Walking down a narrow corridor may increase the risk of getting Covid-19 as viral droplets linger in the air up to 16 feet behind an infected person
- The researchers used computer models to see how space changes airflow
- Found narrow walls like in a corridor change the behavior of particles through coughing
- In the open space, they snap into place on the back of the puma and form a “tail”.
- But in a corridor, they loosen up, forming a ball of floating particles that are several feet behind the person and can last several seconds
Coronavirus particles ejected from a person’s uncovered mouth in a confined space like a corridor can linger at waist height behind them for a few seconds, a study warns.
The result comes from computer simulations showing how particles behave after they have been coughed up by someone walking forward.
Swirling air and eddies cause the particles to float in the air up to five meters behind the infected person, creating significant problems for social distancing and the risk of infection for children.
Left image: The freestanding mode created in a narrow corridor where a highly concentrated mass of suspended coronavirus particles can be seen several feet behind an individual. Right: The same person walking at the same speed but in an open corridor. It shows an “attached” form of circulation where particles stick to the person’s back and shoot out like a waist-high tail
As an example, researchers at the Chinese Academy of Sciences in Beijing used a 1.8 m (5 ft 11 in) man walking at 1.5 m / s (3.5 miles per hour).
They modeled what would happen if he coughed without a face mask both in wide open spaces and in a narrow corridor.
Previous studies have focused almost exclusively on the spread of infectious particles in places with no restrictions. This new study examined how the behavior of particles differs when they are physically written.
They found that airborne droplets carrying the deadly virus follow a pattern called “detached mode” when walking in a confined space.
Computer visualizations show that particles are thrown behind a person by the air currents created when walking. A cloud of droplets separates from the body and forms a floating clump of infectious aerosols several feet behind the individual.
This graph shows what happens when a 5-foot-11-inch man walks at 1.5 m / s and coughs in a corridor (left) and in an open space (right). In the latter, the particles are bound to the back of the individual, and in the former they form a separate sphere several meters behind
It is highly concentrated and arises as a direct result of the walls buffing and directing air in one direction.
In an open room, however, the researchers found out that virus-laden droplets take a different course from a cough.
When air flows over a person’s shoulders and back, it also flows around their waist and back, with both flows meeting in the middle.
As a result, the particles produced by coughing in an open space become entangled in a “recirculation bubble”.
The majority of the particles sit here, but some also emerge from behind the person as they walk, forming a long, thin, and invisible tail of coronavirus particles.
The researchers say this so-called “attached mode” puts children at a particularly high risk of contracting the virus in this way because it is at an adult’s waist height but a child’s head height.
Professor Xiaolei Yang, author of the study, added, “The results show, in some cases, a higher risk of transmission for children, for example behind fast-moving people in a long, narrow hallway.”
‘In detached mode, the droplet concentration five seconds after a cough is much higher than in attached mode.
“This is a major challenge in determining a safe social distance in places like a very narrow corridor where a person can inhale viral droplets even if the patient is far in front of them.”
The results were published in the journal Physics of Fluids.