Swapped out my cabin air filter yesterday with a charcoal activated one. Was catching a whiff of something old when I fire up the AC...did some research on filters and they suggest replacing it every year...huh..didn't know that. They said your cabin air can be 6 times more hazardous than the outside air if the filter is old. Simple swap and good price for better air. Suppose to filter smoke which has been horrible in MT. this year. My eyes burn after awhile from the smoke so I hope these help. Drove to Spokane and back which is around 750 miles roundtrip. My eyes were burning bad when I got home. Sometime visibility was less than 1/2 mile from the smoke. Nasty smoke this year from the fires ....native Montanan and this is the worst I've seen in my 65 years. What global warming ......