PM2.5 concentrations of outdoor tobacco smoke at different distances from the smoking source: Is there an optimal distance for a designated smoking area?

Outdoor tobacco smoke (OTS) level was determined by PM2.5 concentration. The OTS levels significantly exceeded 0 µg/m3 at every measured distance up to 21 m. In the regression model, OTS levels notably correlated with distance and wind speed. OTS levels diminished as distance expanded and wind speed reduced.