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Outdoor diners who want to reduce their infection risk belong in the hot seat. Here's why.

Electric fan at Lewis BBQ

Electric fan at Lewis BBQ. Hanna Raskin/Staff

Epidemiologists agree that if you must eat at a restaurant, there’s less risk associated with dining outside. But not every patio seat is equally safe.

With temperatures rising across the Lowcountry, restaurant owners are outfitting their decks and commandeered parking lots with devices to keep customers cool. Yet the same familiar fan that promotes sweat evaporation, which is the mechanism for refreshing those in its wake, is also a champ at delivering dangerous droplets.

According to Edward Nardell, professor of environmental health, immunology and infectious diseases at the Harvard T.H. Chan School of Public Health, people who want to avoid contracting the coronavirus should not sit in the direct path of an electric fan, especially if there’s an occupied table between the fan and the table they’re considering.

“Air movement is a double-edged sword,” Nardell says. “It can help carry away infectious droplets and infectious airborne particles, but it can also carry larger droplets from one table to another.”

For that reason, he advises restaurant owners to think carefully about their fan setup.

“The placement deserves serious engineering to be sure people are not sitting downwind,” he says.

Still, he emphasizes that eating outdoors is a better strategy than finding a seat within an air-conditioned dining room. In a recent talk sponsored by the Massachusetts Consortium on Pathogen Readiness, Nardell suggested that the South’s reliance on air conditioning could help explain why its number of COVID-19 cases is currently surging.

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“As people go indoors in hot weather and the rebreathed air fraction goes up, the risk of infection is quite dramatic,” he said of the threat posed by airborne transmission, comparing the burrowing behavior of Southerners in the summer to how Northerners nest in the winter.

The Centers for Disease Control and Prevention late last month revised its publication on restaurants and bars, rating “On-site dining with both indoor and outdoor seating. Seating capacity not reduced and tables not spaced at least 6 feet apart,” as the highest risk operation in terms of potential COVID-19 spread, with “Food service limited to drive-through, delivery, take-out, and curb-side pickup” at the other end of the spectrum.

Outdoor seating with spaced-out tables is classified as “More Risk.”

Scientists don’t yet know if that risk rises or falls in the vicinity of a misting pump or fogging system.

“Misters are an unknown,” Nardell says. They “potentially increase humidity and reduce evaporation of infectious droplets, encouraging them to settle, but not if there is a fan or breeze.”

Diners may just have to sweat it out.

Reach Hanna Raskin at 843-937-5560 and follow her on Twitter @hannaraskin.

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