For people living or working in high-rise buildings, using an elevator becomes riskier due to coronavirus infection. Tut.by tells what scientists know about this, and what precautions they recommend.
“It’s difficult to answer this question unequivocally,” admits Lyncy Marr, an aerosol specialist at Virginia Tech. “Much really depends on the elevator.”
Most lifts are not large enough for people to keep a distance of 1,5–2 m from each other, so it is likely that infected passengers can transmit the virus to others, especially if they don’t wear a mask and cough, talk or even breathe hard because they are out of breath .
But even if you ride the elevator alone, there are other ways to get coronavirus, although the risk is less. Buttons in the cockpit pose a potential hazard if you touch them, and then your face. Or air. If you entered the elevator after an infected person rode in it, are microbes hovering in the cab?
Richard Corsi, an indoor air quality specialist at Portland State University, decided to learn more about elevator safety by creating a model using the principles of engineering and fluid mechanics. But given the variety of elevators and buildings, there are thousands of scenarios that give different results.
What size is the elevator? How fast does an elevator pass between floors? How long do the doors remain open, allowing fresh air to enter the cabin before the doors close again? Does the elevator have a ventilation system?
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Dr. Corsi decided to simulate a hypothetical elevator ride using the average parameters of cab speed, door closing time and ventilation system. In this model, infected passenger A enters the elevator on the ground floor and travels alone for 31 seconds to the 10th floor of a residential building. During the trip, a passenger who is not wearing a mask coughs and talks on his cell phone, exhaling tiny droplets containing the virus. Some drops fall to the ground, some hit the elevator walls, some float in the air.
The elevator stops on the 10th floor. Doors open for 10 seconds when the passenger exits. He takes with him a certain fraction of the microbes due to swirling and mixing of air, diluting the air contents of the elevator by about half. The doors close and the elevator goes straight to the second floor, where passenger B is waiting for him. Doors open, air in the elevator circulates again, a healthy passenger enters.
Based on this model, passenger B is exposed to approximately 25% of the viral particles that passenger A left during his trip. Dr. Corsi recalls that the amount varies in different elevators.
A more serious question is whether passenger B will become infected due to exposure to viral particles during a short trip in the elevator. In the process of coughing, a person can emit several thousand or even 300 thousand particles, and doctors still do not know what dose of coronavirus - one virus particle or thousands - makes a person sick.
“The main goal of my experiment was to simply show: a certain level of the virus remains in the air of the elevator after an infected person,” Dr. Corsi said. “But I don't know if the dose will be high enough to pose a significant risk.” If possible, I myself would climb the stairs. "
However, many infectious disease experts do not believe that airborne particles in empty elevators pose a significant risk in real life when it comes to coronavirus. Dr. Ilan Schwartz, assistant professor of infectious diseases at the University of Alberta, noted that even when a person with COVID-19 lives in close proximity with other family members, the incidence rate is estimated at about 10–20%.
Although it is possible that drops with a coronavirus can soar in the air for some time, in the real world the main mode of transmission is the direct effect of an infected person: for example, a cough in your presence.
“We know that there are small particles that can remain in the air, but in the end, epidemiologists simply do not confirm that this is an important way to transmit the disease,” said Dr. Schwartz. “Probably, the risk of being in the elevator will be more associated with touching the buttons than with touching the air that the one who used to ride in it exhaled.”
The solution for those who cannot do without an elevator is to take precautions. First, if possible, avoid taking the elevator with another person. Secondly, it makes sense to put on a mask, even if you are alone in it - this will help protect you from the last passenger and protect the next passenger from your germs. Do not touch your face after touching the elevator buttons, and wash your hands as soon as possible.
Dr. Marr notes that the presence of viral particles in the air does not necessarily mean that a person will get sick, but you should still take measures to avoid the risk. “Viral RNA tells us that the virus exists, but does not indicate whether it can infect,” she said. - If we find 100 copies of viral RNA, we assume that we can talk about one infectious virus. It is not known how much it takes to get sick, but more than one is more likely. The risk is low. But I'll put on a mask in the elevator. ”