Ionizer Air Purifiers: Everything You Need to Know

Ionizers make plenty of claims about how well they will clean the air in your room, prevent allergy symptoms, provide “freshness,” or eliminate odors. But what does an ionizer actually do? How does it remove particles from the air, or improve the smell in a room? And do they actually improve your indoor air quality? We will examine what ionizing air purifiers do and their potential negative effects.

What is an ionizer?

Ionizers are also called “ionizer air purifiers,” “ionizing air purifiers,” “air ionizers,” “ion generators” and “ionic air purifiers.” Additionally, there are air purifiers called “electrostatic air purifiers,” or “electrostatic precipitators,” which work similarly to ionizers (we will explain these differences when relevant). For simplicity, we will refer to all these types of ionizing air purifiers as “ionizers.”

Ionizers use high voltage to give an electrical charge (usually negative) to either particles that move through the ionizer, or to molecules in the air. These charged molecules are called ions, and the ions will then stick to particles. In either case, the end result is particles with an electrical charge.

Charged particles are attracted to particles or surfaces with the opposite charge. This causes the particles to clump together, forming larger, heavier particles that settle out of the air onto nearby surfaces. Alternately, particles can be attracted to, and stuck to, charged surfaces like carpet or curtains that have gained a positive charge through static electricity. Electrostatic air purifiers take advantage of this fact by providing a positively charged collector plate that attracts particles. Regular ionizers do not have a plate, so the particles end up on the floor or stuck to the curtains somewhere else in the room.

Ionizers can be made in many different forms. Some are fanless, relying on air currents within the room to carry particles through them. This has the advantage of being very quiet, but it takes a long time for a fanless ionizer to purify all the air in a room. Others use a fan to speed things up. Ionizers can also be combined with other air purification technologies, such as a HEPA filter for removing more particles from the air, or a carbon filter for removing volatile organic compounds (VOCs), odors and other gaseous pollutants. Sometimes the filter is charged, so it acts as the collector plate in an electrostatic purifier. In many hybrid units, the ionizing function is optional and can be turned off independently of the rest of the purifier’s functions.

In the early 2000s the Ionic Breeze ionizing air purifier was sold by Sharper Image in shopping malls across the U.S. It was a new way of using technology to purify air, and for a while many people bought into the hype. But Consumer Reports tested the Ionic Breeze and found it ineffective at purifying air (and later, potentially dangerous because it generated ozone). Sharper Image sued Consumer Reports’ parent company but lost, and the company in turn faced a class action lawsuit before eventually going out of business (although the Sharper Image brand name lives on).

Do ionizers really work?

There are two types of pollutants you need to deal with to improve your indoor air quality: particulate pollutants and gaseous pollutants. To determine if ionizers are effective, we need to address both types.

  • Gaseous pollutants: Ionizers do not remove gaseous pollutants, VOCs or odors from the air. They are designed only to remove particulate pollutants from the air, so they are not effective at all for removing gaseous pollutants. Ionizers can produce ozone as a side effect, and ozone can have an effect on gaseous pollutants (and not necessarily a beneficial one). We will discuss ozone in more detail shortly.
  • Particulate pollutants: An ionizer by itself (not considering any other air purification technologies it may be combined with) is of limited use in removing particulate pollutants from the air. While adding an electrical charge to particles causes them to clump together and precipitate out of the air, the particles end up on the floor or stuck to upholstery, carpets or curtains. This mess needs to be cleaned up, and even with regular cleaning, a high proportion of the particles, including dust, pet allergens, mold spores and other pollutants, gets kicked back into the air by air currents.

Ionizers are not especially efficient anyway. Fanless models clean a relatively small amount of air, and even models with fans have low clean air delivery ratings (CADR). On the plus side, small, fanless models are very quiet and easy to move from room to room.

Ionizers that use an electrostatic collector plate are more efficient—in fact, they are quite good at removing particles from the air. However, this efficiency only lasts as long as the collector plate is clean. As it becomes saturated with particles, efficiency drops drastically. Electrostatic precipitators also draw a lot of electricity.

The process of using an electrical charge to generate ions also creates ozone gas. Ozone can be used to decontaminate and sterilize indoor areas, and is often used for that purpose. However, at effective concentrations, it is very dangerous. Ozone is toxic and is a lung irritant even at low concentrations. It can also react with gaseous pollutants, but there is no way to predict what other chemicals this reaction will create (ozone reacts with some common household pollutants to create formaldehyde, for instance). Generating ozone in your house is a major drawback for ionizers.

Should you use an ionizer?

Given their general lack of effectiveness and the potential hazards of generating ozone in your house, we do not recommend using an ionizing air purifier if someone in your house has asthma or other respiratory problems. The EPA also cautions against generating ozone in your house.

If you choose to use an ionizer anyway, or if you already have one that you do not want to get rid of, here are some tips for using it safely and effectively:

  • Clean the collector plate on electrostatic precipitator models frequently.
  • Clean the area around the ionizer regularly, preferably using a vacuum cleaner with a HEPA filter.
  • If it is a hybrid unit, turn off the ionizing feature if possible.
  • Do not use an ionizer in an enclosed space when someone is present. Either open a window or run the ionizer when no one is home, turning it off whenever anyone is in the room with it.

Better air purifier technology choices

If you want to remove particles such as dust, pet dander, pollen or mold spores from the air in your home, HEPA filters are a decent option, known for their efficiency and track record. However, these filters need to be changed regularly, or they will become clogged with particles and become a source of pollution themselves. If you have problems with gaseous pollutants, including fumes from paint or out-gassing from carpets or furniture, or simply want to get rid of bad smells, a carbon filter will do a good job for the most part. However, carbon filters also need regular changing, and are not effective against particulate pollutants. There are units on the market that contain both HEPA and carbon filters.

Our solution for indoor air pollution, the Molekule air purifier, contains PECO technology, that  goes beyond trapping particles on filters to destroying particulate and gaseous pollutants, so it could be an excellent option for removing pollutants in your home.