INTRODUCTION High-flow nasal oxygen (HFNO) and non-invasive ventilation (NIV) may reduce the requirement for invasive ventilation in selected patients with respiratory failure.  However, there is concern that, when used in the treatment of coronavirus disease 2019 (COVID-19), both modalities may increase the risk of transmission to healthcare workers (HCW) through small droplet aerosol generation.  Small droplet aerosols have the potential to remain airborne for extended periods of time, follow air currents within the room, and penetrate deep into the airways, facilitating airborne viral transmission.1 Uncertainty about the relative risk of aerosol-generating procedures (AGP) has contributed to strikingly different recommendations amongst international guidelines on their use.  Much of the evidence concerning use of NIV and HFNO in COVID-19 patients come from experiences with two previous coronavirus outbreaks, the 2003 Severe Acute Respiratory Syndrome (SARS) epidemic and the 2012 Middle Eastern Respiratory Syndrome (MERS) epidemic. The potential for airborne transmission of a