People infected with COVID-19 produce many small particles that contain the virus as they breathe out. These particles are called aerosols – droplets in the air that come from our mouths when we talk, breathe, cough, or sneeze. Some of these will be inhaled almost immediately by people close by (less than three feet away). The rest of the particles are spread out over longer distances and can still be inhaled by others further away (more than six feet). The larger particles at a short distance are called droplets. The smaller particles at longer distances are droplet nuclei. Both of these different-sized particles are still aerosols because they can be inhaled directly from the air. Masks usually block large droplets from landing on covered areas of the face. Masks are also partially effective against inhaling aerosols. This is very important to reduce the risk of catching COVID.

Low possibility of spreading the virus after touching surfaces

Wearing masks, keeping your distance, and limiting the number of people indoors all reduce the risk of catching COVID-19, whether through less direct contact with surfaces or droplets, or from inhaling fewer aerosols. However, there is also a need for better air flow in buildings. This is because the tiniest suspended particles can stay in the air for hours. This makes opening windows or installing or upgrading heating, ventilation, and air conditioning systems very important. For example, people are much more likely to become infected in a room with closed windows or without a ventilation system.

Importance of improving indoor air flow and air quality

COVID-19 may become seasonal, and we may have to live with it as we do with influenza. Safer indoor environments are required, not only to protect unvaccinated people and those whom vaccines have not protected, but also to slow down vaccine-resistant variants or new harmful air particles that may appear at any time.


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