Putting ‘Emerging Technology’ Air Purification Devices to the Test

A news article published by CNN health on May 3, 2021 has nailed it when it comes to the types of questions that need to be asked about the efficacy of “emerging technologies” for the fight against COVID-19 and safe indoor air. As the pandemic progressed, an increasing recognition evolved about the role of aerosol transmission and technologies to improve indoor air quality through building ventilation. There are many ways to improve indoor air quality using existing and proven technologies like air filtration (upgrade air filters) and bringing in more outside air (open windows, doors, and outside-air dampers on air handlers). The problem is that these approaches have an energy penalty and cost building operators more money. Thus the attraction of many new-to-market air purifier devices, or as the CDC calls them “emerging technologies”. Emerging technologies include air “purification” devices that generate ions, emit UV light, or employ biocidal catalytic filter media. Many of these technologies are proven in principle to work under controlled laboratory conditions, but how those lab results translate to efficacy in real-world as-installed environments in occupied buildings is a totally different question.

Recently a peer reviewed manuscript was released in the journal Building and Environment (Zeng, et al 2021) that evaluated one of the more popular emerging technology devices on the market, a device manufactured by Global Plasma Solutions (GPS) that uses needlepoint bi-polar ionization (NPBI) technology. This is the same device manufacturer referenced in the critical review article by CNN health. In the Zeng manuscript, researchers from the Illinois Institute of Technology (IIT) evaluated the performance of a GPS bi-polar ionizer in a realistic sized room (not a “shoebox” sized benchtop enclosure like the GPS manufacturer study conducted as a basis for marketing claims). The IIT research presents concerning findings about unintended consequences of operating the GPS devices, such as increases of undesirable indoor air pollutants like VOCs (acetone, ethanol, toluene), and only marginal improvement to parameters like ultrafine particles for which GPS makes its strongest marketing claims.

RHP conducted our own in-house critical review of the manufacturer research studies posted on the GPS website that raised many questions. Some of the device performance statements appear unsubstantiated by the underlying science in that the test conditions under which the data was generated does not translate to real-world conditions in occupied buildings. Taking one small 2” piece of leather that has been sprayed with SARS-CoV-2 and blasting it with 27,000 ions/cc to show a 99.99% “overall average decrease in active virus after 30 minutes” does not translate into these devices being meaningfully effective at reducing the risk of airborne virus transmission in a real-world building setting. I have yet to review a convincing well designed study that would substantiate such a claim for needle-point bipolar ionization devices.

Test classroom at RHP’s Exposure Sciences Laboratory where the performance of two needlepoint bi-polar ionization devices were tested against various ventilation conditions and aerosol challenge agents.

RHP also conducted our own experimentation with two GPS needle-point bipolar ionization devices in our Exposure Sciences Laboratory to investigate what it would take to generate 27,000 ions/cc in a room that was realistically sized like a classroom. We constructed a 20 ft x 40 ft room with lay-in ceiling and plumbed it with a ventilation system. We installed two GPS-FC48-AC ionizers into the ventilation system. Each unit is rated by the manufacturer to “handle up to 4,800 CFM” of airflow, and therefore two of these devices should more than suffice for a room the size of our test chamber. When we turned on the units and provided “typical” airflow to the room as one would expect for a classroom setting with a reasonable occupant density, the concentration of ions in the room was about 1,000 to 2,000 ions/cc which is much lower than the 27,000 ions/cc that GPS reported in its testing that underpins the basis of the COVID-killing efficacy claims. Next, we dialed up the airflow. To generate and maintain more than 20,000 ions/cc in the air within our test classroom required over 2,200 CFM of airflow (about double what one would expect for a room this size), and more importantly it required conditions like a wind tunnel just like the wind speed in the Innovative Bioanalysis study conducted on GPS units that reported test conditions had average airflow speeds of 2,133 ft/minute (24 mph). I’ve never been in a classroom with 24 mph winds; that’s not a realistic test condition. This is a great example of a point that the EPA makes on its webpage titled “Can air cleaning devices that use bipolar ionization, including portable air cleaners and in-duct air cleaners used in HVAC systems, protect me from COVID-19?” when it states, “This is an emerging technology, and little research is available that evaluates it outside of lab conditions.”

I’m a believer in technology and would really be thrilled to see an emerging ventilation technology proven effective for COVID-19 risk reduction while reducing the energy penalty that tried-and-true approaches like filtration and dilution ventilation provide. I just haven’t yet seen a well-designed study showing how needle-point bipolar ionization accomplishes this in a real-world setting. Hopefully it’s forthcoming and if I were a building owner that spent tens of thousands of dollars on these devices based upon device manufacturer performance claims, I would demand to see the evidence. Questions need to be asked that appropriately challenge manufacturer claims and seek to understand how those performance claims relate back to the real-world conditions under which the devices are being installed.

Jacob Persky, MPH, CIH