A while back, I posted data I collected from places around Beijing showing that indoor air is consistently cleaner than outdoor air. When I analyzed that data, I excluded places that allow smoking, but I’m posting the data here now:
Even on days where outside air was bad (AQI ~ 180), the air was even worse in the cafes that allow smoking. This is even more surprising because:
- I was not sitting in the smoking section.
- The smoke was not very noticeable. (I hate smoking, but the air seemed good enough to me that I sat there and worked.)
My guess is things are much worse in smoky bars and clubs, where the smoke is so thick my clothes smell like smoke the next day.
Conclusion: Indoor air is better than outdoor air in China, but you lose any advantage once people start smoking–even if you’re in the non-smoking section.
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.