Corridor, stairwell: how much distance is necessary?

How high is the risk of infection if you keep your distance and walk one behind the other through a narrow corridor? Is the minimum distance of 1.5 meters sufficient?

The required corona safety distance could in certain situations - for example when walking behind one another indoors - strongly depend on the environment. Flow models indicate that it makes a big difference whether a hallway or aisle is narrow or wide, as Chinese researchers write in the journal "Physics of Fluids". In addition, children may be more at risk than adults in such a situation. The researchers did not investigate the actual risk of infection.

Safety distances should be different

Xiaolei Yang from the Chinese Academy of Sciences in Beijing (China) and his team wanted to know how the droplets spread behind a coughing person when they walk down a hallway or hallway. They discovered that the crux of the matter was the width of the corridor. The scientists conclude that it is necessary to recommend different safety distances depending on the environment.

The researchers simulated the spread of a cloud made up of around 1,000 such droplets. The coughing person walks at a brisk pace. Xiaolei Yang and colleagues compared the influence of walls on the side: in one case the walls were six meters apart, in the other case 1.2 meters. In the simulations, the team assumed that the coughing person is not wearing a mask.However, previous studies have shown that wearing a mask can be effective in reducing the risk of spreading infectious droplets.

Aerosols are better distributed in wide corridors

With their models, the researchers found that the cloud of droplets can spread in two fundamentally different ways. In the wide corridor - i.e. at a distance of six meters from the wall - air turbulence behind the coughing person ensures that a good part of the droplets are drawn along with it. As a result, they are distributed relatively well in the room. This could reduce the virus load for a person following behind.

In narrow corridors, i.e. with a wall distance of only 1.2 meters, the turbulence behind the potentially infected person does not have the same effect. To put it simply, the majority of the droplets remain suspended in the air and are less mixed. As a result, there is a cloud with a significantly higher concentration of droplets at a distance of around five meters from the coughing, walking person. "This is a major challenge in determining a safe social distance in places like a very narrow corridor," Xiaolei Yang said in a statement from the Chinese Academy of Sciences.

Children are particularly at risk

In Germany, a distance of at least 1.5 meters to other people is recommended in order to reduce the risk of infection.

The researchers also found that behind a person walking, coughing, the droplets are mainly distributed at waist height - regardless of the width of the corridor. This suggests that children who walk behind an infectious person are at a higher risk of transmission.