Recently a friend of mine and I smoked out of this vaporizer type bong. He is a chemist and explained that the weed gets "vaporized" so when you inhale its kind of like a THC "mist".
It was kind of wierd b/c you weren't inhaling a lot of smoke it was a very light mist. I caught a very nice long lasting buzz off of it.
Check this site out for more info (i just googled it for you)
http://shop.grasscity.com/cgi-bin/gr...ml?id=F5fIYjm3