Engineers say, where you sit in a room, your risk of catching COVID-19 may be affected.


It does not take long for the aerial coronavirus virus to make its way through a room. First, only those sitting near an infected speaker are at high risk, but small aerosols can spread as soon as the meeting or class is underway.

However this does not mean that everyone faces the same level of risk.

As an engineer, I am conducting experiments on how aerosols move, including the size ranges that can carry viruses.

What I have found is important to understand as more people return to universities, offices and restaurants and more meetings are held indoors as temperatures drop. This points to the highest risk areas in rooms and why proper ventilation is important.

As we saw with President Donald Trump and others in Washington over the past few weeks, coronovirus can spread quickly to nearby quarters if caution is not taken.

University campuses are also battling COVID-19. The number of children between 18- to 22-year-olds in the Midwest and Northeast doubled after schools reopened in August.

As the case progresses, the danger increases for those who spend time in those rooms.

An experiment shows who is at greatest risk

Most current models describing the role of ventilation on the fate of airborne microbes in a room assume that the air is well mixed, in which the particle concentration is uniform.

In poorly ventilated rooms or small spaces, this is true. In those scenarios, the entire room is a high-risk area.

However, in larger locations, such as in classrooms, good ventilation reduces the risk, but possibly not uniformly. My research suggests that how high the level of risk is depends on ventilation.

To understand how coronovirus can spread, we injected aerosol particles similar in size to a room from humans and then monitored them with sensors.

We used the 30-foot by 26-foot university classroom, designed to accommodate 30 students with a ventilation system that met the recommended standards.

When we released the particles in front of the class, they reached the back of the room within 10 to 15 minutes.

However, due to the active ventilation in the room, the concentration at about 20 feet (6.1 m) backward from the source, was one-tenth of the concentration close to the source.

This suggests that with appropriate ventilation, the highest risk for acquiring COVID-19 may be limited to a small number of people near the infected speaker.

As time increases indoors with an infected speaker, however, the risk extends to the entire room, even if the ventilation is good.

CDC finally accepts aerosol risk

In the past, transmission of respiratory diseases has focused on the role of larger particles that are produced when sneezing and coughing occur.

These drops fall to the ground quickly, and social disturbances and infection can be avoided to a large extent by wearing masks.

The major concern now is the role of small particles known as aerosols that we talk, sing or even just breathe. These particles, often smaller than 5 micrometers, can escape with a cloth mask and air in the air for about 12 hours.

The Centers for Disease Control and Prevention eventually acknowledged that on October 5, many others at or close to administration and tested positive for COVID-19 after Trump’s hospitalization.

While these small particles carry, on average, fewer viruses than larger particles, which are released when people cough or sneeze, the high infectivity of SARS-CoV-2 combined with a high viral load before symptoms appear makes these particles airborne. Makes it important for disease transmission.

How much ventilation is sufficient?

To reduce COVID-19 transmission indoors, the CDC’s top recommendation is to eliminate the source of infection. Distance education has done this effectively on many campuses. For face-to-face teaching, engineering measures such as ventilation, partition shields and filtration units can remove particles directly from the air.

Of all engineering controls, ventilation is possibly the most effective tool for reducing infection outbreaks.

Understanding how ventilation reduces your risk starts with COVID-19 air exchange rates. One air exchange per hour means that the air supplied to the room in one hour is equal to the amount of air in the room.

Air handling rates range from less than one for homes to 15–25 for hospital operating rooms.

For classes, the current rules of primary airflow correspond to an air exchange of about six per hour. This means that every 10 minutes, the amount of air brought into the room is equal to the volume of the room.

How high the concentration is based on the number of people in the room, how much they emit and the air exchange rate.

Due to social differences the class population halved and everyone wore masks, in many indoor places the air was actually now before the epidemic compared to the cleaner.

Parts of the room to escape

It is important to remember that not all parts of a room are at equal risk.

There will probably be less air exchange in the corners of the room – so the particles can stay there longer.

Being close to the air exit vent may mean airborne particles from the rest of the room can be washed over you.

A study of ventilation airflow in a restaurant in China revealed its role in several COVID-19 diseases among its patrons.

About 95 percent of the particles in the room will be removed by a properly functioning ventilation system in 30 minutes, but an infected person in the room means that those particles are also continuously emitted.

Particle removal speed can be accelerated by increasing the air exchange rate or by adding other engineering controls such as filtration units. Opening windows will often also increase the effective air exchange rate.

As schools, restaurants, malls and other communal spaces begin to accommodate more people indoors, understanding the risks and following the CDC’s recommendations can help reduce infection.

This story has been updated with the CDC’s newly released guidance on aerosols.chit chat

Suresh Dhaniyala, Bayard D. Clarkson distinguished mechanical and aeronautical engineering, Clarkson University by Prof.

This article is republished from Conversation under a Creative Commons license. Read the original article.

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