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Air Purifiers vs Ionizers: What’s the Difference?

Last updated April 12, 2022

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Author
Author avatar Jeanne Yacoubou

Jeanne is our newest air quality aficionado/writer. Still shocked by the arrival of Summer 2021 wildfire smoke from California to her Maryland (East Coast) home, she’s forever indebted to her HEPA filter-equipped air purifier.

Our verdict:

Air purifiers are significantly different from air ionizers in how they work and what they do. Air purifiers equipped with specialized filters permanently remove odors and contaminants from your indoor air by trapping them as air flows through the filters. Air purifiers then release cleaner air to your living space using a fan. On the other hand, through electrical charging, air ionizers temporarily reposition some pollutants from the air onto surfaces. They may become airborne again. There are no negative health outcomes associated with running an air purifier in your home. By contrast, air ionizers may produce ozone and other toxic gases, all of which are harmful to humans and pets.

From looks alone, air purifiers and ionizers have a lot in common. Both are often portable, cylindrical, or box-like with buttons or a dial and air vents.

But appearances can be deceiving.

Technically speaking, what goes on inside air purifiers vs ionizers is very different.

Through specialized filters, air purifiers (also called air cleaners) trap airborne contaminants of all shapes and sizes removing them completely from your home. 


Here’s a size comparison chart of common indoor air contaminants. (For context: a human hair is ~75 microns wide.)

Air PollutantSize Range (micron)
Smoke (natural source)0.01-0.1
Bacteria0.3-60
Household Dust0.05-100
Mold3-12
Pollen10-1,000

Note: Some particle pollution and microorganisms, including SARS-CoV-2, the virus that causes Covid-19, may be smaller than 0.1 microns. The United States Environmental Protection Agency (EPA) advises that air purifiers — by themselves — do not protect against this virus.

By contrast, air ionizers (also called ionic air purifiers, ion generators, or simply ionizers) don’t trap anything. 

Ionizers produce electrically charged particles that attract and attach to mid-sized air contaminants such as some bacteria, dust, and mold

The heavier charged ion-pollutant clusters fall onto surfaces including furniture and floors…or even you

Homeowners may be able to wipe, sweep, or vacuum them up before they lose their charge, detach from each other, and go airborne again. 

Beware: The very act of cleaning may cause disruption, liberating dust bunnies and other nasties to reenter your airspace.

How Do They Work?

If you take a peek inside each unit, you’d see very different parts. This contrast explains their unique modes of action.  

Air Purifiers

There are several different types of air purifiers on the market today. The best air cleaners permanently remove airborne contaminants by trapping them in filters.

Activated Carbon, Zeolite, Metal Oxide Filter 

The first major filter that incoming air encounters as it is pulled into the device is often made of activated carbon (activated charcoal, biochar), zeolite, metal oxides (earth minerals), or a combination of them.

Through the processes of physical adsorption and chemisorption, this filter captures many gaseous pollutants including:

  • Volatile organic compounds (VOCs)
  • Tobacco and marijuana smoke
  • Vaping gases
  • Ozone
  • Carbon monoxide 
  • Nitrogen dioxide

HEPA Filter

Next, air moves through a high-efficiency particulate air (HEPA) filter. Through the four mechanical processes listed below, HEPA filters entrap particle pollution (particulate matter, PM):

  • Sieving (straining)
  • Inertial impaction
  • Interception
  • Diffusion 

By definition, HEPA filters ensnare ~98% of particulates as small as 0.3 microns. Some HEPAs, under certain conditions, may also trap ultrafine particulate matter (PM0.1). 

Air purifiers then send clean air out to your living areas via a fan.

Health Benefits of Air Purifiers

There is abundant scientific evidence that high-quality air purifiers do wonders for human health. For example:

  • Improved cardiorespiratory capacity
  • Decreased blood pressure
  • Reduced oxidative stress
  • Lowered systemic inflammation
  • Enhanced lung function

Air Ionizers

Have you experienced static cling with clothes fresh out of the dryer? Or, in winter, you may have gotten a slight electric shock or seen a spark when touching certain fabrics.

Air ionizers work on the same principle of static electricity: electrostatic attraction of unlike (positive and negative) charges.

Air Ionizers Based on Corona Discharge

Ionizers based on corona discharge apply a high-voltage (5K-20K) electrical current to a metal prong or needle — functioning like an antenna — within an electric field. In the presence of air, the electric stream creates ions (charged particles) out of the neutral molecules in the air including oxygen, nitrogen, and water. Hundreds of thousands of different types of ions are formed. These ions enter the airspace around the device, usually without the aid of a blower fan.

Air Ionizers Based on Electrostatic Precipitation

Some air ionizers operate as electrostatic precipitators. As air flows over precipitation plates due to an ionic wind moving in one direction, air contaminants become charged and deposit on the plates.

Types of Air Ionizers

Negative ion air ionizers are the most popular ones on the market today. These produce only negative ions and are called unipolar ionizers.

Under development are plant-based negative ion air ionizers operating under pulsed electric fields (PEF) conditions and producing millions of ions per cubic meter.

Also commercially available are bipolar ionizers, producing both negative and positive ions.

Benefits of Air Ionizers

Despite the good press, negative ions receive about positive health effects, there is no conclusive scientific evidence to support these claims. This applies to both physical and mental health

Drawbacks of Air Ionizers

Although there may be a temporary but significant reduction in certain types of air contaminants from the use of air ionizers, the production of ozone and other toxic gases from the normal operation of these devices often results in no overall change or even an increase in certain air pollutants such as ozone, oxygenated volatile organic chemicals (VOCs) and toluene

Which is Better for You: Air Purifiers vs Ionizers? 

If you’re looking for a device that permanently removes air contaminants from your home with no bad side effects, air purifiers equipped with HEPA and activated carbon, zeolite, or metal oxide filters win this one hands down.

The indirect creation of ozone and other gases by air ionizers can actually harm your health.

FAQs: Air Purifiers vs Ionizers

Hopefully, this article on air purifiers vs ionizers tells you everything you need to know to choose the better one to meet your needs. In case you still have questions, these FAQs may help.

How hazardous is ozone?

In large concentrations, ozone is extremely hazardous to health. It is a potent lung irritant. Ozone may also worsen asthma and allergies.

This is true if you’re breathing ozone in a smoggy city. But since air pollution travels, even suburbanites and rural dwellers must be careful. 

It’s also true that ozone produced as a byproduct during the normal operation of an air ionizer is hazardous to health. Ionic air cleaners may mistakenly be dubbed ozone generators, which directly create significant amounts of ozone.

Note that different brands of ionizers produce varying amounts of ozone. Unfortunately, it may be difficult to find trustworthy test results about specific brands. 

In an enclosed, non-ventilated room, running an ionizer for a long time will produce more ozone. It takes time for ozone to break down. 

So, if you’re using an ionizer, treat it like a bona fide ozone generator. Stay out of the area for several hours to prevent ozone exposure.

Why do some air purifiers have ionizers?

Based on the meta-analysis of multiple research studies testing both negative and positive ions, air ionizers may reduce some indoor air pollutants, but not permanently remove them from air. There is no conclusive evidence that using ionizers results in positive health outcomes.

The only study we’ve located examining air purifier-ionizer combo devices shows an increased cardiovascular health risk associated with the ionizer only.

So, we must conclude that companies marketing air purifier-air ionizer devices are attempting to profit from the heightened interest in ionizers as protective against airborne microbes such as SARS-CoV-2. 

To date, there is no scientific evidence that proves air ionizers kill the virus that causes Covid-19, although there is experimental support for high-powered ozone generators as disinfectants for some airborne viruses. However, air purifiers with HEPA filters are recommended by experts as an important tool in controlling airborne viruses.

Do Air Ionizers Remove Odor?

Air ionizers do not remove odors from indoor air. At best, they temporarily disable some air contaminants which may go airborne again if not removed without causing further air disruption.

On the other hand, activated carbon, metal oxide, or zeolite filters — or some hybrid — in many air purifiers can permanently remove odors from your home.