Air purifiers vs ionizers: What's the difference?

Air purifiers vs ionizers: Image shows air purifier next to a plant
(Image credit: Getty)

We're delving into everything you need to know around the air purifiers vs ionizers debate and how these could help out in your home. Air pollution and the quality of the air we breathe is a hot topic, but discussions generally focus on the state of the air outside. What about the air inside, in our homes, schools and workplaces?

Indoor air contains allergens like dust, pollen and pet dander, bacteria, viruses and particles released by cosmetics and cleaning products. Many of these particles are known irritants that can exacerbate allergies and asthma but can be eliminated from the air using an air purifier.

Air purifiers capture pollutants, toxins and allergens in the air using a fan and a filter. They are good at what they do and cleanse the air of particulates of various sizes, including coarse particles like pollen and dust, fine particles like pet dander, and ultrafine particles such as viruses.

Air ionizers perform a similar task, except they purify the air in the room by creating negative ions that attach to allergens, which are positively charged, helping impurities settle to the ground. Here, we take a closer look at the difference between air purifiers and ionizers. If you're considering investing in either, we do have a guide to the best air purifiers right now.

Air purifiers vs ionizers

Broadly speaking, air purifiers and ionizers perform the same function — they cleanse the air, removing allergens and pollutants. They can both remove particles measuring a thousand times smaller than a millimeter, but how they do it is very different.

Air purifiers consist of one or more filters and a fan. How do they work? An internal fan pulls room air over the filter. Particles are then captured within the filter's many layers and pleats. Once that process finishes, clean air is recirculated in the room. The Environmental Protection Agency (EPA) says that air purifiers with high-efficiency particulate air (HEPA) filters can hypothetically remove at least 99.97% of airborne particles with a size of 0.3 microns, including dust, pollen, mold and bacteria.

In contrast, air ionizers exploit the chemical properties of ions to remove particles and microbes from the air. Ionizers create negative ions using electricity and discharge them into the air. The negative ions attach to positively charged particles in the room to create a dense particle that is heavy enough to fall to the floor.

The negative ions used by ionizers can stop the growth of viruses, while the ozone produced by the interaction of negative ions and other particles can kill bacteria, fungi, and mold. However, the EPA says air ionizers are relatively ineffective at removing larger particles like dust and pollen, and they are more suited to removing smaller particles such as tobacco smoke and smog, which measure between 0.01 and 0.1 µm/microns.

Air purifiers vs ionizers: Image shows woman petting dog next to an air purifier

(Image credit: Getty)

Air purifiers vs ionizers: how do they affect air quality?

Air purifiers and ionizers use different technology to cleanse the air. While air purifiers remove particles from circulation by trapping them, ionizers simply make them heavy enough to fall to the ground meaning they still need to be cleaned up, and they can easily be disturbed and reintroduced into the air.

Air purifiers also work on a wider range of particles such as large allergens like dust and pollen as well as smaller ones such as pet dander, bacteria, and viruses. This means they are helpful for those suffering from pet allergies, hay fever, and asthma. If you need more, we have a full feature on air purifiers and allergies.

As they remove a much narrower range of particles, air ionizers may not be as good at eliminating the triggers of allergies and asthma. That’s not to say they won’t help, but it’s important to identify what causes the allergy and do your research before investing in an ionizer.

The negative ions associated with ionizers have been identified to positively affect psychological health, productivity, and overall well-being and could help those with seasonal affective disorder (SAD)

However, ionizers indirectly produce ozone – three oxygen particles bound together through the interaction of their negative ions with other particles. Ozone is a known lung irritant, and in some cases, ionizers produce the gas at levels significantly above those thought to be harmful to human health. This could exacerbate existing respiratory conditions, like asthma.

For that reason, it's important to weigh the positive impact an ionizer may have on the level of particles in the air against any damage it could do to your health by producing ozone. In the short term, the EPA says that inhaling small amounts of the gas could lead to throat irritation, chest pain, coughing, shortness of breath, or difficulty breathing. Long-term effects include worsening asthma symptoms, a decrease in lung function, and lung inflammation.

Air purifiers vs ionizers: Image shows pet hair and lead on the floor

(Image credit: Getty)

Air purifiers vs ionizers: which is right for you?

Whether you choose an air purifier or an ionizer will depend on what you need. Air purifiers are well suited to removing pollen, pet dander, and other particulates from the air, so they are ideal for those with allergies and asthma who want to remove the trigger of their symptoms.

How effectively they do this depends on the type of purifier and the filter they use. HEPA filters, with their dense network of superfine fiberglass fibers that are thinner than a strand of human hair, remove particles as small as 0.3µm/microns, around the size of some cat and dust mites allergens. It's worth noting that air purifiers are largely safe for pets themselves, although you should still check basic safety measures if you have a pet at home.

Ionizers are better at removing smaller molecules like bacteria and viruses, so they may not benefit those suffering from allergies or asthma. Ionizers also don’t remove the particles from circulation. Instead, they charge them so they stick to something else. Unless you are constantly cleaning the hard and soft surfaces in your home, it becomes difficult to remove the particles that have dropped to the floor. 

Kerry Taylor-Smith

Kerry is a freelance writer and editor, specializing in science and health-related topics. Her work has appeared in many scientific and medical magazines and websites, including Forward, Patient, NetDoctor, YourWeather, the AZO portfolio, and NS Media titles.

Kerry’s articles cover a wide range of topics including astronomy, nanotechnology, physics, medical devices, pharmaceuticals and mental health, but she has a particular interest in environmental science, cleantech and climate change. 

​​​Kerry is NCTJ trained, and has a degree Natural Sciences from the University of Bath where she studied a range of topics, including chemistry, biology, and environmental sciences.