On Thursday, CDC Director Dr. Rochelle Walensky said the agency is considering revising its mask guidance.

“We’ll be looking at the outdoor masking question, but also in the context of the fact that we still have people who are dying of Covid-19,” Walensky said on NBC’s Today Show.

To Mask or Not to Mask?

As with most Covid-19 discussion, the evidence on whether it’s advisable to wear masks outdoors isn’t black and white, and should be based on a variety of factors such as vaccination status and community transmission rates.

“If you’re vaccinated and not in a vulnerable category, it’s probably fine not to wear a mask outdoors,” Linsey Marr, an expert on the airborne transmission of viruses at Virginia Tech, told CNN in an email.

For unvaccinated people, Marr recommends masks in situations when people are clustered closely together, like in a bar, a crowd or a line.

“If you’re unvaccinated and constantly passing by people close enough that you can reach out and touch them, then you should wear a mask,” Marr told CNN.

Vaccinated or not, an important factor in deciding to unmask outdoors is the levels of transmission and positivity in your area, Gupta said.

“The real question you need to try to answer is, what is the likelihood I’m going to breathe in someone else’s air? That’s basically it. The number of people, type of setting and what is the overall viral spread in their community,” Gupta said.