Effect of ventilation and wearing a facemask in reducing indoor aerosol transmission

The COVID-19 pandemic has significantly disrupted research in respiratory protection and transmission routes. Indeed, the pandemic has highlighted a number of issues, including those related to the performance and use of respiratory protective equipment such as masks and ventilation. A plethora of commercial and homemade masks have widely appeared during the pandemic, although they are not yet fully regulated in performance and fit test. However, with regard to the source reduction process, testing facemasks not at the inhalation, but at the source (exhalation) offers a new perspective on how to prevent particle emissions. Different means of transmission reduction are measured and analysed here, and different conditions were compared: the ventilation environment, the type, filtration properties and fit (leaks) of three different facemasks. It was found that ventilation greatly helped reduce the wearer’s emissions at source. Additionally, while some materials are certainly more effective than others at inhibiting particle penetration, an even more important factor is the amount of leakage emitted from a mask.