On the B1900 (the USAir version if it matters) has air vents, but you can't turn them off! They're really huge, too, about two inches wide. It's on the wall in front of you.

When I board a plane, the first thing I do is close the air vents over my seat and all the other seats in my row (unless someone else is already there). Blowing around dirty air is not going to make it any cleaner, and blowing around hot air is not going to make it any cooler. The stream is too narrow to get the cooling feeling of a fan -- it's more like releasing a ballon in your face.

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"Yippie-kay-yay, Mr. Falcon!" -- John McClane, Die Hard II As Seen on TV