New Delhi: AIIMS Director Randeep Guleria has recommended certain precautions against the aerosol and droplet spread of COVID-19 in closed indoor spaces. These include:
1. Good cross ventilation with exhaust and air exchange
2. Good air exchangers for fresh air in case of AC
3. Installation of high-efficiency particulate air (HEPA) filters in ACs or air purifiers.
The World Health Organization (WHO) had recently acknowledged that COVID-19 is airborne and can spread as aerosol or droplets.
In a YouTube video, Dr Mike Hansen, a pulmonologist from USA, explained how the virus can travel as aerosol for distances greater than six feet and up to 27 feet in some cases.
He said the smallest particle emitted from our mouths could be less than one micron (um) and the biggest is over 500 um in diameter. The human hair is around 80 um. Droplets smaller than 5 um are a concern and these can stay suspended in air, he said. The larger droplets settle down due to gravity, typically within 6 feet and hence the social distancing recommendation.
The tiny particles, however, act more like a gas cloud, where they float in the air, and travel up to 27 feet, Hansen pointed out referring to a study carried earlier.
These tiny droplets evaporate within milliseconds of hitting the air depending on temperature, humidity and other factors. What’s left behind is the virus floating in the air. These are known as droplet nuclei or aerosols, Hansen said.
These droplet nuclei have been found to stay airborne for about 3 hours, according to a study by National Institutes of Health.
Hansen, however, said that there’s no 100 per cent conclusive evidence on airborne transmission, but there’s enough to suggest it.
He also recommended using HEPA filter air purifiers to reduce the spread of virus indoors.
Major airlines such as Emirates have started fitting HEPA filters in their aircraft to reduce the virus spread.