August 10, 2021
Last Updated On:
March 6, 2023

What Is Bipolar Ionization?

Understanding Bipolar Ionization (NBPI) safety considerations, how it works, and how it reduces airborne pathogens.

Last Updated On:
March 6, 2023

Portable and HVAC Induct air purifiers are convenient devices that instantly amplify the air cleaning in a given space. Considering the impact the COVID-19 pandemic has had on indoor air quality (IAQ), it's no surprise that many of us are trying to become subject matter experts on traditional and electronic air purifier technologies.

With offices, schools, and universities installing multiple forms of traditional and electronic air cleaning technologies in their facilities, it is essential to understand their impact on occupied indoor environments. Amongst all these air purifier technologies, Bipolar Ionization has become the focus of numerous facilities in both public and private sectors nationwide.

In this article, the technology subject matter experts at Sanalife have entirely broken down Bipolar Ionization technology from function to benefits and safety considerations.

Ionizer Air Ions Generators

What Is Bipolar Ionization Technology?

Bipolar Ionization technology, also known as Needle-Point Bipolar Ionization (NPBI), is a method of air purification that generates positively and negatively charged particles into an environment to clean the air. Bipolar Ionization is often installed directly into existing HVAC systems and ductwork within commercial or education facilities. Induct Bipolar Ionization systems are compact, high-voltage devices that require "downstream" airflow to distribute ions into an indoor environment. Portable air purifiers that feature "ionization technology" typically use a lower-voltage variation of Bipolar Ionization, commonly called "Negative Ionization" or "Plasma Ion Generation."

How Bi-Polar Ionization Works Diagram
How Bi-Polar Ionization Works Diagram (Source: Modern Castle)

How Does Bipolar Ionization Technology or NPBI Devices Work?

Bipolar Ionization works to "purify" indoor air by injecting ions into the air to attract and charge airborne particulate. The "Bipolar" in this form of air purification comes from the technology's ability to add or subtract electrons from air molecules producing a positive and negative charge. Air purification systems that use Bipolar Ionization generate ions through two primary methods; Corona Discharge and Brush-Type Discharge.

Bipolar Ionization Air Ion Formation Diagram

Corona Discharge Method - Bipolar Ionization:

HVAC Bipolar Ionization systems typically use the Corona Discharge method to create a strong ionization field to distribute ions within high-density commercial environments. The Corona Discharge method uses a conductive needle or two conductive metal plates and high-voltage electricity to create an electrical field to ionize the surrounding air.

Brush-Type Discharge Method - Bipolar Ionization:

HVAC ionization systems covering less-dense indoor environments typically use the Brush-Type Discharge or "Brush Discharge" method. The Brush Discharge method works by emitting low-voltage electricity through fiber brushes to produce an electrical charge ionizing the surrounding air.

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How Does Bipolar Ionization Reduce Airborne Contaminants?

When deployed in indoor environments, the ions and energy field produced by Bipolar Ionization can reduce airborne contaminants and pathogens in two different ways. The primary function of the ions produced by Bipolar Ionization is to add mass to airborne particles. 

The increased particulate mass in ideal scenarios helps air filtration systems such as HVAC systems with MERV 13 filters or portable HEPA air purifiers increase efficiency in capturing the airborne particulate. However, these ionized airborne particles often fall out of the air onto surfaces, making them susceptible to reanimation by movement within the space.

The secondary function of Bipolar Ionization is the creation of Hydroxyl Radicals (OH). In the Corona and Brush-Type Discharge methods of BiPolar Ionization, the energy field can split water vapor molecules in the air, producing Oxygen Oxides (O2-) and Hydrogen Ions (H+). These molecules sometimes rejoin, creating clusters of Hydroxyl Radicals (OH), which can target the hydrogen within airborne pathogens and microorganisms.

HVAC Induct Bipolar Ionization In An Office Environment

Does Bipolar Ionization Reduce CO2 Levels? 

While Bipolar Ionization can improve indoor air quality by reducing airborne contaminants, it does not directly address the presence of CO2 in the air. To effectively reduce CO2 levels in indoor spaces, it is necessary to increase ventilation or introduce air quality systems specifically designed to scrub carbon dioxide from the air. Employing Bipolar Ionization may not improve indoor CO2 levels as opposed to recommended air quality improvements discussed in the ASHRAE 62.1 Ventilation Rate Procedure.

Can Bipolar Ionization Reduce Airborne Viruses, Including COVID-19?

Studies have demonstrated Bipolar Ionization to effectively remove particulate matter from the air and reduce airborne viruses and bacteria. However, similar to many ion-emitting air purification technologies, Bipolar Ionization is still subject to further research and evaluation to determine efficacy and safety in real-world indoor environments.

The Environmental Protection Agency (EPA) and Center For Disease Control (CDC) still consider Bipolar Ionization a new indoor air quality technology. Subsequently, the EPA has not stated NBPI or other forms of ion-generating air purification technologies to be proven methods of removing airborne SARS-CoV-2 particles (COVID-19).

Airborne COVID Particles Eliminated By Bi-Polar Air Ionization

Safety Considerations When Using Bipolar Ionization

According to ASHRAE Epidemic Task Force. 2020. "Building Readiness, Epidemic Conditions in Place, Bipolar Ionization and Other Emerging Technologies." If you are considering the acquisition of bi-polar ionization equipment, you will want to be sure that the equipment meets UL 2998 standard certification (Environmental Claim Validation Procedure [ECVP] for Zero Ozone Emissions from Air Cleaners), which is intended to validate that no harmful levels of Ozone are produced.

Public health organizations and professionals have long recognized Ozone to impact human health adversely. Prolonged exposure to high Ozone levels has been demonstrated to cause severe respiratory issues. According to the EPA, respiratory problems can include a higher risk of lung infections, lung tissue inflammation, chronic bronchitis, and aggravated asthma symptoms. Therefore when choosing an air purification technology for your facility, consider products that do not produce high levels of Ozone.

Bipolar Ionization Ozone Production

What Is The Difference Between Bipolar Ionization And UVGI?

Ultraviolet Germicidal Irradiation (UVGI), unlike Bipolar Ionization, leverages UV light energy to eliminate airborne pathogens. UVGI air purifiers apply 254 nm UV-C energy to microorganisms damaging their DNA and disrupting the pathogen's ability to replicate. Upper-room UVGI devices create a disinfection zone above a room's occupancy eliminating pathogens that pass through the disinfection zone.

Similar to Bipolar Ionization, UVGI technology can also be installed in HVAC systems and ductwork. For HVAC systems, Induct UVGI devices can enhance the quality of air distributed throughout a facility by eliminating airborne pathogens in "downstream" air as they pass by the UV light in the enclosed area.

However, unlike Bipolar Ionization, UVGI has significantly more research and studies verifying the technology's efficacy. The CDC has provided recommendations for the safe use of UV-C/UVGI technologies in education and workplace environments against SARS-CoV-2. Given the use of UV light, UVGI systems also often have to comply with strict CARB Certification and UL Certification requirements.

Bi-Polar Ionization Vs UV-C Light Fixture

Should You Consider Bipolar Ionizer?

Despite limited testing and studies conducted on Bipolar Ionization, this technology has become a hot-ticket item for many schools, businesses, and medical facilities seeking to make air quality upgrades in their facilities. Influenced by lab testing claims and the rush for HVAC infrastructure improvements from the COVID-19 pandemic, some facilities may have made the wrong choice for their building and community. 

If you're considering an air purification technology for your facility, choose a solution backed by science, testing, demonstrated safety, and supported by industry recommendations. For emerging air quality technologies, it's essential to recognize these key indicators for a technology's true safety and efficacy. 

Modern Office With Bi-Polar Ionization System

Helping You Find The Best Indoor Air Quality Solution

At Sanalife, our helpful team of experts is here to provide you with all the resources needed to make an informed decision when choosing an air quality solution for your business or school. From our range of portable, HVAC Induct, and mounted air purification systems, Sanalife's solutions combine the best-trusted air filtration and active air purification technologies. Choose the innovative solution for your industry today by visiting

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