Area schools are taking extra measures this year to filter pathogens out of the air inside their buildings.

Legacy Christian Academy has taken some of the most drastic steps, installing new ionization methods into its HVAC systems and placing mobile units throughout the campus.

Head of School Jake Mulvihill said the goal was to have all the students back on campus for five days a week when the school year started back in August.

The school began looking into options and connected with Iso-Aire, an air filtration company that recently developed a system to filter air for isolation rooms.

Iso-Aire began working with health care providers to increase isolation rooms at the beginning of the pandemic. To help accomplish that, the company developed units that combine ionization and high efficiency particulate air (HEPA) filters.

“After we created it for that use, we realized COVID-19 is not going away,” Kevin Albers who runs sales and marketing for Iso-Aire said. “There’s actually a huge need and benefit to businesses to provide that clean air indoors.”

LCA installed 18 ozone-free ionization units it its HVAC system and added six mobile ionization and filtration units in key locations around its buildings.

“My understanding is we’re the only kindergarten through 12th-grade school in Minnesota that is fully ionized,” Mulvihill said.

Ions pull hydrogen from viruses, making the virus ineffective at infection, Albers said. That works by damaging the protein coat viruses use to enter into human cells, according to Albers.

Another benefit from ionization is the ions cling to particles, enlarging them and making it easier to catch the particles in filters, he said.

The mobile units also contain a HEPA filter, which is rated for catching almost all particles that are .3 microns or larger, Albers said.

“Your typical HVAC filters are kind of like soccer nets, they capture some of the big stuff but all of the really small things are not really being caught,” Albers said.

Adding a HEPA filter isn’t as easy as dropping it into existing HVAC systems. The density and size of the filter can be too much for some systems to push air through.

“Since it is so much more filter media — think of it like a tighter screen — it’s too hard,” Kevin said. “Current HVAC systems are not designed to be able to pull that much air through such a restrictive filter.”

The Spring Lake Park School District started off in a good position, because it had relatively new air handling systems. The oldest had been replaced in 2008, Director of Student Services Tony Mayer said. That allowed SLP to swap to denser filters with higher MERV ratings.

Minimum Efficiency Reporting Values, or MERV, is a standard for a filter’s ability to capture particles between .3 and 10 microns in size.

“The higher the MERV rate the more stuff it’s going to pull out of the air — the finer the particles are going to be caught,” Facilities Supervisor Doug Stahl said.

SLP also has adjusted the amount of outside air those handlers take in. To keep air cleaner the district adjusted the outside air intake on handlers from 20% to 50%, Mayer said.

The buildings typically had a MERV 8 rating, but were increased to a MERV 13, Mayer said.

MERV 8 filters are capable of removing dust, mites and mold out of the air. MERV 13 filters can take bacteria and virus carriers out of the air, Stahl said.

The Anoka-Hennepin School District has focused on improving air exchange, flow and filtration, Chief Operations Officer Greg Cole said. The district is maintaining a minimum of 20% outside air in their buildings.

Anoka-Hennepin is upgrading its filters wherever it is possible. Buildings that had MERV 8 filters are being upgraded to MERV 11, which is the densest possible for those system. MERV 13 filters are being upgrade to MERV 15, Cole said.

While the district has been working to upgrade all of its HVAC systems since well before the pandemic, the systems that have yet to be upgraded are limited to MERV 11 filters.

“The higher that rating is, the harder it is for air to pass through them,” Cole said.

Two hours prior to occupancy the district is purging the air by performing two full air exchanges before the day starts, according to Cole.

More information about Anoka-Hennepin’s efforts can be found at

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