There’s probably never been a time where we are more concerned about what’s in the air and drifting around our homes. If you are looking into air purifiers, whether it’s to keep allergens at bay, combat smoke and pollution that might be in the air, or just to have cleaner air in your home, you may have seen the term ionizer when it comes to air purifiers. What exactly does this term mean? Is it important to have in an air purifier? And what does it do?

To understand the term ionizing, we first need to understand ions and their presence in our air. An ion is an atom or a molecule with an electric charge; positively charged ions are called cations and negatively charged ions are called anions. (No, there won’t be a quiz.)

Some air purifiers (read our article on the best models) also have the ability to ionize or charge particles in the air, and will often give those molecules a negative charge. So why would you want to do this? The Environmental Protection Agency (EPA) explains it this way: “Ion generators act by charging the particles in a room so that they are attracted to walls, floors, tabletops, draperies, occupants, etc.”

In essence, if these particles aren’t floating around the room because they’ve fallen to a tabletop, you’re less likely to inhale them. Of course, wiping the table can rerelease the molecules into the air, so some ionizing air purifiers have a collector to attract the charged particles into the unit, usually by activating the opposite (or positive) charge.

The EPA further suggests that “while ion generators may remove small particles (e.g., those in tobacco smoke) from the indoor air, they do not remove gases or odors, and may be relatively ineffective in removing large particles such as pollen and house dust allergens.”

You may also see ionizers combined with other air purification technology like HEPA filters, which trap those particles and prevent their rerelease. Sometimes the filter can be charged, so it acts as an attractant for those wayward particles.

In many cases, using an indoor air ionizer produces ozone, which can be an irritant for some people with lung conditions like asthma. The EPA says: “There is even greater concern with the direct, and purposeful introduction of a lung irritant into indoor air. There is no difference, despite some marketers’ claims, between ozone in smog outdoors and ozone produced by these devices. Under certain use condition, ion generators and other ozone-generating air cleaners can produce levels of this lung irritant significantly above levels thought harmful to human health. A small percentage of air cleaners that claim a health benefit may be regulated by the Food and Drug Administration as a medical device. The FDA has set a limit of 0.05 parts per million of ozone for medical devices. Although ozone can be used in reducing odors and pollutants in unoccupied spaces (such as removing smoke odors from homes involved in fires), the levels needed to achieve this are above those generally thought to be safe for humans.”

The bottom line is that if you have health concerns, you should check with a doctor to see if the benefits of removing harmful pollutants by ionizing outweighs the concerns about introducing ozone into your home.

While we could start going through reams of medical studies and journals to debate the effectiveness of using ionization to combat viruses, the truth is that the jury is still out. There may be some benefits to this type of technology, but there’s very little in the way of actual scientific proof in this area (read our article about whether air purifiers can combat coronavirus).

If you’re looking for cleaner air inside your home, an air purifier probably can’t hurt. If you have a compromised immune system or lung issues, an ionizing air purifier might not be the best option. It always pays to seek credible medical advice when your health is at stake.