Tens of thousands of Michigan students are learning in classrooms with decades-old heating and ventilation systems that do little to limit the spread of COVID-19.

Across the U.S., few schools have invested in systems capable of pumping optimal amounts of fresh air into classrooms. The same holds true in the 285 Michigan schools that submitted information to the state in recent months about their heating and ventilation systems.

Few of those schools have filters capable of removing viral particles from the air, a key, experts say, to fighting the virus indoors.

“I would say that it is right up there right behind face masks,” said Stuart Batterman, a professor of environmental health sciences at University of Michigan and an expert on indoor air quality

“You want to have decent filters. When you cannot open a window or be near an open window, having clean air coming to you through a filtered system is kind of like the equivalent,” he said.

The districts shared information about their HVAC systems as part of a state program that offers guidance on using heating systems in schools to fight COVID-19. They have combined enrollments of 145,000, or nearly 10% of students in the state, almost half of whom were learning in-person at the time of the survey. In more than a quarter of the schools, HVAC systems hadn’t been updated in 20 years or more.

Scroll down to see if your school district responded to the state’s HVAC survey.

The state doesn’t fund improvements to those systems, leaving districts to rely on tax revenue from local communities. Many districts haven’t been able to afford the HVAC upgrades that would have helped them reduce the spread of COVID-19 in classrooms, although some have begun to make improvements with federal aid funds.

More students and teachers will likely report to classrooms this month than at any other point in the pandemic. New, more contagious variants of COVID-19 are spreading, and there is widespread concern about the safety of in-person learning.

There’s a lot any school can do to prevent infections in classrooms, even with an outdated HVAC system. They can require mask-wearing, sanitize surfaces, open windows, and keep class sizes small enough that students and teachers can space out. The available research and data suggest that Michigan schools have largely used these safety measures to prevent the virus from running rampant in classrooms.

But the fact remains that Michigan hasn’t invested enough in its schools to give them a critical tool in fighting COVID-19: up-to-date HVAC systems.

Nearly every student is attending class in person at Reynolds Elementary, a 350-student school in a rural area along Michigan’s southern border.

To limit the spread of COVID-19, students and staff wear masks and do their best to maintain 6 feet of separation. But their HVAC system isn’t much help. The school was built in 1955. The HVAC system was last updated in 1993, and it doesn’t use modern air filters.

“It’s kind of low tech,” said Principal Dennis Irelan. “Some teachers have windows open, fans blowing toward outside. We had classes outside as much as we could.”

The school has seen upwards of a dozen COVID-19 cases among students and staff since the fall. No one has fallen seriously ill so far, Irelan said.

When the school receives its share of federal coronavirus aid, Irelan said part of it will go toward installing modern heating ducts with air filters in the school.

“It’s working,” he said of the school’s efforts against COVID-19. “But we need to be better. Everyone is doing the best they can with what they’ve got.”


One of the ways the coronavirus passes between people is through the air.

As an infected person breathes out in an indoor space, more virus particles float in the air. As more particles accumulate, other people are more likely to inhale them and become infected.

Some solutions to this problem are cheap and readily accessible to schools. Masks work. So does opening windows or increasing air circulation to bring more virus-free air into the building.

Another effective, if more expensive option is removing viral particles that are already floating in the air.

This is where air filters — and MERV — come in. MERV stands for minimum efficiency reporting value. It indicates how efficiently a filter removes particles from the air.

Most MERV-rated filters improve the air quality in a school, but only filters rated 13 or higher reliably catch the virus, Batterman said.

A MERV rating of eight was the most common among survey respondents, with 154 districts saying they use filters rated 10 or less.

Out of 286 schools that responded to the survey, 46 said they had filters rated 13 or higher. Another 86 didn’t share a filter rating, said they didn’t know what their filters were rated, or, in the case of one district, simply wrote “no idea.”

Improving air filtration in schools won’t be easy.

For starters, any school HVAC system may need dozens of filters, which need to be replaced as often as monthly. A single, standard MERV 13 filter of the type used in schools costs $20 online. The costs add up.

Even if districts could pay for filters, many don’t have systems capable of accommodating a MERV 13. Strong fans are required to push air through a MERV 13 filter.

“The higher the [MERV rating] the more it filters, but then the more resistance it has,” said Tom Kasefang, director of maintenance for the Lenawee Intermediate School District in Michigan’s Upper Peninsula.

The district’s seven buildings were mostly built in the 1960s and ‘70s, and “some of the older systems aren’t capable of pushing the air through,” he said.

The district largely uses MERV 8 filters.

Kasefang knows that those filters won’t remove coronavirus particles from the air. He has compensated by increasing the amount of fresh air pulled in by the HVAC systems.

So far, the district has reported 82 COVID-19 cases among more than 1,400 students and staff, including more than five cases this week that shut down several district buildings

Why don’t Michigan schools have up-to-date HVAC systems?

The answer comes down to funding.

Many schools haven’t invested in classroom air quality for decades due to a lack of funding and a lack of knowledge about the benefits of the invisible improvements, experts say.

“They just don’t have the money to do a lot of” air filtration and air circulation, said Jim Newman, a fellow at the Engineering Society of Detroit and an expert on indoor air quality. “That’s been the real problem.”

Funding for facilities improvements such as air circulation generally comes from a school’s local community, not the state.

Local school boards must ask residents to pay more in taxes to make major improvements. That’s much easier to do in wealthy areas, where high property values mean even a small tax increase can bring in enough money to make major repairs.

And it’s why school districts in low-income areas are least likely to have up-to-date HVAC systems now.

“The way that we fund capital improvements in the state is very disparate,” said Peter Spadafore, communications director for the Michigan Association of Superintendents and Administrators.

Some schools are using federal COVID-19 relief funds, Spadafore said. Brandon School District in southeast Michigan upgraded all of its air filters and put additional, portable air purifiers in classrooms.

“For in-person learning, MERV 13 filters and air purifiers rank at the top along with social distancing and mask-wearing,” said Karl Heidrich, interim superintendent of the Brandon district.

Download the complete Michigan K12 HVAC Survey Results as of (as of Jan 20, 2021)