Do Car Air Purifiers or Ionizers Really Work?

Car air purifiers, ionizers, and ozone generators

Most people never even think about the quality of the air inside their cars, but it is a subject that bears some attention. On average, we spend about 5.5 percent of our time in our cars, according to one study on the air quality inside vehicle cabins, which is a significant amount of time to seal yourself in with some pretty bad air.

Dealing With Bad Air In Cars: The Problem With Car Air Purifiers

Car air purifiers do exist, and some of them actually work. The problem is that car air purifiers typically don't work in the same way, or as well, as the air purifiers you probably use at home or work. If you're expecting similar results, you'll probably end up disappointed.

This is why it's important to temper your expectations any time you’re dealing with car air fresheners, purifiers, ionizers, and similar gadgets. Most of these devices are actually ionizers, which work via a completely different mechanism than the (high-efficiency particulate air) HEPA filters that are so common in home and office environments.

The fact is that ionzers don’t actually filter particulates out of the air, and even big, expensive units that are designed for home use have drawn the ire of consumer advocacy groups. They do work, in that they do what they are designed to do, but that may or may not line up with your expectations for an air purifier.

Other types of car air purifiers work by generating ozone, which is a whole different can of worms. These devices can certainly knock out some powerfully baked-in smells, but they're typically better left to professionals.

The Quality of the Air Inside Your Car

When most people think about air pollution, they think about smog, pollen, and other outdoor air quality problems. The next thing that typically comes to mind is indoor air quality, which usually becomes a bigger problem during especially hot or cold weather, when dust and other allergens are allowed to collect inside homes and businesses that are sealed up against the elements.

The fact is that indoor air pollution is also a problem inside cars, so the idea of car air purifiers actually has a lot of merit. All of the same pollutants and allergens you find outside are present inside your car as well, in addition to chemicals and particulates that come from the car itself.

For instance, an analysis performed by the National Institute of Health found that particulate matter from brakes, and aromatic hydrocarbons that come from various interior components, can cause health problems. One solution is to simply roll down a window, but that just allows all of the pollution from outside the car to get inside.

Another air quality issue that a lot of people have to deal with involves lingering odors from tobacco and other sources. Purifiers and ionizers usually won't help with this type of problem, but you may have luck with adsorbents or ozone generators.

Types of Car Air Filters, Purifiers and Ionizers

There are a few different types of air filters and purifiers that you can get for a car, including:

  • Engine air filters - These filter the air that goes into your engine for the purposes of combustion. They don't have anything to do with the air quality inside your passenger compartment.
  • Cabin air filters - These filter the air that comes into your car when you have the heating, ventilation and air conditioning (HVAC) system set to draw in fresh air. They may also filter air that is recirculated.
  • Air ionizers - These are electronic devices that are typically plugged into the cigarette lighter socket. They operate on the principle of ionizing pollutants and causing them to stick to surfaces where you won't be able to inhale them.
  • Ozone generators - These devices actually generate ozone, which can effectively destroy the molecular structure of pollutants and bad aromas.

Each of these filters uses a specific method to perform a different function.

Air Filters in Cars

Engine air filters use a filtration media that is typically paper or cloth based to trap particles and debris and prevent them from entering your engine’s intake system. Unlike cabin air filters, engine air filters have absolutely nothing to do with the air inside the passenger compartment of your car.

Cabin air filters are an important part of maintaining an allergen and odor-free passenger compartment. Whereas older vehicles simply drew in fresh air through unobstructed exterior vents, newer vehicles use cabin air filters to trap particles and debris. There are two kinds of cabin air filters that may help reduce the allergens and odors in your car:

  • HEPA cabin air filters - These filters use a very fine mesh that's capable of trapping large particles, like pet dander, and extremely small particles, like those found in tobacco smoke.
  • Cabin air filters with activated carbon-impregnated filtration media - Filters with activated carbon are especially good at eliminating odors.

In most vehicles, the cabin air filter is still in play even when you set the HVAC controls to recirculate. This setting prevents new air from entering the vehicle and simply recirculates air that's already in the cabin, so it can effectively prevent the introduction of new pollutants while filtering out existing pollutants.

Cabin air filters work better than ionizers, but you need to replace them regularly.
Mihajlo Maricic / EyeEm

Some vehicles, especially older vehicles, don't have cabin air filters. And some older vehicles that do have cabin air filters have them placed in a location where they are unable to filter air as it recirculates inside the cabin.

If your vehicle has a cabin air filter, and it is capable of filtering recirculated air, regularly installing a fresh HEPA or carbon-impregnated filter is the best way to improve the air quality inside your car.

Do Car Ionizers Work?

Air ionizers that are designed for automotive use are typically compact units that you can plug directly into your cigarette lighter socket. Instead of filtering the air, these devices emit ions, which are essentially just molecules that have a positive or negative charge instead of the normal neutral charge.

The basic idea behind a car air ionizer is that ionized particles of various allergens and odorous materials will either stick to surfaces or each other, at which point they won’t be floating in the air anymore.

Although a good air ionizer should do what it is designed to, it won’t actually filter anything, and you may find yourself dealing with a dark coat of dust, pollen, and whatever else clinging to every surface inside your vehicle.

The other issue to look out for is that a lot of the small, weak ionizers that plug into a cigarette lighter are too anemic to even accomplish that much.

Do Ozone Generators Work for Smelly Cars?

Like ionizers, ozone generators don’t actually filter the air. They generate ozone, which interacts with various odor-causing chemical substances, often rendering them odorless. For some sources of bad car smells, this works quite well.

Large ozone generators, which you can sometimes find at dealerships and independent repair shops, are often capable of generating tremendous amounts of ozone and removing a lot of built-up odors.

Of course, there are a number of health risks associated with prolonged exposure to ozone, so it probably isn’t a great idea to drive around with an ozone generator constantly running inside your car’s passenger compartment.

Car Air Freshener and Purifier Limitations

Since every type of car air freshener and purifier comes with such steep limitations, the best way to deal with car odors is to avoid creating them in the first place. If it’s too late for that, then it may be worth it to check into whether any of the dealers or independent shops in your air can perform (or even recommends) an ozone treatment. Substances like activated carbon, baking soda, and pumice stones can also soak up some bad odors.

Car air fresheners, like the iconic ‘little green trees’ can also help with odors, although they only mask things like smoke and food smells instead of actually removing them, so your mileage may vary.

If you’re mainly concerned about allergens, then a good HEPA cabin air filter, or any cabin air filter with a sufficiently constrictive filtration media, is your best bet.

Although cabin air filters can’t do anything about the air that’s already in your car, they will prevent new allergens from entering. And since your passenger compartment isn’t a sealed environment, the introduction of allergen-free air will eventually displace most or all of the allergen-laden air.

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