The Centers for Disease Control updated their “Ventilation in Buildings” guidelines to five air changes per hour in May to help prevent airborne disease transmission. Fresh, filtered and recirculated air proved to be effective tools in the fight against COVID-19.

During the Canadian wildfires however, fresh air became more of a liability at certain times of day. Many offices in the U.S. ended up having better air quality than homes in the same areas, owing to a better building envelope and air exchange rates that kept indoor air circulating, selectively drawing in outside air when air quality was better.

The variability in indoor air quality problems and strategies makes adopting air sensing technology across public spaces a “no brainer,” said Mark Hernandez, a Professor of Civil and Environmental Engineering at the University of Colorado Boulder. That’s why he’s pushing schools in his state and across the country to adopt air sensing technology that many LEED and Fitwel certified commercial and institutional buildings already deploy.

“We should have been doing this all along. It's affordable. It’s 0.001% of building operating budget. Would you drive your car without knowing the performance of it?” Hernandez asked. “There’s no excuse not to have this. Especially with kids, they have no choice but to go to school.”

Air quality monitoring company Attune is now in thousands of classrooms across the country, said Serene Almomen, CEO. With her company’s flagship air sensor package, most schools just opt for temperature, humidity, particulate matter, volatile organic carbon, CO2: from these parameters building managers can affordably and accurately estimate a rooms’ fresh air exchange rate.

Assuming the room air is well-mixed, knowing the removal rates is a strong proxy for lowering respiratory exposures to potential pathogens suspended in indoor air. Expensive biosensors are usually reserved for detection in special environments (i.e. military application, pharmaceutical preparations etc.). Attune likewise does not include specialized fluorescent mold detection, but sustained high levels of humidity provide a proxy there as well.

Across the schools that have adopted Attune, Hernandez says there’s a common trend that’s emerged every time they turn on their ventilation systems in the morning after turning them off overnight to save energy. Data shows that this energy saving tactic can come with the tradeoff of disturbing settled dust in ducts.

“When the ventilation system kicks on, there's a big pressure spike and that lifts a bunch of stuff. But we see it both with fine and coarse particulate matter, which suggests probably the ducts need to be cleaned. Or the filters are being overwhelmed, or they're not installed properly,” Hernandez said, adding that while VOCs build up overnight without ventilation, sensors can be used to confirm they’re cleaned out by the time classes start.

The Leadership in Energy and Environmental Design (LEED) and Fitwel programs award points to facilities that do spot checks on indoor air quality with handheld devices, and offer even more points for using real time monitors that don’t require going out into the field and taking measurements manually. Hernandez said that like smoke detectors, they’re best positioned near the return air collection points (often on the ceiling); this positioning offers the best composite data for exposure analyses and ventilation performance.

Almomen said that Clark County Public School district recently installed Attune, operating on the suspicion that CO₂ levels were too high in the facilities, causing the conditioned spaces to feel “stuffy.” They thought they needed to start bringing more fresh air than their system is currently designed for.

“They found their CO₂ levels were in line with expectations, but that temperature and humidity were out of whack,” Almomen concluded. “That helped inform them on how to fix the underlying problem. And that’s really where this sensing technology comes into play. It’s a reliable diagnostic tool for keying in optimal settings.”