When are HEPA filters necessary and when would more affordable filters suffice?

What is it about?

The risk of transmission of airborne viruses is increased in indoor settings, but how big of a difference can AC filters actually make? When are HEPA filters necessary and when would more affordable filters suffice? Our study looks at the fluid mechanics of how potentially virus-laden airborne nuclei can reach a host. We distinguish between a direct route in which the virus-carrying nuclei travel directly from the infected person to a receiving host and an indirect route, in which the nuclei are removed from the room and go through the ventilation system only to be re-injected back through the ventilation inlets.

Featured Image

Photo by Maxime on Unsplash

Photo by Maxime on Unsplash

Why is it important?

A high quality filter will limit the amount of nuclei that re-enter the room. In fact, nuclei can recycle many times through the ventilation system before finally reaching the receiving host. What sets our study aside from others is that we use a process known as statistical overloading to provide statistically relevant results by accounting for practically all possible direct and indirect routes, taking into account the turbulent chaotic nature of indoor air. This process is computationally expensive compared to traditional simulations and necessitates the use of tens of millions of droplet nuclei which are individually tracked for up to one or two hours. Our approach can handle any type of filtration and provides a correction function that can be easily used in conjunction with simple models to improve the fluid mechanics aspect of tracking droplet nuclei and provide an improved estimate for the risk of infection. Our easy-to-implement correction function accounts for the separation distance between the sick and the susceptible individuals, an important feature that is difficult to statistically quantify due to the turbulent chaotic nature of indoor air.

Perspectives