CU Boulder studying air purifier effectiveness in K-12 schools

Oct. 4—University of Colorado Boulder researchers are using a $2.2 million grant from the Centers for Disease Control to investigate if improved air quality in classrooms with portable air purifiers can reduce absenteeism in K-12 schools.

CU Boulder Engineering Professor Mark Hernandez is co-leading the project with researchers at the University of Colorado's Anschutz Medical Campus.

"We want the kids to be healthy in class," he said. "We don't want them to get sick at school. We want the learning environment to be the best it can be. That's the desired outcome."

Over the past few months, Hernandez and his team — including eight engineering students — helped install and test air quality monitors in 2,400 classrooms, according to a news release. The monitors provide real-time data on classroom temperature, humidity, CO2 and air pollutant levels.

The team also has helped install air purifiers with high-efficiency particulate air, or HEPA, filters in about 30,000 classrooms statewide through the Colorado Department of Public Health and Environment's $5.5 million Clean Air for Schools Program. The St. Vrain Valley School District is among 28 districts statewide that have installed air purifiers in schools as part of the program.

Prior to that grant program, the Boulder Valley School District installed air purifiers in every learning space in the district in December 2020 as part of its efforts to reopen schools during the pandemic, Assistant Superintendent of Operations Rob Price said. The cost was covered by a Safe School Reopening Grant through the Colorado Department of Education.

The air purifiers — which the researchers tested to find the purifier brand that was effective and offered "the most bang for the buck" — can effectively filter out air pollutants, including particulate matter from vehicle exhaust and wildfire smoke, that can trigger allergies and asthma, according to the CU news release. They also remove airborne viruses like the coronavirus.

Hernandez described them as "the seatbelt for lungs."

"It doesn't mean you aren't going to get sick, but it lowers the odds," he said. "It helps the existing ventilation system do its job."

With the air purifiers and sensors in place, the CU team plans to compare student absenteeism rates in classrooms with air purifiers to those without them.

"No one has linked this to academic outcomes," Hernandez said.

Chronic absenteeism rose during the pandemic, both in Colorado and nationally, with education leaders worried the continued large number of students missing more than 10% of school is hampering academic recovery.

An analysis released this week by the Colorado Department of Education found nearly 270,000 of the state's public school students, or 31%, missed more than 10% of school in the 2022-23 school year.

That was the second highest number of chronic absences recorded, topped only by the 2021-22 school year during the pandemic, when 36% of students missed 10% or more of school, according to a news release. The state has calculated chronic absenteeism since 2016-17, with rates ranging from 18% to 24% prior to the pandemic.

Hernandez estimates it would cost $65 per student, per classroom, per year, to effectively reduce airborne particles with air purifiers installed in classrooms.

"That's cheaper than a textbook," he said.

While Boulder Valley isn't part of the current study, the district previously worked with Hernandez and the University of Tulsa on a comprehensive review of the district's indoor air quality that included recommendations for alternative systems and improvements to existing systems.

The district used the $576.5 million capital construction bond issue approved by voters in 2014 bond to pay for the improvements, with data collected before and after the renovations. While the researchers also planned to look for associations between the improvements and the total absence rate, Price said, the pandemic disrupted the district's data collection efforts.

Along with the renovations, the school district used a grant from the Colorado Department of Education to install installed CO2 sensors in every school, Price said, allowing the district to identify areas of poor ventilation and make changes.