The effect of respiratory activity, ventilatory therapy and facemasks on total aerosol emissions

Background Exhaled respirable aerosols (<5 µm diameter) present a high risk of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) transmission. Many guidelines recommend using aerosol precautions during ‘aerosol generating procedures’ (AGPs) and droplet (>5 µm) precautions at other times. However, there is emerging evidence that respiratory activities such as cough and not AGPs are the important source of aerosols.