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April 7, 2020, 11:00 a.m. EDT

How does a HEPA filter work in your car?

What do they really do? Are they effective against coronavirus?

By Andrew Ganz

iStock/Getty Images
A high-quality air filter is a basic maintenance item that should be changed regularly.

A HEPA filter is an effective way of significantly reducing airborne particles from entering a car, though it’s not a 100% safeguard against coronavirus.

Most new cars have cabin air filters that should be changed periodically, just like a forced-air HVAC system in a house. However, these filters are largely for keeping pollen and dust out of the car. HEPA (high-efficiency particulate air) filters do a better job of capturing even smaller particles than standard off-the-shelf units, like those probably installed in your car when it was new.

Theoretically, HEPA filters can capture particles as small as those that carry coronavirus, though quality varies by manufacturer, and the risk of airborne molecules entering your car while driving is low from the start. Coronavirus is airborne, but transmission requires the kind of proximity that doctors and the Centers for Disease Control and Prevention have largely ruled out when it comes to driving a car alone.

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Instead, the effectiveness of a HEPA filter boils down to tightknit, maze-like fibers that force tiny particles to bounce around and eventually become trapped instead of passing through the filter. Dirty air goes in, clean air goes out — that’s the idea.

What cabin air filters aren’t designed to do is filter air that’s already in a car. If your passenger is infected with coronavirus , a HEPA filter is too little, too late.

With that said, a high-quality air filter is a basic maintenance item that should be changed out at the car manufacturer’s recommended intervals. Drivers who spend time in dusty or high-pollution environments should consider changing air filters more often, and these consumers would benefit most from a HEPA filter.

Notably, an engine air filter is not the same thing as a cabin air filter, though both should be changed with regularity. An engine air filter does what its name implies: It traps dust, leaves and other airborne items that may be harmful to what’s underhood. Not all cars have cabin air filters, though most built within the past five years are fitted with them.

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Some newer cars are equipped with in-car ionizers, and devices that plug into cigarette-lighter-style power outlets can be easily acquired online. Kia and Hyundai (OTC:HYMTF)   brand their system as Clean Air, for instance, and the intent is to make polluting particles stick to surfaces rather than float around in the air. Ionizers do nothing to counteract the risk of airborne molecules that carry viruses, though again, they can help make the air inside your car cleaner. This is especially beneficial in a polluted city, or for drivers more sensitive to seasonal allergies.

This story originally ran on Autotrader.com.

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