Here's an excellent breakdown of coronavirus exposure risk scenarios

"As we are allowed to move around our communities more freely and be in contact with more people in more places more regularly, the risks to ourselves and our family are significant. Even if you are gung-ho for reopening and resuming business as usual, do your part and wear a mask to reduce what you release into the environment. It will help everyone, including your own business." -- Dr. Eric S. Bromage

https://www.erinbromage.com/post/the-risks-know-them-avoid-them

Image from CDC.gov -- https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/diy-cloth-face-coverings.html