“I think the guidelines should be based on science and practicality,” said Dr. Marr. “People only have so much bandwidth to think about precautions. I think we should focus on the areas that have highest risk of transmission, and give people a break when the risk is extremely low.” Dr. Marr uses a simple two-out-of-three rule for deciding when to wear a mask. In every situation, she makes sure she’s meeting two out of three conditions: outdoors, distanced and masked. “If you’re outdoors, you either need to be distanced or masked,” she said. “If you’re not outdoors, you need to be distanced and masked. This is how I’ve been living for the past year. It all comes down to my two-out-of-three rule.” Use the 2-out-of-3 Rule To lower risk for Covid-19, make sure your activity meets two out of the following three conditions: outdoors, distanced and masked.