Active Ventilation Can Curb Indoor Coronavirus Spread, Says Engineer

Critical to curbing the spread of the coronavirus indoors is maintaining a high air exchange rate.
Brad Bergan

A professor of mechanical engineering from the University of Colorado Boulder wrote a guide on Science Alert advising everyone to keep their living space well-ventilated because it lowers the chance of contracting the coronavirus associated with the COVID-19 illness.


Well-ventilated indoor spaces are crucial to avoid coronavirus transmission

Most coronavirus transmission happens inside — typically from the inhalation of airborne particles saturated with coronavirus particles.

The best way to stop the virus from spreading throughout homes and businesses is keeping infected people out, but since roughly 40% of cases are asymptomatic — and also contagious — another solution is needed, said Shelly Miller, author of the guide published on Science Alert.

While masks are a great way to slow the spread of the virus into the surrounding air, they still let some infected air particles out into the surrounding environment. And if this is a contained space, those coronavirus particles aren't going anywhere.

Once the virus is freely moving inside an indoor space, said Miller, there are two options: we can let in fresh air from outside, or remove the virus from the indoor air.

Fresher, outdoor air is better than stale, closed rooms

The safest way to remain indoors is one with a constant flow of outside air pouring into and replacing the indoor air, said Miller. Commercial buildings usually pump outside air into themselves via heating, venting, and air-conditioning (HVAC) systems.

In private homes, outside air pours in through doors and open windows, while also seeping through the cracks, nooks, and crannies throughout the structure.

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In other words, maintaining a fresher, outdoor-air environment is better than living in a stale, indoor petri-dish of a house. When we bring in fresh air, it dilutes the concentration of infected particles in any given space, whether it carries the coronavirus associated with the COVID-19 illness, or any other virus.

Maintaining high air exchange rates

Miller is also an environmental engineer, who are a group of people often asked to quantify how much outside air makes it into a building using a rate of measure called the air exchange rate. This is a number that quantifies the number of times indoor air is replaced with outside air in one hour.

The exact rate depends on the number of occupants and size of the indoor space, but most experts agree roughly six air changes per hour is sufficient for a 10-ft-by-10-ft space housing three to four people.

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Amid a pandemic this rate should be higher, says Miller. A 2016 study suggests that an exchange rate of nine times per hour can substantially reduce the spread of MERS, H1N1, and SARS in a Hong Kong hospital.

Obviously, many buildings in the U.S. — like public schools — don't come close to meeting these guidelines for optimal air exchange rates. But as they and many other buildings across the country begin to refill with students, workers, or whoever — we should remember to mind the staleness of the air amid the ongoing coronavirus crisis.

We have created an interactive page to demonstrate engineers’ noble efforts against COVID-19 across the world. If you are working on a new technology or producing any equipment in the fight against COVID-19, please send your project to us to be featured.

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