With more cold weather approaching, local restaurants are installing enclosed tents outside. Back in 2013, the City had battled restaurants over using tents in an effort to protect "the historic character" of downtown and west main, but now, according to Assistant Zoning Administrator Craig Fabio, the City has provided temporary allowances for tenting of outdoor café spaces.

"The permit requirements address fire safety," says Fabio. "Additionally, each establishment must remain in compliance with the temporary restrictions put in place by the Governor’s office and the Health Department regarding occupancy, enclosed spaces and social distancing."

However, the recent guidelines from the Governor, as well as the City's regulations, don't specifically address the main concern that many expert have about outside tents and structures -- the need for proper air circulation.

"It has to do with ventilation," said Anne Rimoin, Professor of Epidemiology at UCLA, on ABC’s Good Morning America earlier this month. "The ability of this virus to be able to dissipate in the air. Tents don't have ventilation the way an indoor restaurant would. So these outdoor settings are not actually outdoors."

GMA also spoke to Virginia Tech engineering professor Linsey Marr, an expert in the airborne transmission of viruses, profiled here in the New York Times in July.

"If someone is infected and they're sitting outdoors in one of these tents, when they're breathing and talking, they release viruses into the air and just like cigarette smoke, the air can easily flow in any direction because there are no walls," Marr said. "And once you start adding walls, you potentially block that wind. Once you add four walls, you kind of lose that benefit of being outdoors."

Shaun Thomas, an environmental health technical specialist with the Thomas Jefferson Health District, says an outdoor tent with four walls is considered the same as indoor seating and must meet the mandate requirements for indoor seating, which includes a masks requirement when customers are not eating or drinking, required social distancing of patrons (more than 6 feet of spacing from other parties) and reduced occupancy.

Given that many outdoor tents will not have an HVAC system, air exchange and air flow rates may or may not equal those of the fixed facility, says Thomas, recommending that food-service operators employ the services of a licensed HVAC contractor to design an air handling plan that would meet or exceed that of the fixed facility. Conductive heaters are recommended (over blowers) for use in heating an enclosed outdoor space, she says.

"Customers should be aware that tents with poor air exchange/air flow may allow for the airborne COVID-19 load to be potentially higher," says Thomas.

Thomas recommends that restaurants consult this temporary outdoor seating guidance published by the International Code Council (ICC).

Due to the volume of emails she receives, Marr said she couldn't immediately respond to further questions from The DTM, but she recommended consulting this FAQ her team created about protecting yourself from COVID-19 aerosol transmission.