The virus spreads by three possible ways: by respiratory droplets, aerosols, and through contaminated surfaces – as explained in greater detail by the CDC. 

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Respiratory droplets, including small bits of saliva and respiratory fluids, are propelled through the air – mostly when an infected individual coughs or sneezes. They fall to the ground after traveling 3-6 feet (hence the recommendation for a social distance). Published research, which has been replicated, shows that when it comes to talking in close proximity, droplets are less important than aerosols.

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Aerosol transmission is similar to droplet transmission with one key exception – the bits of respiratory fluids are much smaller and can linger in the air for much longer, from minutes to hours. Therefore, being in a small indoor space together with many other people and without good ventilation presents a higher risk of contracting the virus. Aerosol transmission is the main component in spreading measles and chickenpox, and at least a strong contributor to the transmission of tuberculosis and influenza. Many scientists believe that the same can be stated about Covid-19.

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Face masks provide various degrees of protection against droplets and aerosols in the contaminated air. As they muffle speech, a person naturally tries to speak louder, whereby exacerbating the problem of a forceful exhalation.

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While N95 respirators are best when fitted properly, it is difficult to breathe while wearing this mask, especially for a long period of time. Because of this, they are not used frequently. Surgical masks and cloth masks are used by most people for everyday activities when around other people. While these products can limit the droplets, aerosols can pass through easily, both for inhaled as well as exhaled air. Basically, with masks: Easy breathing = Easy passing of aerosols
 

The ActivAir provides full protection against both forms of airborne transmission, via droplets as well as aerosols. It features a first-ever wearable active disinfection chamber designed to destroy the virus in the passing air stream. Once disinfected, the air stream is directed towards the face of the user providing a personal source of continuously supplied virus-free breathing air. The user can breathe easily without exerting an effort to move the air through a mask filter.

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References: 

1. Covid-19 is transmitted through aerosols. We have enough evidence, now it is time to act. Jose-Luis Jimenez. Time magazine, August 25, 2020. Link

2. Particle sizes of infectious aerosols: implications for infection control. KP Fennely. The Lancet. Respiratory Medicine, 2020. Link 

3. Identifying airborne transmission as the dominant route for the spread of COVID-19. Renyi Zhang, Yixin Li, Annie L. Zhang, Yuan Wang, Mario J. Molina. Proceedings of the National Academy of Sciences Jun 2020, 117 (26) 14857- 14863; DOI: 10.1073/pnas.2009637117 Link

4. How face masks can help prevent the spread of Covid-19. Diana Kwon. The Scientist. July 8, 2020. Link

5. Visualizing the effectiveness of face masks in obstructing respiratory jets. Siddhartha Verma. Manhar Dhanak, John Frankenfield. Physics of Fluids. 32, 061708 (2020) Link