OK, I cheated -- voted for "other," but the ECO button and the RECIRC default are parts of it. Actually, I find the entire climate control system kind of dumb: much of the time the AUTO setting works out well, but if you happen to want fresh air and only fresh air, good luck. The typical sequence is:

1) press the fan button once, twice, maybe more.....
2) turn the temperature control to the lowest setting. Oh wait, not that low, you just turned off ECO mode!
3) turn the temperature control back up one notch
4) press the ECO button
5) oops, you just opened the fuel door. Stop the car, close the fuel door, restart the car, and then press the ECO button. (OK, this one doesn't happen often, but you get the idea)
6) oh wait, it's in RECIRC mode (for no reason known to mere humans). Press the RECIRC button for fresh air.
7) oops, the AC light is lit and the AC is going full blast. Hmmm, you didn't have it on AUTO. Too bad, the TCH thinks it knows best. Press the button to turn off the AC.

At this point, assuming that you have not crashed into the car in front of you while fiddling with the climate controls, you have plain old fresh air coming through the vents. It was a struggle, but you have prevailed against all odds......

Bill