News and Notes

APS’ Ionizers Got Lab Tested: The Results Weren’t Great

by | Aug 24, 2021 | News & Press Releases, Ventilation

We have received the results from the Illinois Institute of Technology lab that is evaluating the efficacy of electronic air cleaners.

They tested the Blueair 211 units (which APS bought). Results are disappointing to us.

๐Ÿ“Œ Project:

๐Ÿ“Œ Report:

Ionizer Inside

There was some inaccurate information being put forth that these machines were not ionizers, because they were not listed by the California @AirResources Board as ionization devices.

But these machines do indeed have an ionizer. ๐Ÿ‘‡


The use of additive and electronic air cleaning devices, often marketed with HEPA in the name although they ARE NOT HEPA cleaners, has come under scrutiny this year. This is a good article:

Scientists have raised concerns about some kinds of air cleaners because they may emit a lot of ozone.

California @AirResources Board checks this out, and we FOIA’d documents. The Blueair filters that APS got do not create ozone, according to public records provided by CARB.

Ozone is not the problem with these particular machines, although it is a factor for other brands.

Ozone Documents

Scientists have also raised concerns about how shooting ions into the air can create chemical reactions with what’s in the room โ€” that result in “gas-phase organic compounds (VOCs, aldehydes).” This is why we’re concerned about the use of this technology, which is specifically NOT recommended by health and air quality experts.

Here’s a list of byproducts that scientists have looked for when ionizers are in use, that are possible:

Possible Byproducts of Ionization


Performance Results

This new testing showed that ionization is critical to Blueair’s Clean Air Delivery Rate, because it causes things to stick to the filter. The filter didn’t perform so well without the marketed “electrostatic” energy making particles more clingy. (Shown in charts.)


Testing Results 1

Specifically, when the ionization component was disconnected inside units, these electronic air cleaners performed 44% worse for the very smallest particles. Univ. of Florida scientists found the smallest particles contain infectious virus, so these machines may need ionization turned on to catch SARS-CoV-2 virus particles as advertised.

It would have been more cost effective just to DIY this effort, it turns out, than to purchase the units that APS bought.


The recent testing presented an independent review of the certified CADR (Clean Air Delivery Rate), a measure of how fast and well they filter. CADR for smoke, dust, and pollen particles during normal operation (with ionizer enabled) were estimated to be 285, 309, and 389 CFM.

In the independent university test, these portable filters that APS got performed about 19% worse than we had expected, compared with their AHAM certification from the air cleaner industry group. Illinois Tech engineers tested three different Blueair units rigorously, and are continuing their work to provide totally independent analysis of such units for consumers and groups like schools.

As a result, all of APS’ ventilation calculations are likely incorrect, and they may have UNDERESTIMATED the amount of clean air our kids will have in many classrooms, since the ionizers they placed in rooms produce 19% less clean air.

Can APS disable the ionizers and just use the filters in these machines?

During the worst part of the pandemic, most of our members feel like disabling the ionizers would NOT be a good idea if they’re all we’ve got in classrooms. Because the machines perform even worse without the ionization.

Another sad thing is that APS has signed up to buy expensive replacement filters for these machines, filters which will likely cost APS as much as real HEPA filters would have cost.

But “True HEPA” filters would have removed 99.97% of dust, bacteria and particles <0.3 ยตm, w/o any ionization needed. Top experts like @CorsIAQ strongly recommended buy only True HEPA, because these machines don’t add anything to the air in a room and don’t cause unpredictable chemical reactions.

Parents and teachers asked APS NOT to purchase any air cleaner with ionization last fall, and made it very clear they were concerned about possible chemical byproducts of this technology. We certainly understood that APS had agreed to stay away from ionization technology, and it’s unfortunate that it is so hard for schools to get all the information they need to make the best buying choices.

Blueair’s marketing material says it uses “electrostatic filtration” and distances itself from “air cleaning techniques based only on ionization.” That’s the only time ionization is mentioned.

They call themselves HEPASilent, but the filter media is NOT actually a True HEPA filter, capable of achieving the highest level of filtration for small particles. ย  A few more tweets we posted with resources for further research on the impacts of ionization and these issues, which many school districts across the USA are struggling with:

Earlier this year, we tried to convince our VA senators @MarkWarner and @timkaine to please write STRONG guidelines so schools would spend $$ on products that are proven, like True HEPA air cleaners. It didn’t happen.

It’s ironic we were watching out for this stuff, but now we have 2,000+ air cleaners, shooting a very high amount of negative ions into our classroom air. They will remove virus in the air, or cause the viral particles to come out of the air and stick to something in the classroom. But they may hurt IAQ in other ways.

APS should not buy any more of these ionization units and should switch to a different model of True HEPA cleaner, and add True HEPAs to our classrooms. This would achieve a higher number of air changes, we hope.

When our community’s level of COVID-19 is reduced back to low or medium transmission, APS could then perhaps turn off the ionizers, and even take the time to disable the ionization device in each machine. Without ionization, these machines could be used as a basic filter that provides maybe 1 or 2 extra air changes, and modestly boosts a room’s clean air, in addition to a better True HEPA filter in the classrooms.

Every bit of clean air counts this year, and it would be better to set the goal as high as possible, given the current state of the pandemic. Perhaps APS can even become a leader in sticking up for schools all across the USA who made such purchases, too. There are so many.