Here's a simple solution we use some times. You will need:
A toilet paper or paper towel tube (the cardboard tube inside)
2 Rubber bands
2 Paper towels
1 - 3 Dryer Sheets
Ground Incense, potpourri, anything that smells good (optional)
1) Cover one end of the tube with one of the paper towels.
2) Secure it with a rubber band.
3) Fill the tube with the Dryer Sheet(s) and add the optional stuff.
4) Use the other paper towel and rubber band on the other end of the tube.
Now, when you need to freshen the air, blow through the tube!
Remember, never try to suck air in using the tube, also keep it out of reach of children who might get hurt with this.