask use and ventilation rates.
  • Bazant and Bush question long-held Covid-19 guidelines that recommend 6 feet of distance between people.
Customers dine at Picos Restaurant, which received threats following their announcement of continuing to require masks, as the state of Texas prepares to lift its mask mandate and reopen businesses to full capacity during the coronavirus disease (COVID-19) pandemic in Houston, Texas, March 9, 2021.

The risk of being exposed to Covid-19 indoors can be as great at 60 feet as it is at 6 feet in a room where the air is mixed — even when wearing a mask, according to a new study by Massachusetts Institute of Technology researchers who challenge social distancing guidelines adopted across the world.

MIT professors Martin Z. Bazant, who teaches chemical engineering and applied mathematics, and John W.M. Bush, who teaches applied mathematics, developed a method of calculating exposure risk to Covid-19 in an indoor setting that factors in a variety of issues that could affect transmission, including the amount of time spent inside, air filtration and circulation, immunization, variant strains, mask use, and even respiratory activity such as breathing, eating, speaking or singing.