Will an interior air-filtration system help my allergies?

Dear Car Talk

Dear Car Talk | Dec 01, 2001

Dear Tom and Ray:

Do car interior-air-filtration systems actually succeed at cleaning interior air? I've been searching all over the Web for credible info on this, but I can't zero in on any. Clearly, I'm desperate at this point. I have a 1987 Honda Accord LXI with 320,000 miles on it. It's in great shape and is a lot of fun to drive. I don't really want to give it up, but I am having problems with allergies. If interior-air-filtration systems work, I might actually break down and get a new car. Thanks. -- Eric

RAY: Some do work, Eric. It depends on the car. And it's not easy information to get.

TOM: The key is knowing what you're allergic to and the size of its particles. For instance, I'm allergic to my brother. And even a heap like yours has a filter that will keep him out. It's called "door locks."

RAY: Actually, we did some research. We called a couple of allergists, and for 150 bucks an hour, they told us that the most problematic particles for people who suffer from allergies are around 5 microns in size. Some are bigger. Ragweed, for instance, is about 17 microns.

TOM: For those without a scientific background, a micron is "very, very, very small." The current Honda Accord's filtration system will only stop stuff bigger than 8 microns. So that might not help you if you're allergic to 5-micron particles.

RAY: On the other hand, the Ford Focus' system gets stuff bigger than 3 microns. So that probably would do the trick.

TOM: But what if you're allergic to something like dust-mite debris, which can be as small as 0.5 micron in size? Then the Focus is out, and you have to either launch yourself into space or save up for a 2002 Saab 9-5. Saab says its filters can catch some particles as small as 0.25 microns.

RAY: So start by calling your allergist and getting as much information as you can. Then when you narrow down the list of cars that interest you, your best bet is probably to call the company's toll-free customer-service number. This is not something that dealers typically keep on the tips of their tongues. And besides, they might tell you anything to get you to buy their car.

TOM: And before anybody writes to ask, anthrax is about 1 micron in size, and viruses, like small pox, are a fraction of a micron. So living in your car for the next 40 years is not a practical solution to bioterrorism.

RAY: But it could ease the housing crunch!

Get the Car Talk Newsletter