MEDFORD, Ore. — Crater Lake Ford specialist Bill Newell recommends that motorists change their car air filters as soon as fire season ends.

"That way you know what you're breathing, and afterwards it's nice, clean air...not full of ash and pet dander and human hair, pet hair, that kind of stuff," says Newell.

A new air filter is pristine white. But after about 15,000 miles on the road or a relentless fire season—like this one is destined to be—it could appear a mottled black, clogged with unidentifiable matter. That's when it should probably be replaced.

"I opened it up so you can see the stuff that's in here," Newell says, holding the blackened air filter pulled from a Ford Fiesta. "Yeah, it's kind of gross...but you can see all the ash and hair from I-don't-know-what. And there's just a lot of stuff inside here. And the ash is so fine, you can see that it makes its way through the back side."

Newell says that a car driving frequently along dirt roads or in heavy smoke should have the air filter changed closer to every 7-10 thousand miles.

"It really helps people who have allergies, keeping that air filter clean makes it so that the inside air is nicer for them," Newell says.

For motorists that are unsure when or how to change their air filter, there are generally instructions to be found in the vehicle's owner's manual.