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Bipolar Ionization – What is It & How Does It Work?

The COVID-19 pandemic had a direct impact on people’s perception and understanding of indoor air quality (IAQ) and has helped to point out the health benefits of improving IAQ within high-occupancy buildings. Among many new filtration and air cleaning technologies that have been explored through the years to improve IAQ, bipolar ionization (also known as needlepoint bipolar ionization) has surfaced in recent years as a potentially effective way to clean air and reduce viral transmissions within buildings. As a newer technology, it has also gone through rigorous scrutiny from the scientific community, all while further testing is being conducted to prove its efficacy in airborne contaminant transmission prevention. But what exactly is bipolar ionization and how does it work?


What is Bipolar ionization?

Bipolar ionization in basic terms splits air molecules in the air stream by passing the air through a plasma field, generating positively and negatively charged ions (hydrogen and oxygen), which can then attract and join with airborne contaminants or

particles. Once the particle joins with an ion, it becomes heavier and larger than the surrounding air, increasing the chance of the particle to be trapped in a filter. This sort of technology can also be used in smaller applications within a room, where the heavier charged pathogens sink to the bottom of the air purifier, reducing the chance of the pathogen re-circulating into the room breathing zone.


Figure 1: The diagram above illustrates increased filtration effectiveness after the charged and enlarged airborne particles encounter a filter. https://www.ashrae.org/technical-resources/filtration-disinfection


How does this technology compare to previously existing air purification alternatives?

Ultraviolet energy (UV-C) has been used as a proven method to stop the spread of viral, bacterial, and fungal organisms within the air by killing and inactivating the airborne organisms so they are unable to replicate and spread. This method of air decontamination has been used inside air handling units, within the ductwork, or in portable room decontamination units (to be activated when the room is unoccupied). The UV-C wavelength provides the greatest germicidal effect by damaging cell DNA and RNA, but as a result, also requires special protective equipment to prevent damage to eyes and/or skin from UV-C overexposure. To prevent overexposure during system maintenance, UV systems should be turned off and maintenance workers should receive special training prior to working on UV-C systems. Similar to UV-C, some bipolar ionization products have been known to generate ozone and have been identified as harmful with prolonged exposure, so safety precautions need to also be taken when maintaining bipolar ionization equipment.


Ionization air cleaners have become prevalent during the COVID-19 pandemic, where many manufacturers have developed ways of generating reactive ions from air passing through high-voltage electrodes. As far as air cleaning technologies go, bipolar ionization is still very new, so widespread adoption of this technology can be difficult to achieve. Provided bipolar ionization device manufacturers can prove efficacy in their equipment, the equipment can be advertised as being a leading piece of technology to help remove viruses (like COVID-19) or to disinfect surfaces. The evidence proving the efficacy and safety of bipolar ionization is still being established and will probably take some time for the scientific community to fully adopt. Peer-reviewed studies do not currently exist on bipolar ionization, and as a result manufacturer data should be carefully considered when deciding whether to include bipolar ionization in a design.



Written by:

Kevin Barrow

Mechanical Design Engineer

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Sources:
  1. “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?” EPA, Environmental Protection Agency, 26 Apr. 2022, https://www.epa.gov/coronavirus/can-air-cleaning-devices-use-bipolar-ionization-including-portable-air-cleaners-and

  2. Filtration / Disinfection, 7 May 2021, https://www.ashrae.org/technical-resources/filtration-disinfection

  3. “What Is Bipolar Ionization?” Sanalife, Sanalife, 10 Aug. 2021, https://www.sanalifewellness.com/blog/what-is-bipolar-ionization