Air quality experts agree, that weather permitting, maximizing access to fresh air is one of the best options for businesses trying to prevent airborne transmission of COVID-19 in their establishments. 
The simplest way of doing this is either opening more windows or conducting business outside, which is how many restaurants and even retailers have stayed afloat over the warm summer months. 
In sunny, temperate San Francisco, these options were even more feasible — that is until a series of devastating wildfires swept across the West Coast and caused outdoor air quality to plummet. 
The situation has turned conventional wisdom surrounding indoor air quality and coronavirus on its head. 
"If you're sucking air from outdoors to indoors, which is what they're recommending you do to decrease COVID, you're sucking in really poor quality air to start with," said Dave Karraker, co-owner of MX3 Fitness, which has two gym locations in San Francisco.  
Prior to the fires, the independent gym had set up an outdoor workout area on the sidewalk and in parking spaces in front of its one reopened location. But after several days of poor air quality, the city, on Friday, September 11, gave gyms the go-ahead to open indoors. 
"We didn't get the actual guidelines for that until 6 a.m. Monday morning, the day we were supposed to reopen," Karraker said. 
Luckily, he explained, the gym had taken steps to prepare, including replacing filters and setting up air purifiers throughout the 1,800-square-foot gym. It's also using fans to blow stale air out of the building through the front door — assuming air quality is safe enough to keep it open. 
Making these investments has meant spending thousands of dollars on upgrades after months of pulling in no revenue during the shutdown. 
"These are all small businesses that have not gotten any meaningful revenue since March," said Karraker, who also heads a coalition of independently owned gyms in the city. "The idea that somebody might be able to buy a brand new HVAC system would be a major stretch."
In the Bay Area, however, air conditioning and heating is a rarity. So once the wildfires die down, businesses will have the option of further opening up their buildings to fresh air. 
In more seasonal climates, the coming winter will present a challenge to businesses looking to bring people inside. 
Film Forum, a nonprofit movie theater in New York City, has already started investing in air quality upgrades, as it joins other independent theaters pushing Gov. Andrew Cuomo to allow them to reopen. 
Without the option of throwing open more windows or moving their screenings outside — an impossibility in downtown Manhattan — social distancing, plastic barriers, and filters have become the go-to fixes. 
So far, Film Forum has installed MERV 13 filters in the lobby and theaters. These high-grade filters catch airborne particles carrying the virus and are usually used in hospital settings, but have become widely adopted during the pandemic. New York has already required them for gyms, which were allowed to open earlier this month at 33 percent capacity. 
The filters were costly, said general manager Chad Bolton, but worth it to "show the governor and elected officials that we were serious about creating a safe space."
"Given the fact that we've been closed since March 15 and have not sold one ticket in six months, any expense is really felt at this point," he said.
The state has not specified yet what will be required of movie theaters in order to reopen, leaving them to look around at other states and industries for clues. 
"We're taking a best guess as to what will be expected of theaters, but we don't know," said Bolton.
For now, that means air filters and social distancing practices, as opposed to a full overhaul of their HVAC system. "So many of us are constrained by the systems we have in place," he said.