Dr. Douglas McMahon with the Allergy and Asthma Center of Minnesota says many parents of his patients with asthma are concerned, some are even asking about mask exemptions. McMahon has asthma himself and decided to measure his oxygen levels on the ice and on an exercise bike with and without a mask on. "Even with intense exercise in the cold air, it was 20 degrees outside, my levels were at 97% with a mask. Without a mask, the results were almost identical," he said. kstp.com/coronavirus/twin-cities-doctor-puts-masks-to-the-test-while-being-active/5974579/?cat=11854 #MaskUpMN