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MIT Tool Models COVID-19 Exposure Risks in Different Settings

An app developed by professors at the Massachusetts Institute of Technology uses a theoretical model to calculate safe exposure times to the virus and safe occupancy levels for a variety of indoor spaces.

by Annalise Knudson, Staten Island Advance / December 2, 2020
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(TNS) — Throughout the ongoing coronavirus (COVID-19) pandemic, public health officials have reminded us time again that outdoor spaces are safer than indoor spots, and that more people in one space poses a greater risk, and social distancing and mask-wearing are necessary.

But a new online tool can help you find out just how likely you are to catch the coronavirus if you are exposed to an infected person in different scenarios, like in your home, school, or office.

The tool was created as growing scientific evidence shows that COVID-19 is mainly spreading in homes and other indoor spaces whenever people spend extended periods breathing tiny infected aerosol droplets suspended in the air. And while public health officials acknowledge airborne transmission, there is no safety guideline that incorporates all the relevant variables.

The app, developed by Kasim Khan in collaboration with Martin Z. Bazant and John W. M. Bush, professors at the Massachusetts Institute of Technology (MIT), uses a theoretical model to calculate safe exposure times and occupancy levels for indoor spaces.

It adjusts room specifications, ventilation and filtration rates, mask usage, respiratory activities, and risk tolerance, to see how to mitigate indoor coronavirus transmission in a variety of indoor spaces — and that's only if one person is infected in that space.

More people in an indoor space shortens the amount of time you are safe from contracting COVID-19.

For example, 25 people are safer in a large gymnasium rather than in a crowded bar, and six feet of separation is safer in a ventilated hospital than inside a sealed tent. And social distancing can be safely reduced so long as face masks are worn properly, covering both the mouth and nose.

Consider a standard 20-by-20-foot room in your home, with 10 people over for dinner. Guests are not wearing a mask because they are eating. The windows are closed because it's cold out, and there is regular, residential ventilation. People are talking while they are eating dinner. According to the tool, it's safe for 10 people to be in that room with one infected person for 37 minutes before they are considered at risk of contracting the virus.

If people social distance and wear a mask in any room, groups of people can hang out indefinitely — but that is nearly impossible for most situations.

But wearing a mask, increasing ventilation, and taking other safety measures can increase the time you are safe in the same room with 10 people. If you wear a coarse cotton mask, that only increases your time by four minutes. Opening windows brings your total time up to 63 minutes.

Wearing a surgical mask will keep you safe with 10 people for three hours.

Another example shows the risk of being in a New York City subway car if one person is infected with COVID-19 — where people are standing, typically talking in a lower voice or whisper, assuming they wear a mask properly, with average humidity. Under these circumstances, the tool shows it is safe for 25 people to be in the subway car for 15 hours.

A standard classroom lecture room with similar humidity, mask usage and ventilation can hold 35 people safely for seven hours, according to the tool.

In a restaurant, where people are wearing a mask while eating and talking, the tool says it's safe for 50 people to be in the indoor space for two hours if one person is infected.

You can use the model here to see the risks associated with different indoor spaces, depending on ventilation, mask usage, and more. Remember that the model is a simulation, and only measures risk of contracting the coronavirus if one infected person is in the space.

And more vulnerable populations, like people 65 and older, or those with pre-existing conditions, are more at risk of contracting the coronavirus in these indoor spaces, according to the tool.

The tool makes one thing certain.

As the weather gets colder and more people move into indoor spaces, make sure you wear a mask, social distance, and don't converse with large groups of people for the best protection against the coronavirus.

©2020 Staten Island Advance, Distributed by Tribune Content Agency, LLC.

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