The pandemic is one problem for air quality in the classroom. Wildfire smoke is another.
On a late September day in northeast Wyoming, the air was crisp and cool, and the afternoon sun sat low in the sky. The conditions were just right for the Tongue River High School cross country team.
"This is like my kind of weather," said Marajah Pease, a junior on the team. But earlier in the season, the team was dealt several days where the weather wasn't so ideal.
"When it's smoky, it just, like, dries your throat, and it's kind of hard to breathe and try to motivate yourself to keep going, especially during an actual race," Pease said.
In past years, Coach Laine Parrish mostly looked at the weather forecast for temperatures, and rain or snow, to see if it would be a good day for practice. Now, he has other concerns.
"This year, we've had to look at Air Quality Index, and especially in the first week, it was bad," he said.
The AQI rose above 100 earlier in the season, which is considered unhealthy for children. Parish said when it was that bad, the team took a bus up Black Mountain where conditions tended to be better.
Researchers say wildfire smoke is an increasing threat to children. And the problem isn't just outside. When smoke's around for a long time, contaminated air ends up indoors, like in classrooms and school gyms.
Roy Anderson is the emergency manager for the Washoe County School District in Nevada, which includes Reno.
"We really had some poor - really poor - air quality days, where we actually did have to close school," he said.
Last year, the district moved classes online ten separate days because of wildfire smoke. That's also happened several times this fall.
Anderson said there's not an exact AQI that will cause the district to cancel school. Instead, they consider a number of things, such as weather patterns and how long kids waiting for the bus might be exposed to hazardous air. But coming up with a policy was a challenge.
"When we were doing our research looking at what other districts do, there really wasn't a lot of guidance out there," he said.
Since then, the federal government has provided some help. In June, the Environmental Protection Agency, along with the National Institute of Standards and Technology and an association of HVAC engineers, released interim guidelines for schools, as well as commercial and public buildings.
The guidelines describe how schools can reduce exposure to the fine particulate matter - known as PM2.5 - in wildfire smoke. These particulates are so small they can travel deep into the lungs, and even enter the bloodstream.
Sarah Coefield, an air quality specialist with the Missoula City-County Health Department in Montana, said the guidelines are a critical step in establishing PM2.5 standards for indoor air quality.
"There is no requirement that your indoor air have a reduced particulate concentration, and so it is a bit of a free for all right now," she said.
In other words, schools aren't required to test or clean air that is contaminated by wildfire smoke. And new research suggests that indoor air isn't necessarily cleaner. So while the new guidelines don't set enforceable standards, Coefield said building managers have a good place to begin.
"There's more to it than just even replacing the filter with a better filter," she said.
For example, building managers need to see if their HVAC system can handle a higher efficiency filter before adding it. The guidelines suggest conducting a full maintenance check on the HVAC system, and to make repairs if needed.
During one indoor air quality study for commercial and public buildings in Missoula that Coefield was involved with, researchers encountered a lot of deferred maintenance on HVAC systems in commercial buildings.
"That really impacted the indoor air quality. It wouldn't even really matter what kind of filter you had in the system because your HVAC was broken," she said.
The guidelines also suggest purchasing air sensors as a way of telling how bad the problem is to begin with.
Colleen Reid is a geography professor at University of Colorado Boulder who researches environmental impacts on health. She said Denver schools stay open if officials approximate that air quality is better there than at children's homes. But there's at least one problem with that.
"No one has that data," she said.
But Reid just received an EPA grant to get the data. She and a group of researchers will place air sensors in Denver-area schools and homes to help determine whether it's safer for kids to stay home or go to school.
Meanwhile, the EPA is working with industry to come up with final guidelines on keeping indoor air safe. Those are expected in 2022.
This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNR in Nevada, the O'Connor Center for the Rocky Mountain West in Montana, KUNC in Colorado, KUNM in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.