In this modern era of the tech revolution, there are plenty of sophisticated methods out there for air filtration. Not all of them are equally effective; some are not suitable for residential use.
In this article, we discuss the 8 types of air cleaning technologies used in consumer air purifiers including their advantages and disadvantages.
It is good to know that there are two types of indoor air pollutants: Particulates and Gaseous. Particulate pollutants are also known as Particulate Matters (PM), and by their sizes, they are categorized in various manners such as PM1, PM2.5, and PM10. Dust, pollen, mold spores, smoke residue, airborne viruses, and bacteria fall into this category.
Common indoor gaseous pollutants are carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, radon, volatile organic compounds (VOCs), and Formaldehyde.
Please read our article on indoor air pollutants and their sources.
Conventional Air Filtration Methods:
Air filtration methods fall into two major categories: mechanical and electronic. Mechanical filtrations are safe and effective, while electronic filtrations are less efficient. Here are the 8 types of air filtration technologies that are used in modern air purifiers:
- Fibrous Media Filter
- Adsorbent Media Filter
- Ionizers
- Ultraviolet Germicidal Irradiation (UVGI)
- Photocatalytic Oxidation (PCO)
- Electrostatic precipitation (ESP)
- Plasma
- Intentional Ozone Generator
1. Fibrous Media Filter
Targeted Air Pollutants: Particles
Type: Mechanical
Working Principle: When the air passes, the dense fibrous media filter traps particles in its mesh type structures. The HEPA filter is the most popular in this category.
Advantages:
- High-efficiency fibrous filters are effective in trapping tiny airborne particles.
- This method is the safest among air cleaning technologies.
Disadvantages:
- High operating cost as the filter needs to be replaced regularly.
- Pollutants are deposited in the filter often create secondary air pollution.
Test Standards:
ANSI/ASHRAE Standard 52.2 (MERV)
ISO 16890 (ePM)
ISO 29463 (HEPA)
EN 1822
2. Adsorbent Media Filter
Targeted Air Pollutants: Gas, VOCs
Type: Mechanical
Working Principle: Adsorbant media filter neutralizes odors, VOCs, and gases by chemical adsorption. Activated carbon is widely used as adsorbent media in air purifiers.
Advantages:
- Absorb multiple ranges of gases and volatile organic compounds (VOCs).
- Reduce various household odors.
Disadvantages:
- The filter saturates fast.
- Higher filter replacement cost.
- Effectiveness varies on gas types.
Test Standards:
ANSI/ASHRAE Standard 145.1
3. Ionizers (Ion generators)
Targeted Air Pollutants: Particles
Type: Electronic
Working Principle: Ionizers release negative ions, which are attached to airborne particles and make them heavier. Eventually, the pollutants are collected into charged plates, or they fall to the ground.
Advantages:
- It can operate at low power.
- Low maintenance required.
Disadvantages:
- Often produces ozone.
- Slow air filtration process.
Test Standards:
AHAM AC-1 for CADR
4. Ultraviolet Germicidal Irradiation (UVGI)
Targeted Air Pollutants: Microorganisms
Type: Electronic
Working Principle: UVGI applies Ultraviolet (UV-C) light to destroy airborne microbes such as dust mites, molds, bacteria, and viruses. Also known as UV air sanitizer.
Advantages:
- Effective in deactivating germs.
- Easy to operate and maintain.
Disadvantages:
- It might produce ozone.
- Uncovered UV-C ray is harmful to human eyes.
- It kills microbes but doesn’t remove them from the air.
Test Standards:
ANSI/ASHRAE Standard 185.1
ANSI/ASHRAE Standard 185.2
5. Photocatalytic Oxidation (PCO)
Targeted Air Pollutants: Gas, VOCs
Type: Electronic
Working Principle: The PCO process transforms gaseous pollutants into harmless byproducts such as water and carbon dioxide. The filtration is done by an oxidation process using titanium oxide (TiO2) as a catalyst and UV light as an igniter.
Advantages:
- PCO neutralizes a wide variety of gaseous pollutants.
- Low energy permanent UV light is used.
Disadvantages:
- Often produce formaldehyde and ozone as chemical byproducts.
- Slow filtration process.
Test Standards:
No specific standard
6. Electrostatic precipitation (ESP)
Targeted Air Pollutants: Particles
Type: Electronic
Working Principle: It ionizes the air by corona discharge process and then collects the particles on its electrically charged plates.
Advantages:
- It can remove particles with high efficiency.
- Low maintenance required.
Disadvantages:
- Often generates chemical byproducts such as ozone and nitrogen oxide.
- Higher energy cost.
Test Standards:
UL 867 for ESP air purifiers
7. Plasma
Targeted Air Pollutants: Gas, VOCs
Type: Electronic
Working Principle: Transform gaseous pollutants by breaking their chemical bond using electrical arcs.
Advantages:
- Plasma has high filtration efficiency.
- It can be combining with other air filtration methods.
Disadvantages:
- Often produces chemical byproducts such as carbon monoxide, ozone, and some organic gases.
- Cannot remove particle pollutants.
Test Standards:
No specific standard
8. Intentional ozone generator
Targeted Air Pollutants: Gas, VOCs
Type: Electronic
Working Principle: Deliberately produces ozone using UV light or corona discharge to break down gases and volatile organic compounds.
Advantages:
- It neutralizes all kinds of indoor gases.
Disadvantages:
- Not suitable for residential spaces.
- Ozone is harmful to home appliances.
Test Standards:
No specific standard
Primary Source of data: Residential Air Cleaners: A Technical Summary, 3rd edition
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