The same is true for people infected with the novel coronavirus. When scientists first began studying COVID-19 transmission, they focused on the large, virus-laden droplets produced when those individuals cough, sneeze, or talk. To reduce exposure, the researchers have been urging everyone to stay six feet apart from each other — to social distance. But in a way, that’s like focusing on the ashes of a cigarette while overlooking the spreading tendrils of smoke. In the case of the coronavirus, the tendrils are viral particles that waft in the air. In recent months, scientists have been paying increasing attention to the risk posed by these particles, called aerosols. They’ve also been investigating how proper ventilation — the intentional introduction of fresh air into a space while stale air is removed — may dissipate aerosols indoors and reduce COVID-19 risk. As lockdowns lift and Americans head back to office buildings and schools, understanding the role of ventilation becomes even more critical in the fight against COVID-19. The good news: Experts believe that something as simple as opening a window can make a difference. RELATED: Life After Lockdown: COVID-19 Safety Tips for Offices, Restaurants, and Hair Salons Dr. Dhanak coauthored a study published in June 2020 in Physics of Fluids that found that some viral particles travel as far as nine feet in under a minute. Even singing, breathing heavily, or talking can send these aerosols flying, he says. This is why he and other experts recommend a social distance of more than six feet, when possible. In July the World Health Organization publicly recognized airborne transmission via aerosols as a possible means of novel coronavirus spread, especially in indoor settings. Researchers continue to study how these aerosols behave. In a study posted in August on the preprint server medRxiv, which has not yet been peer reviewed, aerosols containing the coronavirus were found 15 feet from hospitalized patients’ beds. Another study, published in July 2020 in Emerging Infectious Diseases, documented how diners inside a restaurant in China where an asymptomatic carrier ate contracted the virus even though they were sitting at separate tables — the result of aerosol spread. How long an aerosol hangs around depends on the size of each particle. A particle of 5 microns, the typical maximum to be considered an aerosol, will drop roughly two feet in a half hour. But a particle half that size can take four hours, Dhanak says. That’s why you can’t assume you’re safe in a room that is currently unoccupied, since viral particles produced by people who were there earlier might remain. RELATED: Why 10 Feet May Be Better Than 6 Feet
Your Best Defense: Open a Window
To remove virus aerosols, it’s helpful to speed up the rate at which fresh air enters a room and stale air exits, a process known as air exchange. The easiest way to do that is to open a window or door. “When you’re in a room over a period of time, aerosols can collect and hang around. But if you open the windows or doors, you can replace that air with fresh air,” Dhanak says. Creating openings on two sides of a room, to create a cross-breeze, is the most beneficial, he adds. For ventilation purposes, older homes actually have an advantage over energy-efficient new buildings because they aren’t sealed as tightly, notes Shelly Miller, PhD, a professor of mechanical engineering at the University of Colorado Boulder in Colorado, in a question and answer session on the school’s website. This matters because fresh air can leak in through all the cracks in an older house while stale air can exit the same way. RELATED: Legionnaire’s Disease Risk Grows as Coronavirus Lockdowns Lift
Look to Your AC
Opening a window may not always be possible or practical. That’s why you also need to turn your attention to your air-conditioning unit. First, pay attention to how the air conditioner blows and try to position yourself upwind. “If you’re downwind of the flow, there’s a good chance you will see a lot of aerosol material,” Dhanak says, although he notes virus can also congregate in other “dead spots” in the room. Also consider the AC unit itself. Unfortunately, many of today’s highly efficient models “quietly cool and dehumidify room air but provide no outdoor air exchange,” a group of experts noted in an editorial published in February 2020 in the journal Indoor Air. Some large commercial office buildings have systems that can be adjusted to take in more air from the outdoors, noted a July article in the Atlantic. If you’ve been called into work or school, it pays to inquire if this can be done. For your home unit, you might look into upgrading the filter. The trade organization ASHRAE recommends using filters rated “MERV 13” or higher. Dhanak also points to HEPA filters as especially efficient options, although not all AC systems can accommodate these. Companies are investigating whether installing ultraviolet light inside the units might remove even more of the virus, so this might be an option in the future. Another approach to improving air quality may be to use a stand-alone air purifier with a HEPA filter, Dhanak says, although he adds that this type of device has not been researched specifically for the coronavirus. RELATED: Food Safety and COVID-19: A Guide for Handling Groceries and Takeout
Wear a Mask
“It’s important to focus on the filters in your home or office, but don’t forget that a mask is a filter, too,” Dhanak says. The Centers for Disease Control and Prevention (CDC) advises mask wearing “in public settings and when around people who don’t live in your household, especially when other social distancing measures are difficult to maintain.” But experts says people should wear masks even when they are social distancing because of these far-spreading aerosols. “It’s important to keep in mind that this virus is incredibly contagious,” says Sharon Stoll, DO, an immunologist and neurologist at Yale Medicine in New Haven, Connecticut. Even if you’re further than six feet away from someone else, you should continue wearing your face mask to help mitigate the spread of the virus, especially indoors, she says. Don’t think that wearing a mask means you can linger in crowded indoor locations, especially bars and restaurants. “It’s all about the level of risk,” Dhanak says. “If you’re in a room with an asymptomatic person for three minutes versus three hours, it makes a big difference in how much you’ll be exposed.” RELATED: Do You Really Need to Wear a Mask This Summer?
