Under the Hood of Car Air Purifiers and Ionizers

Close-up of automotive air filter
Photo ephemera / Moment / Getty

Years of accumulated odors from food, smoke, and driving by that smelly paper factory every day on the way to work might leave you pining for the “new car smell” of your youth but that’s one genie you just can’t put back in the bottle. But that doesn’t mean you can’t turn back the tide of bad odors. While your new car smell may be gone, you can use a number of different methods, including air fresheners, odor-absorbers, and car air purifiers and ionizers to roll back the clock to the halcyon days before your car stunk so bad.

The efficacy of different methods of sweetening a car’s smell vary from poor to pretty good, but it all depends on what you expect going in. Some low tech options, like soaking up odors with baking soda or charcoal, are pretty basic. The odors get absorbed, and that’s that. And if the source of the bad smell isn’t dealt with first, then you could fill your entire car with charcoal briquettes and do absolutely no good whatsoever.

Other options, like air fresheners, can leave your car smelling rosy (or even vaguely new-car-smelly, if you like), but they only mask the vile odor underneath. If you don’t take care of the source of the bad smell, and then do something to mitigate it, chances are good that throwing in an air freshener will just result in a car that smells like a pine fresh dumpster fire.

Other options, like air purifiers, filters, and ionizers, are a little more technical.

What is an Air Ionizer?

Air ionizers are also called negative ion generators because they use electricity to ionize air molecules. That basically just means that they take neutrally-charged molecules and impart them with a negative electric charge.

Home air purifiers sometimes include built-in ionizers, but automotive air ionizers are typically standalone units that only generate negative ions without any filtering function.

How Do Car Ionizers Work?

The concept behind air ionizers is that the device confers a negative electric charge to airborne particles, including pollen, germs, and various other impurities. These anions are then attracted to surfaces so that they are no longer airborne.

Some air ionizers include a built-in earthed surface to collect impurities, while others rely on the particles getting stuck to surfaces where they can be wiped up or vacuumed at a later time.

Do Car Air Ionizers Work?

While there is no question as to whether car air ionizers function as intended, the jury is out on whether or not there is any real benefit. The issue is that ionizers do not perform up to the same standards as other devices that have a similar purpose, like HEPA filters.

In fact, Consumer Reports famously gave a failing grade to a Sharper Image air ionizer in a 2003 report. The Sharper Image sued Consumer’s Union, the publisher of Consumer Reports, but the lawsuit was not successful. When The Sharper Image failed to disprove Consumer Reports’ statements, the company was even ordered to pay legal expenses.

That isn’t to say that air ionizers don’t work at all. Ionizers have been employed to great effect in a number of situations where they eliminated or reduced the instances of airborne infections. In one instance, the National Health Service in the United Kingdom found that instances of airborne acinetobacter infections fell to zero after ionizers were installed.

The bottom line is that ionizers aren’t magic panaceas, but they may help in conjunction with other methods of removing bad smells.

What is a Car Air Purifier?

Car air purifiers are similar to home air purifiers, but they are much smaller, run on 12 volts, and usually aren’t as effective. At a basic level, they pull in air from the cabin of your car, pass it through a filter or series of filters, and return “purified” air to the cabin.

Do Car Air Purifiers Work?

Like home air purifiers, car air purifiers rely on filters to work, so different models can have drastically different effects. As an example, we’ll look at Philips GoPure, which includes multiple filters and is pretty robust as car air purifiers go.

The GoPure is a three-stage filter, which means it filters in three discrete stages:

  1. Pre-filter, which captures large particles, like pet dander and human hair.
  2. HEPA filter, which filters small particles like dust, pollen, and germs.
  3. HESA filter, which helps deal with odors from smoke, solvents, and other nasty things.

Some car air purifiers have fewer filtering stages, while others may have more. The key is that a car air purifier needs to have one or more filters—preferably removable—to capture particles and impurities from the air.

In order to function, a car air purifier also needs to include some method to pull in air, push it through the filters, and return it to the cabin. For instance, the GoPure has a three-speed fan that allows the user to adjust the flow of air through the device.

Do Car Air Purifiers Work?

As with home air purifiers, your mileage will vary with car air purifiers depending on the particular device. So-called purifiers that include a single filter, or don’t conform to HEPA or HESA standards, are unlikely to do a satisfactory job. And in the same way, a car air filter that includes a HEPA filter but not a HESA filter may leave your car still smelling like smoke, or hamburger grease, or whatever, while it will still do a fine job of removing pollen, bacteria, and other impurities.

As an example, the Philips GoPure claims that its HESA technology is three times better than ionizers at removing tobacco smoke odors.

Choosing the Best Car Air Freshener, Filter, Purifier or Ionizer

The best way to get rid of bad smells in your car will depend on exactly what smells you’re dealing with, and exactly how bad the situation is, so there’s no one size fits all solution.

For instance, if someone smoked in your car and it smells a little bad, installing an ionizer or an air purifier with a HESA filter may do the trick. If the smell is stronger, or more baked-in, then you might have better luck absorbing some of it with charcoal, treating the carpet or upholstery with baking soda, or even using a commercial deodorizer before you try an ionizer or purifier.