SignificanceAirborne respiratory diseases are transmitted via viruses in respiratory aerosol particles. The emission of such aerosol particles can increase by more than 100-fold from rest to maximal exercise and the risk of infection can increase by more than 10-fold, respectively. This study shows that age is another important factor that affects respiratory aerosol particle emission, as subjects aged 60 to 76 y emit more than twice as many aerosol particles at rest and during exercise and five times as much aerosol volume. This suggests that aerosol particle emission increases when the respiratory system ages.