bling the stand, punch a small hole in the bottom of the can. Then nail the can to the pole.

   From one end of the cardboard, cut out a disk about 5 inches in diameter, and spread a thick coating of petroleum jelly all over the white surface. Lay the disk on the bottom of the coffee can (jelly side up, of course). Now you can start the test by placing the stand out in an open area as far above the ground as possible. Put a few rocks on the base of the stand to
keep it from being blown over. In a couple of weeks or so, you’ll be able to tell how clean or dirty the air is around you.