For people in cities like New York, getting back to work during a pandemic may mean taking several elevator rides a day, to and from their office spaces — but without safety measures in place, elevators could become hot spots of COVID-19 spread, data suggests.
COVID-19 can spread when infected people cough and spew large respiratory droplets, either contaminating people directly or depositing the virus onto nearby surfaces. The virus can also spread through smaller particles called aerosols, expelled when people breathe, talk or sing. Several superspreader events, where many people caught the virus from one infected individual, suggest that crowded, indoor spaces with poor ventilation present huge risks for disease transmission; elevators, being enclosed metal boxes with frequently-touched buttons, carry similar risks for spread, The New York Times reported.
This week, the U.S. Centers for Disease Control and Prevention (CDC) plans to release official guidance for how to ride elevators safely while the coronavirus still circulates, according to the Times. The recommended measures will include: requiring all riders to wear masks; limiting the number of riders; marking paths on the floor to direct people in and out; and posting signs to remind people to "not talk unless you have to," Nancy Clark Burton, a senior industrial hygienist at the CDC, told the Times.
"They should put big signs on the elevator: 'Do Not Speak,'" Richard Corsi, dean of engineering and computer science at Portland State University and a specialist in indoor air quality, told the Times. In April, Corsi developed a computer model to simulate how an infected person might contaminate an elevator while riding between 10 floors, and how much virus might remain in the elevator after the rider exits. He shared the results on Twitter, and discussed the research in a related New York Times report, published in May.
"Admittedly high uncertainty here, but this single hypothetical scenario does suggest that elevator cabin air may remain infectious for trips beyond infector exit," he wrote in a tweet.
Factoring in standard elevator speeds, ventilation systems and door closing times, the model simulated how much virus would be expelled from an unmasked person who coughed and spoke on a cell phone during the ride. A single cough can expel several thousand to several hundred thousand viral particles, for context, Corsi told the Times. He estimated that speaking on the phone would expel about one-fiftieth the number of viral particles per second compared with a light cough, although that number may vary widely in real life, he noted in a tweet.
Once contaminated, air within the elevator mixes with air outside as the elevator doors open and shut, and the infected passenger steps out. The model estimated that when a second passenger steps into the elevator, they would be exposed to about about 25% of the viral particles expelled by the infected rider.
This percentage would vary depending on the elevator and air pressure within a given building, and regardless, the lingering viral particles may not be plentiful enough to actually infect the second rider, Corsi cautioned. Scientists haven't determined how many viral particles a person must inhale to become infected, so the likelihood of catching COVID-19 from viral bits floating in an elevator cannot be precisely calculated, he noted. "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 said. "I don't know whether the dose in an elevator is going to be high enough to pose significant risk."
While the risk of riding an elevator after an infected person has exited remains unclear, riding with an infected person definitely poses a significant risk of transmission, especially compared with spending time near that person in a less confined space, Corsi said. "Standing as far away as you can diagonally in [the] elevator would be good, and do not speak," he said.
In most states, the standard elevator must be at least 4 feet 3 inches deep and 5 feet 8 inches inches wide (130 centimeters by 173 cm), according to the Stanley Elevator Company, The New York Times reported. These dimensions make maintaining distance between yourself and others very difficult. "I can't give you the six feet in an elevator — you'd have to have someone on the ceiling and someone on the floor," Andrew Hardy, head of operations at JEMB Realty, a privately held company that owns and operates residential and commercial properties, told The New York Times.
A new high-rise being built by JEMB Realty in New York will include touchless elevator technology, which allows riders to call their elevator using a key card or fob, Hardy noted. In addition to touchless technology, new elevators could include improved air ventilation, antimicrobial materials and the use of ultraviolet light to disinfect surfaces, Lee Gray, an elevator historian from the University of North Carolina at Charlotte and correspondent for Elevator World Magazine, told the Times.
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Originally published on Live Science.
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Nicoletta Lanese is the health channel editor at Live Science and was previously a news editor and staff writer at the site. She holds a graduate certificate in science communication from UC Santa Cruz and degrees in neuroscience and dance from the University of Florida. Her work has appeared in The Scientist, Science News, the Mercury News, Mongabay and Stanford Medicine Magazine, among other outlets. Based in NYC, she also remains heavily involved in dance and performs in local choreographers' work.