Conclusion
In summary, large droplets settle quickly in the vicinity of the
ejection point with little drying, whilst small droplets, less than
about 100 µm, quickly dry and remain airborne. This has two major
implications for public health: firstly, safe distance is
considerably longer than the generally-recommended two metres, as the
virus remains fully suspended in air. Secondly, mask filters available
to the public are inefficient in preventing SARS-CoV-2 spreading, as it
is most penetrative through fabric filters. They can retain the droplets
from nasal and throat secretions on coughing and sneezing, but cannot
protect a person from inhaling nearby viruses released into the
atmosphere. The deadliness of this virus has drawn deservedly great
attention of the scientific community on its spreading mechanism, with
the latest re-evaluation of the basis adopted by the World Health
Organization and other agencies (9).