How do masks and ventilation affect the distribution of aerosols in indoor environments?

What is it about?

Every time we breathe, speak, sneeze or cough, we emit tiny droplets or “aerosols”. Those infected with SARS-CoV-2, the virus that causes COVID-19, may spread the virus through these aerosols. In this way, aerosols can increase the spread of COVID-19. This is why social distancing and face masks are recommended to control disease spread. But indoor environments pose a different challenge. The levels of aerosols exhaled indoors build up over time, and airflow causes them to circulate in that space. How effective are masks in this situation? Can they prevent us from inhaling these aerosols? Many studies have looked into the risk of COVID-19 transmission indoors. Others have examined the success of masks in stopping the inhalation of aerosols. The current study combined these two avenues. The authors created a breathing model using a manikin head and particle atomizer (a device that can produce aerosols). Then set this model in a large, sealed room to understand how the spread of aerosols is affected by: 1) face masks, and 2) ventilation settings. It was found that that even with a mask on, exhaled droplets could travel 2 meters from the source (which was the breathing model). Only highly efficient masks like R95 and K95 masks provided enough filtration (60% to 46%) to reduce the risk of disease transmission indoors. Finally, they found that proper ventilation and air change significantly reduced the risk of transmission.

Featured Image

Photo by Ian Taylor on Unsplash

Photo by Ian Taylor on Unsplash

Why is it important?

This study demonstrates the spread of exhaled aerosols in a closed and ventilated environment. It also points out which masks available in the market are good at filtering aerosols. These insights can prove quite useful when framing disease control guidelines for the public. KEY TAKEAWAY: In an indoor setting with low ventilation rates, exhaled aerosols can be found even at a distance of two meters from their source. The use of highly efficient masks like N95 or K95 masks is recommended to prevent inhalation of these aerosols.