A particle measuring 5 microns or less and is light enough to float for hours in the air. They are mainly involved in airborne transmission of a virus and even minimal movements of air such as a small breeze can help carry away the aerosols containing viruses. Aerosols can transmit infection across distances.
For comparison, the diameter of the average human hair is about 70 microns so aerosolised particles are many times smaller and invisible to the naked eye.
Respiratory droplets are typically larger than 5 microns and fall to the ground within six feet or 1.8 meters from the source. Droplets and aerosols are the main modes of transmission of SARS-CoV-2. When an infected person breathes out, talks, sings, and/or coughs, they exhale aerosols and droplets containing millions of viral particles into the air. An uninfected person can become infected by breathing in these particles. This is why it’s recommended that people wear masks and maintain a safe distance from others to prevent infection.
Infectious Disease Respiration Transmission