Restaurants are setting up tents and temporary structures to extend outdoor dining during the winter. But they come with their own hazards, and in some cases, could be riskier than eating indoors.

• Bars and restaurants have set up tents and other temporary structures to prolong outdoor dining as temperatures drop in many parts of the US.
• But Jaimie Meyer, an infectious disease physician at Yale Medicine and associate professor at Yale School of Medicine, told Business Insider that enclosed outdoor spaces could be risky for customers.
• "When you're making those outdoor spaces look a lot more like indoor spaces — so if they have, all of a sudden, three-and-a-half walls, or the air flow's not great, or there's lots of people still at a table, then you kind of get rid of all of the potential benefits of outside," Meyer said.
• Several cities and states have put rules in place for outdoor structures, mandating that 50% of the sides open and banning totally enclosed structures. In places like New York City, enclosed tents must be treated like indoor spaces and limited to 25% capacity.
• Totally enclosed tents and temporary buildings might even be riskier than dining inside a restaurant since they lack built-in ventilation systems to increase airflow, Meyer said.

As the temperature drops in many parts of the US, restaurants are coming up with creative solutions to allow for outdoor dining. But in some cases, these solutions may increase diners' coronavirus risk.

Since the onset of the pandemic, outdoor dining has allowed restaurants and bars to stay open while offering customers a way to continue eating, drinking, and socializing in a low-risk environment. Outdoor dining has become so popular and lucrative that it's becoming a more permanent fixture everywhere from Milwaukee to Boston.

But in the winter months, restaurants will be hard-pressed to convince diners to sit outdoors, exposed to chilly temperatures, wind, and possibly even snow.

Enter: tents, enclosed patios, and even curbside cabanas.

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City and state governments across the country seem somewhat split on what types of structures are safe. In Chicago, for example, the city mandates that temporary outdoor structures must have 50% of the sides open in order to ensure air flow. New York City has the same rule, but will allow fully enclosed structures - they'll just be regulated like indoor dining and capped at 25% capacity. Cities in Connecticut and Colorado have similar mandates.

State and local laws aside, however, infectious disease experts say this type of dining comes with clear risks that customers should take into account before dining in one of these structures.

Jaimie Meyer, an infectious disease physician at Yale Medicine and associate professor at Yale School of Medicine, told Business Insider last month that while she applauds businesses for thinking creatively about how to prolong outdoor dining, some are going too far and essentially creating an indoor space.

"When you're making those outdoor spaces look a lot more like indoor spaces - so if they have, all of a sudden, three-and-a-half walls, or the air flow's not great, or there's lots of people still at a table, then you kind of get rid of all of the potential benefits of outside," Meyer said.

Meyer said the two keys to safe outdoor dining are the ability to physically distance and airflow. But structures like four-sided tents lack air circulation that restaurants have - businesses aren't installing ventilation systems in a temporary curbside hut, meaning dining in an enclosed space like that could be even riskier than sitting inside at a restaurant, Meyer said.

"You don't want air to essentially be stagnant," Meyer said. "That's especially true in the winter because when there's less humidity in the air the droplets can actually disperse farther."

Meyer suggested bars and restaurants add a fan if they're going to have an enclosed outdoor space, or just lift a tent flap or leave a window open - anything to keep air circulating throughout the structure.

Beyond the inherent risks associated with little air flow and close proximity to other people, Meyer warned that outdoor dining structures may give people a false sense of security. Since they're not technically inside the restaurant, diners may relax social distancing measures, move around without their masks on, or otherwise treat it as an outdoor space, even if, for all intents and purposes, it's more like being indoors.

In many parts of the country, especially in places that experience wintry weather like New York or Chicago, restaurants have set up igloos and greenhouses that allow customers to dine, essentially, in a bubble. While those individual tents carry the same risks - namely, no ventilation - Meyer said they're a better solution as long as you only dine with people in your household.

"Some virus particles can be aerosolized and kind of hang in the air, and they like to stick to surfaces like tables and chairs and potentially the inside of this bubble," Meyer said. "There need to be precautions in place for a little bit of downtime between customers and good cleaning and disinfecting practices in between in order to make that safe."

The US faces a dire COVID situation nationwide

Regardless of the precautions restaurants are taking with tents, igloos, and huts, Meyer said it's possible dining could be shut down again soon anyway as cases continue to rise.

Robert Mujica, New York State Gov. Andrew Cuomo's budget director, said during a press conference on Wednesday that bars and restaurants are the fastest-growing source of COVID infections in the state now that it's getting colder. Indoor dining is prohibited in parts of the state that have been deemed COVID "clusters," and Cuomo has warned that indoor dining could be shut down in New York City by Monday.

Other parts of the country are placing limits on restaurants as well. Both California and Michigan have shut down indoor dining, and Baltimore has closed all types of dining at restaurants, including outdoor service.

Last week, the CDC warned against spending time in "nonessential indoor spaces and crowded outdoor settings," calling those spaces "a preventable risk to all participants."

These measures amid a devastating COVID situation across the country. The US reported over 220,000 new COVID cases on Tuesday, and more than 104,000 people are currently hospitalized as a result of complications from COVID-19. The US has now seen more than 288,000 deaths since of the onset of the pandemic. It's difficult to measure which part of the country is currently the hardest hit by the virus - as The New York Times notes, several parts of the country could be considered the biggest hot spot depending on how you measure it.