Indoor Air Cartoon Journal, February 2020, Volume 3, #96

What makes the coronavirus a major public health concern? It is not only an infectious virus, but it is also a contagious virus. For example, A virus is infectious and not contagious when it can be passed on by a non-human origin to a human, but the virus can not be passed from one human to another. Contagious means the infectious virus can be passed from human to human. The morbidity and mortality of a contagious virus make it a major public health concern.

A contagious virus can be transmitted when a healthy person has direct or indirect contact with the person infected with a virus, is exposed to larger size particles sprayed through coughs or sneezes, or inhales airborne virus particles. Viruses that are of larger particle size fall easily on indoor surfaces. Virus particles generated through coughs and sneezes could be as large as 114µm and 360µm, respectively.

Viruses with smaller particle size float in the air. Breathing could generate particle size as small as 0.3µm or less. Such size makes virus particles, generated by breathing, float in the air for a more extended period at appropriate humidity and temperature.

The cleaning of indoor surfaces is adequate for viruses with a larger particle size known to have a higher deposition rate and not viruses with a smaller particle size that linger for a more extended period. Scientific evidence suggests that ventilation is effective in mitigating the spread of contagious viruses that remain airborne. The cleaning of indoor surfaces is not adequate for such purpose.

So, the question is, why is the use of appropriate ventilation rates in indoor environments, buildings, vehicles, airplanes, ships, etc., not receiving the attention it deserves? The use of a mask, especially by the sick, appropriate ventilation rates, washing of hands regularly, and cleaning of indoor surfaces are necessary for mitigating the spread of contagious virus irrespective of their particle size.

Do you want to know more about this topic? Read Han et al. (2013), Li et al. (2007), Milton et al. (2013), Smieszek et al. (2019), Wei and Li (2017) papers.