DENVER — Another day of air quality alerts across Colorado may throw a wrench in any outdoor plans. What poor air quality could mean for your workout in the Denver areaThe alert warns of multiple pollutants, staying in effect until at least 4 p.m. Thursday, with the highest concentrations of ozone in the southern and western portions of the Denver metro area. Some people might have what's called subclinical asthma, meaning it doesn't really cause a problem most of the time, but on really bad air quality days or with really strenuous exercise, you can start to notice some symptoms.” The National Institutes of Health estimates that 20-70% of people living with asthma are undiagnosed or untreated. Bad air quality mixed with physical exertion could cause those flare-ups.