If the conclusions about masks is this study are true, that means most indoor spaces and just being around gas powered devices for the same time periods, or being in your car with 3 other people is dangerous to your health.
Most places that are not outside away from a co2 source, that do not have high air exchange rates have high co2 concentrations.
Most places that are not outside away from a co2 source, that do not have high air exchange rates have high co2 concentrations.