University of Cambridge online tool shows how ventilation reduces risk of transmission of Covid-19 in classrooms


With students returning to classrooms starting March 8, a new tool created by researchers at the University of Cambridge could help show schools how to reduce the risk of infections in classrooms.

Scientists built the tool to show the impact of wearing masks, opening windows, and more downtime on reducing the amount of Covid-19 virus in the air.

Distancing, masks and ventilation can reduce transmission of Covid-19

The results, published in the journal Proceedings of the Royal Society A, show that social distancing measures alone do not provide adequate protection against the virus.

Researchers, from the University of Cambridge and Imperial College London, used mathematical models to show how SARS-CoV-2 – the virus that causes Covid-19 – spreads in different indoor spaces depending on the size, occupancy, ventilation and the presence or absence of masks. being worn.

These models are also the basis of a free online tool,, which helps users understand how ventilation and other measures affect the risk of indoor transmission and how that risk evolves over time. time.

The scientific consensus is that the vast majority of Covid-19 cases are spread by transmission indoors. With schools returning next week, the tool could help school leaders determine exactly what risks children and teachers face and what they can do to make classrooms safer.

Dr Pedro de Oliveira, Cambridge Engineering Department, and first author of the article, said: “In a school environment, to be safe, you need to make sure that the rooms are not overcrowded and that you have sufficient ventilation and that children are a different safety distance from each other.

Opening windows could help reduce the spread of Covid-19 at school
Opening windows could help reduce the spread of Covid-19 at school

“By using our tool, you can understand, in addition to following government regulations, how you can improve your indoor conditions. You can see the effect that different qualities of mask will have on the risk of infection and the relative reduction in risk that you can do with ventilation and occupancy.

“You can see what the effect will be if you increase the ventilation rate and take breaks throughout the day when no one is in the room, it can also impact the risk of infection. . “

The tool allows users to enter the size of the room, the number of people inside, the type of mask they wear, the amount of fresh air coming in, and how long the room will be empty during the daytime. For these responses, it provides a percentage risk of catching the virus from an infected person in the room. Dr Oliviera said the university was already using this tool to assess whether conference spaces and seminar rooms were sufficiently ventilated.

The latest government directive is that all high school students, except those with an exemption, should wear masks in classrooms if they cannot be more than two meters from the next student.

However, Claire Coates, principal of Cambourne Village College, said: “The biggest misconception – students are not socially distanced in the classroom. They are tighter than usual because there must be a two-meter safety zone in front of the classroom behind which the teacher is standing. If you have a typical 55 square meter square classroom with 32 children, these rows are set back to give that extra space up front so the children are actually closer to each other in the classroom than they are. ‘would have been. And two of them are seated at a table, shoulder to shoulder.

She said it would be easier to keep students at a safer distance if schools returned on a rotating system.

“If the schools had had some kind of flexibility, we could have increased social distance at school. But that’s not the case and it also puts a lot of pressure on schools to make individual decisions and potentially makes logistics even more difficult.

College students will have to wear masks
College students will have to wear masks

Another school trust is concerned about how students will be kept in their bubbles during lunch hour.

Stephen Munday, Managing Director of CAM Academy Trust, said: “What are you doing with social spaces? How do you serve lunch? Where are they going? In our high schools and depending on the weather, we’ll see if we need to rent marquees, which we used to do, to create more spaces so that groups can have a place to go outside of class where they can socialize in. their bubbles and with protocols in place. “

The trust seeks to have meals delivered to specific areas of the school to limit travel or to create ready-to-go meals that students can pick up and take to a designated eating area.

Cambridgeshire County Council Education Director Jonathan Lewis said he had given ventilation advice to schools: ‘What we are getting into here is exactly the same that we have been involved in in September. The outbreak of Covid cases at school has been very small compared to the number of people we have there.

“There are risk assessments, there is advice and guidance – we have given information on ventilation, cleaning, and so on.

See the tool on

Additional reports: Gemma Gardner

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