Winter's stale indoor air can finally be banished simply by opening a window in warm spring weather. But if you don't clean your window screens, that fresh breeze could blow accumulated dust and debris into the house. Remove the screens and stand them in the tub on top of a towel. Wet them down with warm water and then spray them with a degreaser. Then gently scrub away any grime and dirt, and rinse them. Tap them to remove excess water and let them air dry before replacing them.