Sorry, for the interruption, but most smokers would like to check this out. I've posted this time and again.

The MAPS-NORML study provides new information on the efficiency of different devices in delivering THC from marijuana to the user.

The percentage of total THC delivered to the user is called the THC transfer rate. The unfiltered joint scored surprisingly well in smoking efficiency, coming in second place with a transfer rate close to 20%. The portable waterpipe did slightly better, and the bong slightly worse. The other devices did notably worse. The vaporizers and electric waterpipe did especially poorly, with transfer rates less than one-third that of the top three devices. Thus, heavy smokers could literally be blowing most of their stash away with bad pipes.