DIY air purifier: breathe easier!

My family has a lot of environmental allergies, so we like to keep several air purifiers going at all times.  We also currently leave near a construction site, so there is a lot of dust in the air!  The air purifiers you buy at the store are expensive and so are the filters you have to buy on a regular basis in order to keep them functionimg.  Here is a simple way to make your own air purifier, using furnace filters, which you can get for less than $10 at your local hardware store.

    

MATERIALS:
-a box fan
-furnace filter that is the same size as your box fan.  Mine are 20 x 20, but the size is really up to you.   Also, I like to buy the filters that catch dust and pollen.  Just read the label to fnd out what types of particles the filter can remove.
-heavy duty tape.  (Duct tape, pacing tape, etc)

DIRECTIONS:
-measure your fan to make sure the furnace filter will cover the surface
-use the tape to affix the furnace filter to the box fan.  I recommend that you use the tape sparingly so that it is easier to remove and change the furnace filter later on.
-plug it in and enjoy your clean air!
-remember to change the filter when it starts to look dirty.