February 7, 2023
Last Updated On:
February 7, 2023

Active vs. Passive Air Purification: What's The Difference?

Learn the unique differences between active and passive air purification methods to help you determine the best option for your facility.

Last Updated On:
February 7, 2023

Air purification is essential for maintaining a clean and healthy indoor environment. However, not all air purification methods are created equal. There are two main types of air purification technologies: active and passive air purification. This article will compare the differences between active and passive air purification methods to help you determine the best option for your facility.

What Is Passive Air Purification?

Passive air purification, commonly referred to as mechanical air filtration, relies on drawing in air through an air purification system to either capture or eliminate airborne pollutants. Passive air purification is often considered the "economical" or "traditional" option for improving indoor air quality. However, passive air purification systems can only remove or capture airborne contaminants that pass through the system. Passive air purifiers commonly lack the capability of proactively cleaning the air throughout an entire room or space because the air must pass through the system to get cleaned.

Portable Air Purifier With High CFM Fan

Types of Passive Air Purification Technology

Mechanical Air Filtration: HEPA & MERV Filters

Mechanical air filtration systems are a type of passive air purification technology that works by trapping airborne contaminants in filters as air is drawn through the filtration media. These systems typically utilize the "gold standard" of passive air filtration media, including HEPA (High-Efficiency Particulate Air) or MERV (Minimum Efficiency Reporting Value) rated filters to capture pollutants such as dust, pollen, pet dander, and other allergens.

A mechanical air filtration system's effectiveness largely depends on the filters' rating and high-CFM (Cubic Feet per Minute) fans within the system. True HEPA filters are considered highly efficient, as they can capture particles as small as 0.3 microns with a minimum efficiency of 99.97%. On the other hand, MERV-rated filters can vary in efficiency, with higher MERV ratings indicating better filtration performance. MERV ratings can range from 1 to 20, with higher ratings capable of capturing smaller particles, restricting airflow, and causing HVAC pressure drops.

While mechanical air filtration systems can effectively remove particles from the air, it's important to note that they are limited in reducing airborne concentrations of pathogenic particulate. Commercial-grade air purifiers combine mechanical filtration with other technologies, such as UV-C, Ionization, or PCO Technology, to address the full spectrum of indoor air pollutants.

How UVGI Air Purification Works
How Upper-Room UVGI Air Purifiers Create A Disinfection Zone (Source: CDC 2019)

Ultraviolet Germicidal Irradiation (UVGI):

UVGI (Ultraviolet Germicidal Irradiation) air purification systems are designed to improve indoor air quality by using UV-C light to inactivate or eliminate organic contaminants. Sterilization in UVGI air purifiers works by drawing air into a sterilization chamber using high-CFM fans, exposing the air to the UV-C light. This light can penetrate and disrupt the DNA or RNA of microorganisms, including bacteria, viruses, and mold, rendering them inactive or eliminating them altogether.

However, it is essential to note that while UVGI air purifiers effectively remove certain types of pollutants, such as bacteria, viruses, and mold, they do not address the entire spectrum of indoor air pollutants. This means that smaller particles, such as dust, pollen, and smoke, as well as gaseous pollutants, such as volatile organic compounds (VOCs) and chemicals, may still be present in the air. Therefore, UVGI air purifiers should be used with other air cleaning technologies to achieve optimal indoor air quality.

How PCO Technology Air Purification Works
How Photocatalytic Oxidation Air Purifiers Destroys Pollutants (Source: Nature Communications)

Photocatalytic Oxidation (PCO) Technology:

PCO technology-based air purifiers use light energy to activate a catalytic process that breaks down pollutants and bacteria in the air. The UV light energy emitted by a UV lamp or high-energy UV LEDs is absorbed by a photocatalyst triggering a chemical reaction that destroys pollutants and bacteria within the catalytic chamber.

Traditional PCO technology is often mistaken as an active form of air purification. However, most portable air purifiers or HVAC induct solutions that use PCO technology rely on air passing through the system to reduce airborne pathogens. Most standalone air purifiers with PCO technology are only as effective as their CFM rating to draw in the surrounding air to "clean" and "purify" the air eliminating airborne pollutants.

What Is Active Air Purification?

Active air purification, often associated with electronic air purification technologies, is designed to proactively improve indoor air quality throughout an entire room or space. Unlike passive air purification systems, active air purification can reduce airborne contaminants beyond what passives through the system itself. Popular methods of active air purification often distribute molecules or ions throughout a space to attach to, reduce, or eliminate airborne pathogens.

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Types of Active Air Purification Technology

Bi-Polar Ionization Technology:

A commonly used "active" air quality technology in commercial environments is Bi-Polar Ionization. Bi-Polar Ionization attempts to purify the air throughout an entire space by injecting positive and negative ions into the air. The Ionization of the air creates an electrical charge on airborne particulate, causing it to fall out of the air onto surfaces. The technology works similarly to Corona Discharge and can be achieved through two methods: Corona Discharge and Brush Discharge.

The Corona Discharge method uses high-voltage electricity, a pointy conductive needle, and an electrical wire to generate a strong electrical field to ionize the surrounding air. This method is commonly used in electronic air purification systems placed within HVAC ductwork, often called "Needle-Point Ionization."

On the other hand, the Brush Discharge method is typically used in portable air purifiers and relies on a lower voltage to ionize the air. The electrical field is generated between two electrodes, one flat and one rounded. While less effective for HVAC system installation, Brush Discharge systems can still ionize lower volumes of air.

How Bi-Polar Ionization Works?
How Air Ionization Works In Active Air Purification (Source: Modern Castle)

While Bi-Polar Ionization can effectively reduce airborne contaminants, it does not solve indoor air quality issues. These charged ions cause particulate to fall out of the air and do not physically eliminate the contaminants. In indoor environments, occupant activity can resuspend the airborne particles and keep them in the air, leading to the potential for inhalation. Moreover, the ions can stick to surfaces and lung tissue, increasing the potential for particulate to be deposited in the lungs.

It's worth noting that Bi-Polar Ionization systems often produce some level of Ozone, which is known to have adverse health effects. High ozone concentrations can also react with volatile organic compounds (VOCs) emitted from cleaning products and building materials to create airborne toxins and irritants. High VOC concentrations can lead to additional health risks without proper passive air filtration or elimination.

The Formation of Ozone

Intentional Ozone Generation:

A commonly used "active" air quality technology in industrial settings is "Intentional" Ozone Generation. Ozone Generation is an air purification technology that creates Ozone (O3) to remove airborne contaminants. The process works by using Ozone's highly reactive composition of three Oxygen atoms, which allows it to bond with airborne organic pollutants and oxidize them, effectively neutralizing the contaminants. Two standard methods of producing Ozone are Silent Corona Discharge and Ultraviolet Radiation.

Silent Corona Discharge is a type of Ozone generation that uses an electrical charge to split apart stable Oxygen (O2) molecules. When air is passed through the generator, the resulting unstable single Oxygen atoms bond with other O2 molecules to form Ozone (O3). This method is known to be effective in producing Ozone, making it a popular choice for many Ozone generators.

Ultraviolet Radiation is another way of generating Ozone. It uses ultraviolet light (similar to the Sun) to split apart stable Oxygen (O2) molecules. Although it can produce Ozone, when compared to Silent Corona Discharge, Ultraviolet Radiation is less effective in splitting O2 molecules into single unstable Oxygen atoms.

How Ozone Generation Works
How Ozone Generation Occurs With Corona Discharge And Ultraviolet Light (Source: Ozone Solutions)

Ozone is a popular air purification method utilized in buildings that have experienced fire, smoke, or flood damage. It effectively binds to odor molecules and neutralizes bacteria, mold, and viruses, including COVID-19. However, ozone generators can also pose a health risk, as exposure to high ozone levels can result in severe respiratory issues, according to the U.S. Environmental Protection Agency (EPA). These issues include lung tissue inflammation, exacerbated asthma, chronic bronchitis, and a higher risk of lung infections.

It is important to note that Ozone generators have not been approved for use in occupied indoor environments by U.S. federal agencies. Regulations around air purifiers are stringent in California, where the California Air Resources Board (CARB) has established guidelines to ensure that certified air purifiers do not produce harmful ozone levels during operation. This helps to minimize the potential health risks associated with using Ozone generators.

ActivePure Technology Proprietary Cell

ActivePure Technology:

One of the most popular active air purification technologies is ActivePure Technology. ActivePure, often referred to as Advanced Active Photocatalytic Oxidation (AAPC), is based on Radiant Catalytic Ionization (RCI). ActivePure uses the production of energy in the UV-C range (irradiation), striking a titanium dioxide-based proprietary photocatalyst forming "air scrubbing molecules."

These "air scrubbing molecules," including oxidizers (hydroxyl radicals, superoxide, hydroxide, and hydrogen peroxide), are distributed throughout an entire space causing the decomposition of viruses, bacteria, mold, fungi, and volatile organic compounds (VOCs) through continuous oxidation, resulting in decomposition byproducts, including CO2 and water in the air.​

ActivePure air purifiers, whether standalone portable devices or HVAC induct installed units, proactively seek and reduce airborne pathogens throughout an entire space. No matter the indoor environment ActivePure's scalable air quality solutions can operate 24/7 to clean and purify the air continuously, providing superior protection against indoor air pollutants.

Facility Managers Planning HVAC System Install

Active or Passive Air Purification Technology: What Should I Choose?

Luckily in 2023, whether you are seeking an indoor air quality solution for your business, commercial building, or school district, there are plenty of options for effective air purification. For those looking for a passive air purification solution, there is no better choice than the "gold standard" in mechanical air filtration, such as HEPA and MERV filters. Between portable air purifiers and HVAC filter upgrades, these filters can effectively reduce airborne pollutants.

However, if your facility is looking for a long-term air quality solution to combat airborne pathogen concentrations and transform indoor environments into healthier spaces, consider ActivePure Technology. ActivePure air quality solutions are custom engineered for every facility for maximum coverage. Each solution designed by a team of experts can also reduce your building's energy costs and help your organization achieve its sustainability and ESG goals.

Over the last several years, ActivePure has rigorously performed independent laboratory and real-world testing to prove the technology's safety and efficacy. That way, every facility that implements ActivePure can trust their choice and ensure the air inside their building remains clean and healthy for everyone. No matter what air purification technology you choose, understanding the differences between popular active and passive air purification technologies will help you make the best and most informed decision for your facility.

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