Have you ever wondered how to figure out your risk of catching COVID-19 while indoors?

Researchers at the University of Cambridge and Imperial College London have created a COVID-19 risk calculator known as Airborne.cam which can help you work it out by inputting simple data. 

The application is a way for users to discover how mitigation measures affect the indoors transmission of SARS-CoV-2 virus. Inputting data like floor area and ceiling height, length of time in the specific setting, ventilation levels, number of people in the room and other variables will create a percentage chance of being infected over a given time.

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However, it goes into more detail than that, with users able to input the type of mask worn – whether it's FFP2/N95, surgical, 2-ply cloth or 1-ply cloth – in addition to the type of movement in the room, be it or sitting or standing. 

The scientists behind the calculator say it allows people to see how the risk of infection increase or decreases based on certain factors. They do, however, warn that the estimated risk should be treated with caution and is not completely reliable. 

Here are seven examples of how it works, created by CGTN Europe. The different settings demonstrate how being masked or unmasked, ventilation and the space in the room can all play a role in contributing to the risk of catching COVID-19 in a given environment.

Classroom

The first setting is a typical-sized classroom with 30 children and one teacher, with two of those people carrying COVID-19. The calculator suggests that during a typical six-and-a-half hour school day with everyone wearings masks and normal ventilation, the risk of catching COVID-19 by the end of the day is 51.36 percent. 

Metro carriage (London Underground)

Setting two takes a carriage on the London Underground Jubilee Line as a typical example of the risk of catching COVID-19 on the metro. Carrying on average 137 passengers (90 percent wearing masks) with 10 infected on a 25-minute journey which is typically not well ventilated, the calculated risk of catching COVID-19 by the end of the journey is 11.71 percent. 

Supermarket 

Scenario three works out the risk of catching COVID-19 in a supermarket – a place many frequent even during lockdowns and when working from home. The calculator estimates that the risk of catching SARS-CoV-2 in a grocery store of 12,000 square meters is 0.75 percent. 

Of course, this low level of risk is based on the shop being five meters high, well ventilated and all people wearing masks. It is also based on there being a limited number of people in the shop at one time, with just a capacity of 85 shoppers and only eight being infected. Despite this, the length of time in the shop is 45 minutes which means that the risk is still below one percent if all of these factors are taken into consideration for working out the risk. 

Small office 

Setting four, a small poorly-ventilated office shows the stark difference that opting to wear or not wear a mask can make in catching COVID-19. Without a face covering, the risk of catching COVID-19 with 25 people sitting at desks and one person infected is 31.37 percent. On the other hand, wearing a mask across the same 8.5-hour day reduces the chances of catching COVID-19 by almost 10 percent to 21.84 percent. 

Larger office

Setting five shows that the risk of picking up COVID-19 unmasked in a larger office is 23.6 percent with two people infected. When switching around the different valuables in the calculator, the risk of catching the virus significantly decreases when the office workers are wearing masks and when there's more ventilation. 

Average size home

In a typical home, Airborne.cam suggests that the likelihood of catching COVID-19 is very high at 77.41 percent. Varying the number of people in the household did not significantly reduce the risk of catching COVID-19 by the end of the day, but the level of movement around the house i.e. sitting instead of standing and wearing a mask inside the house both reduced the risk of transmission and ultimately catching COVID-19. 

Bus

The final setting, a bus, shows that with very specific variables, the risk of catching COVID-19 is 2 percent – but as claimed by the scientists involved, this risk percentage should be viewed with extreme caution. This low risk percentage is dependent on 15 passengers all wearing masks in addition to the two carrying COVID-19 not wearing a mask. It is also based on all the passengers being seated on a well-ventilated bus. 

As in the other scenarios, the risk significantly jumped when people were not wearing masks, when the environment was less well-ventilated and when people were moving around more rather than sitting down. 

The risk calculator demonstrates that there is no definitive way to determine that the risk of COVID-19 is higher in one setting than another, as the scenarios show that the risk of catching SARS-CoV-2 is complexly intertwined with many different environmental and social factors. 

Graphics editor: Paula Harvey