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Ria Misra, an editor at Wirecutter, has traveled on her own throughout three continents. Air Filter Company
Any cabin air filter can pull out at least some pollutants from the air inside your car. But the gold standard is a HEPA (high-efficiency particulate air) filter, which is so effective that it can capture the vast majority of allergens, dust, mold spores, and even viruses that are circulating in the air.
That kind of higher-level filtration can benefit you at any time (especially if you have seasonal allergies or routinely drive in an area with poor air quality), but it becomes particularly useful during a wildfire. Unfortunately, many cars—especially those that are a few years old, like mine—don’t have the most effective filter.
But switching over to a stronger, HEPA filter—the same kind that many at-home air purifiers use to clear the smoke, dust, and particulates present in the air during a wildfire—is effective and inexpensive, and it takes only a few minutes.
I was able to make the switch in under 15 minutes, without a single tool. Here’s how you can, too.
When I swapped my car’s cabin air filter, the Los Angeles area was already on fire, the air clogged with smoke, ash, and a throat-puckering, eye-burning mixture of gases while about 40,000 acres burned.
A few nights after the fires began, the evacuation orders crept close enough to the borders of my neighborhood that it seemed wise to get my car gassed up and packed with the essentials before the long night ahead.
I’ve had enough proximity to wildfires that the smell of stale smoke permeating the air has become a familiar feature when one is nearby. But whatever was in the air on this night felt different, a gritty cocktail of black-and-white particulates that gusted around me as I moved between my car and home, the smell more like tar than smoke.
I ended up not needing to evacuate that night. But when I awoke the next morning already coughing and with my throat thick and swollen, the thing that I’d neglected in all my hurried nighttime preparations—an N95 mask to cover my nose and mouth—became clear.
I wanted another layer of protection, one that wasn’t as easy to leave behind as my home air purifier or my forgotten respirator mask. Over the next few days, I began looking into how to upgrade my car’s air filtration.
One of the first people I consulted was Wirecutter’s resident expert on air quality and filtration, senior staff writer Tim Heffernan. Tim has reported on and tested all kinds of air-filtration systems, from air purifiers to respirator masks.
“HEPA filters are exceptionally effective at capturing the incredibly fine particles in wildfire smoke—it’s one reason I use smoke to test air purifiers,” Tim said.
Different car manufacturers have different recommendations about how often to swap out your cabin filter (the recommendation for my Subaru is 15,000 miles). But if your car’s filter has been unusually taxed by extreme conditions, such as a wildfire, it might need more frequent replacement—especially if it has become visibly clogged (more on that in a second).
Considering how simple and cheap it is to do yourself, you can replace your cabin filter as often as you need to—whether you’re simply preparing for a coming wildfire season or, as I was, already right next to one.
The trickiest part of swapping your car’s cabin air filter to a HEPA filter is determining which size filter will fit into your car’s air system. To find out, you can search for cabin-filter sizes in your car’s owner manual or look it up online by either the VIN (vehicle identification number) or your car’s year, make, and model. You can use any HEPA filter (it will be labeled as such) that you know fits your in car. But the Bosch HEPA cabin filter that I used has an online tool to confirm that you’re getting the proper size.
From there, exactly how to change out your air filter varies by car, though in most cases the process will be simple. In my 2021 Subaru Outback, the filter was located behind the glove box. This is true for many cars, but not all. If you’re not sure, check your car’s manual to find its specific location and how to access it; the spot could be elsewhere along the dash.
If your air filter is located behind the glove box, as mine was, you need to remove the glove box. This task is relatively easy. On my car, I simply cleared my glove box, detached the latch locking it in place, and popped it from its hinges.
With my glove box removed, I could see a cartridge exposed on the wall of the car. Inside—covered in layers of dust and ash that had blown in from the air outside—was my car’s congested, struggling cabin filter. (I recommend wearing a mask and latex gloves for this part, especially if your car has already been through a wildfire.)
I’m not a mechanic, not even an amateur one, but the process of switching the filters was simple. It reminded me of nothing so much as swapping two videotapes in a VCR.
After latching the glove compartment back on its hinges, I flipped on the air conditioner. It kicked on right away, just as strong and evenly flowing as before. (Some online car forums report that HEPA filters can reduce airflow, but I have not noticed any difference.)
In under 15 minutes, without a single tool, I had added a layer of HEPA filtration inside my car.
It’s difficult to anticipate exactly what I’ll need to do to be ready for the next wildfire. I know that next time there will be more things I forget, more things I won’t yet know to do until the problems are already at my doorstep.
But having this small thing done—and knowing that I can do it again, whenever and as often as I need to—makes me feel just a little better prepared for when the next wildfire season comes. And, in the meantime, knowing that my car is better guarded against dust, allergens, and other particulates makes me breathe a little easier, too.
This article was edited by Katie Okamoto and Megan Beauchamp.
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Ria Misra is the editor at Wirecutter for travel and the outdoors. Previously, she was an editor for Gizmodo and io9 and hosted a music podcast for American Public Media. You can also catch her byline on PBS, NPR, the BBC, Wired, NewsHour, Smithsonian, and more.
Air Compressor Filter Wirecutter is the product recommendation service from The New York Times. Our journalists combine independent research with (occasionally) over-the-top testing so you can make quick and confident buying decisions. Whether it’s finding great products or discovering helpful advice, we’ll help you get it right (the first time).