While retailers and developers turn to positive smells for advertising and marketing, the U.S. Department of Defense has realized the value of bad smells — really bad smells. Unlike pepper spray or tear gas, which irritate pain receptors and can cause serious damage, stink bombs just reek and make unruly crowds disperse in a flash.The idea of using smell as a weapon has been around for some time, however. The Office of Strategic Services for the French Resistance considered using a horrific garbagelike smell called “Who Me?” against German soldiers in World War II. The only problem? The sulfur that made the scent so pungent had a nasty habit of escaping on its own and lingering on everything it touched.
http://health.howstuffworks.com/smell4.htm