The China Air Quality app has been a huge motivator for me recently in deciding whether or not to wear the mask. Depending on humidity, cloud cover, wind, and any number of factors the pollution here sometimes appears less severe than in reality.
Cycling for me is a primary form of exercise and I got tired of feeling like hell (short of breath, coughing, general malaise) after spinning around for a few hours. Most often I’d convince myself it looked fairly clear out and just scoff at donning the mask but with the app and the simple label “Unhealthy” I need to take precautions.
Chengdu’s pollution is also unusual. Unlike a lot of other infamous places (the whole NE of China, in particular Beijing), the pollution here just seems to stick around. It’s occasionally awful and rarely perfectly clear, but it’s there. Beijing you could hold out for the times you knew would clear up and be perfectly clean, but here you can’t time it like that.
My advice is if you do any marginally strenuous exercise outside for any period of time greater than a half hour regularly, use form of sanctioned protection. Sure you breath this stuff in most of the time anyway (unless you happen to work in a pressurized filtrated laboratory), but the time its really detrimental is when you’re exerting your lungs. Be safe!