Hou do you measure a fart's smell?
When someone farts, people go away from him/her. Measure the distance how far people went. that's an easy way to measure. :)
Look up, "Off the Pill: Farts" by Nigahiga. It doesn't measure smell but it identifies the types of farts. I can't believe I just typed that.
1-10..... Haha(x I guess from loud to silent killer .
You fart, and then have your friend fart. Smell both, and compare whose is better :)
By how many people flee from the room!