Animation shows how opening a window can drastically stem coronavirus circulation in classrooms, as schools prepare to resume in-person learning

• Studies increasingly suggest that schools can safely reopen if the right precautions are followed.
• The NYT published an animation showing how virus particles can move around a classroom if one student is infected.
• Air circulation in the room is important to keep spaces safe for students and teachers.

As some US schools start resuming in-person learning, an animation shows why it is important for classrooms to have good air ventilation.

The graphics, which were designed by the New York Times in collaboration with experts, simulates the flow of the coronavirus in a typical New York City public-school classroom in different scenarios with increasingly improved ventilation.

In this example, the windows are closed. Even with social distancing and mask wearing, the animation shows how the students' breath still circulates in the classroom:

In this case, around 3% of the air that each person breathes was exhaled by someone else, The New York Times said.

The Times then modeled what would happen if there is an infected student in the classroom.

If there isn't fresh air in the room, the breath of the infected student accumulates in the room, as this graphic shows:

In this situation, the concentration of the virus in the air is high, as is shown by the dark red color of the lines in the graphic above.

Though it is not clear what how much exposure to the virus is needed to infect someone yet, "exposure is a function of concentration and time," one of the experts who worked on the animation, Joseph Allen, told The Times.

As such, it seems logical that the more the virus is concentrated in the air and the longer people who aren't infected are exposed to the virus, the more likely they ultimately become infected.

But if a window is opened, it is a different story. The virus continues to circulate, but doesn't accumulate as much:

The Times then showed what would happen if air was blown into the classroom using a fan and a high-efficiency particulate (HEPA) filter.

The results were better, as seen below, as the fan helped spread the particles in the space:

The experts suggested that the best combination is to have an air purifier in the room as well as a fan to blow the air out of the room.

Having the fan draw the air out of the room, rather than in, means that the air is sucked away from an infected person, rather than blown from the infected person toward someone who is not infected.

The Times' animation comes as studies increasingly suggest that schools should be safe to resume in-person learning, if the right precautions - like social distancing and mask wearing - are followed.

Children don't seem to get as sick from COVID-19 as adults. According to the Centers of Disease and Control and Prevention, fewer than 250 children have died from COVID-19 in the US, compared to more than 500,000 deaths in total.

Some New York City middle schools reopened for the first time since the pandemic last Thursday, with 62,000 students from the sixth to eighth grades restarting a mixture of in-person and remote learning, NBC New York reported.

Under the city's strict return-to-school rules, students are expected to sit at desks six feet apart and wear cloth masks to class, The Times reported. The city also mandates that at least one window be open in classrooms, The Times said.

The CDC also published guidance last month urging K-12 schools to reopen. An in-person learning option is currently required in Iowa, Arkansas, Texas, and Florida, according to CNN.

President Joe Biden has said that he expects K-8 schools to be open five days a week within his first 100 days in office.

However, many US schools districts don't have the funding to improve the ventilation in their school rooms, as Insider's Aria Bendix reported. A survey conducted last June found that 41% of school districts need to improve their ventilation systems.

Resistance to mask wearing in schools could also prove tricky to their reopening.

In Georgia and Iowa, where schools have already resumed, there aren't strict mask-wearing policies in place.

One CDC investigation in Cobb County, Georgia, between December 1, 2020, and January 22, 2021, suggested that two infection clusters started with teacher-to-teacher interactions. Inadequate masking and social distancing might also have been a factor, the researchers said.