IAQS wants to highlight this interesting study. The authors measured the time for which small aerosol particles generated by a person exercising on a training bike persist in the air in an outpatient cardiology clinic. Aerosol persistence times were observed to vary greatly with the ventilation of the specific building or room. A risk analysis suggests that in order to prevent Coronavirus transmission by microdroplet aerosols, space ventilation is crucial and should be at least 10 air changes per hour. Portable air cleaners can contribute significantly to keeping the air free of aerosols and decreasing infection risks.