White ionizing air purifier on a desk with a person using a laptop in the background.
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If you’re shopping for an air purifier, you’ll likely encounter ionic air purifiers. These work differently than the ones with high-efficiency particulate air (HEPA) filters, which have sort of become the “standard” air purifier. So are ionic air purifiers better?

What Is an Ionic Air Purifier?

Ionic air purifiers are air cleaners that help your remove or reduce ultrafine contaminants from the surrounding air. Also called ionizers or ion generators, the ionic air purifiers release a negative ion charge that attaches to the pollutants in the air and leads them to stick to a nearby surface. Some ionic air purifiers also come with a positively charged collector to attract the negatively charged pollutants.

Although ionic air purifiers are typically standalone units, some manufacturers have also started including air ionizers as a part of standard air purifiers with a HEPA filter. In such an air purifier, the air ionizer function is optional, and you can choose to switch it on or keep it off.

What Is a HEPA Air Purifier?

Coway AirMega 400

HEPA air purifiers are the most common consumer-grade air purifiers on the market. As their name suggests, they rely on HEPA filters that they pass air through. Fiberglass or polypropylene filters can theoretically remove all particles of 0.3 microns or more.

Air purifiers with a HEPA filter sometimes include additional filters like a prefilter, an activated carbon filter, or an ultraviolet filter. As mentioned previously, they may also feature an air ionizer.

Ionic vs. HEPA: Which Is Better at Cleaning the Air?

Both ionic and HEPA air purifiers clean the surrounding air but use different technologies. While HEPA purifiers trap contaminants in their filters and effectively remove them from the air, ionic air purifiers simply make them stick to various surfaces in the room, such as walls, floors, drapes, tabletops, and even people. These surfaces need to be cleaned regularly to remove the pollutants; otherwise, any disturbance can cause them to re-enter the air.

Additionally, the United States Environmental Protection Agency (EPA) says that while ionic air purifiers may remove smaller particles, like the ones in cigarette smoke or smog, they may not effectively remove larger particles like pollen and house dust allergens. Ionizers also cannot remove gases and odors.

On the other hand, HEPA purifiers can theoretically filter almost all particles with a size of at least 0.3 microns. Such particles include dust, pollen, mold spores, mildew, pet dander, dust mites, soot, and many airborne pathogens. Unfortunately, like ionic air purifiers, HEPA filters can’t clean gases or odors. However, many air purifier manufacturers include an activated carbon filter with the HEPA filter to remove odors and gaseous pollutants, including volatile organic compounds (VOCs).

You might see claims on the internet suggesting that negative ions released by ionic air purifiers provide some health benefits, particularly in your mood, by fixing a so-called “ion imbalance.” But EPA notes that no controlled studies have confirmed this. Plus, research conducted to look at various studies around air purifiers by Health Canada had a similar conclusion.

Ionic air purifiers as a side effect also produce ozone in the surrounding air. Ozone is a lung irritant, and its inhalation can cause throat irritation, chest pain, coughing, and shortness of breath. While some ionic air purifiers claim to produce zero ozone or below the 0.05 ppm standard set by FDA, research by California Air Resources Board (CARB) has noted that the ozone generation by some ionizers could reach unhealthy levels (PDF) in more realistic conditions compared to the lab conditions in which they are typically tested. That said, CARB maintains a list of air cleaners that have been tested to emit little or no ozone.

HEPA purifiers have no such health concerns but require timely replacement of filters to ensure efficient operation, which adds to their overall cost. Their fan noise at higher settings can also be disruptive. In contrast, most ionic air purifiers work silently and have no filters to replace. As a result, they are cheaper to operate.

Another vital detail to remember about both ionic and HEPA air purifiers is their clear air delivery rate (CADR), a metric used to calculate the efficiency of an air purifier. Most ionic air purifiers have a CADR rate between 0 to 50 cubic feet per minute (CFM), which is quite inferior to the CADR of the best HEPA purifiers. Purifiers with higher ion generation powers could theoretically result in better CADR, but they would also result in unacceptable ozone levels.

What About Electrostatic Precipitators?

Avari 600
Avari Air

Electrostatic precipitators are filterless air cleaners that are also sometimes referred to as ionic air purifiers. But they aren’t technically ionic air purifiers as they don’t release ions in the air. Instead, they rely on electrical charges.

Electrostatic precipitators have two plates—one with a positive charge and the other with a negative charge. When the polluted air circulates through an electrostatic precipitator, the particulate matter passes over the negatively charged plate and gains a negative charge. These charged particles then pass over the positively charged plate (collector plate) and stick to it. As a result, cleaner air exits the purifier, leaving behind contaminants attached to the collector plate.

Unfortunately, while the process of electrostatic precipitators sounds great in theory, it isn’t very efficient in reality. These purifiers don’t capture many particles and often let pollutants pass through them. Additionally, they are only effective when the collector plate is clean. As it gets dirty, the efficiency of the purifier drops. Finally, electrostatic precipitators are known for high power usage.

Which Is Right for You?

Both ionic air purifiers and standard air purifiers with HEPA filters have advantages and disadvantages. But the benefits of HEPA purifiers greatly outweigh their drawbacks. Unfortunately, you can’t necessarily say the same thing about ionic air purifiers. Also, many of the supposed health benefits associated with ionic air purifiers haven’t been widely tested. So if you are still inclined to opt for an ionic air purifier, it’s better to go for one with a built-in HEPA filter than a standalone unit. That way, you get the best of both worlds.

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Profile Photo for Gaurav Shukla Gaurav Shukla
Gaurav Shukla is a technology journalist with over a decade’s experience reporting and writing about consumer technology. His work has appeared in Android Police, XDA Developers, and NDTV Gadgets 360.
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