When I was grocery shopping recently, the escalator leading up to my car in the parking garage was roped off and out-of-order. There was only one way out: the elevator. I wasn’t a fan of elevators before the pandemic, but now that they’re seemingly giant COVID boxes, I’m even less interested in stepping inside of one.
The thing is, Joseph Allen, a professor of exposure sciences at Harvard University’s T.H. Chan School of Public Health, assures me that elevators aren’t as much of a coronavirus magnet as I might think. “I understand people have anxieties about elevators, but the reality is that the elevator is going to be a low-risk environment,” Allen tells me.
Over the last year, Allen and his colleagues have learned more about how coronavirus spreads, mostly through respiratory droplets that can remain airborne for up to three hours. They’ve also found that the risk of exposure comes down to three key factors:
- Intensity (how much virus a person is shedding)
- Frequency (how often a person goes into a space where virus droplets are present)
- Duration (how long they’re there for)
Most people ride elevators twice a day (if that), and for less than two minutes at a time. As such, the main thing to worry about is intensity of exposure, which can be controlled fairly easily. “Wear a mask, face forward and no talking,” Allen advises. “I’d love to see every elevator with these rules posted in it.”
The no-talking rule is especially important because, much like singing, small talk produces more airborne particles than silence. At last then, we can stop making chitchat in the name of public health. “I imagine a lot of people might like that anyway,” Allen laughs.
That said, Richard L. Corsi, dean of engineering and computer science at Portland State University who studies air quality, created a model based on existing information about the virus and elevator mechanics to hypothetically predict elevator safety conditions. He found that if someone rides alone for 31 seconds without a mask, coughs and talks on a cell phone, then exits, approximately 25 percent of their viral particles will still be there for the next passenger, even after the doors open and close twice.
“The main intent of the exercise was just to show that some level of virus can be sustained in air beyond an infected person using the elevator,” Corsi told the New York Times. “I don’t know whether the dose in an elevator is going to be high enough to pose significant risk, but I would probably take the stairs if possible.” Linsey Marr, an aerosol scientist at Virginia Tech, also argues that there’s too much variability between buildings to be sure and that “it really depends on the elevator.”
However, Allen, who’s studied building ventilation and co-authored the book Healthy Buildings: How Indoor Spaces Drive Performance and Productivity, maintains that “it doesn’t matter if it’s an old building or new building — elevators are low risk” if, he reiterates, everyone wears a mask. To that end, long before COVID, elevators were made to accommodate a high density of people, and had to be properly ventilated by design. If they weren’t, we’d have much stuffier, hotter and uncomfortable experiences inside of them.
The bigger concern to Allen is that all the precautions being taken to limit elevator occupancy to one or two people per ride may hurt more than they help. “The intent is to reduce risk in an elevator, but it may inadvertently cause a higher risk, as you force people to stand in lines and wait,” he explains. “When you have a lobby of people waiting for a long time, the duration is longer, at a higher occupancy density.”
As for whether or not taking the stairs is safer given the option, Allen considers the level of risk about the same. People tend to breathe heavier while taking the stairs, potentially blowing out more particles, even if they have the ability to distance. Thus, the two risk indicators balance each other out, again, provided everyone is wearing a mask. “It’s critically important that you wear a mask,” Allen stresses.
Otherwise there’s no difference between the stairs and an elevator, save for what it does to your butt.