The new study used a gas chromatograph mass spectrometer (GCMS) to examine the gas components of the vapor. .The analysis showed that the Volcano® vapor was remarkably clean, consisting 95% of THC with traces of cannabinol (CBN), another cannabinoid
Non-cannabinoids accounted for as much as 88% of the total gas content of the smoke
A quantitative analysis found that the Volcano® delivered 46% of the THC into vapor following three 45-second exposures of the sample to the heat. This compares favorably with the typical efficiency of marijuana cigarettes as observed in other studies, which depending on conditions can fall below 25% due to loss of THC in sidestream smoke. An important feature of the Volcano® is that it uses a balloon to capture the vapor, thereby avoiding leakage to the air. It is possible that higher THC efficiencies could have been reached with the Volcano® by stirring the sample around and exposing it to more heat.
Quotes from this study :: http://www.canorml.org/healthfacts/vaporizerstudy2.html