Cut one large poster board in to four equal squares.

Use a permanent marker to write the location where you plan to put each of the four squares across the top of the square. For example, you may write "home" on one poster board and "bus garage" on another.

Punch a hole out of the top center of each of the poster boards, and string a piece of yarn through it. Leave enough room to make a loop to hang the poster board, then tie a knot.

Draw a medium-sized square in the middle of each of your poster board squares. They must be exactly the same size to make the experiment fair.

Cover the inside of that medium square with petroleum jelly.

Hang your poster boards up in the location that is written on them. Wait five to seven days, and then go pick them up.

Examine which places had the most air pollution by using a magnifying glass to count all of the particles that collected on the petroleum jelly squares.