Here's a quote:
"Few vaporizer studies/reviews have really addressed the quality of the vapor extracted and delivered. Most studies/reviews have tended to focus on the mode of usage of the vaporizers and not the quality of the vapor extracted and delivered. When one considers that there are at least 60 pharmacologically-active compounds in cannabis and that the aromatic terpenoids begin to vaporize at 126 °C, but the more bio-active
cannabidiol (CBD),
Cannabinol (CBN), and
delta-9-tetrahydrocannabinol (THC) do not vaporize until near their respective
flash points: CBD 206.3 °C
[6], CBN 212.7 °C
[7], THC 149.3 °C
[8] then it becomes apparent that the only way to get a full spectrum vapor inhalation is to extract and deliver rapidly from a small sample at a time. Because most commercial vaporizers are slow in extraction and delivery, the vapor inhaled is first aromatic, but only minimally active; and then as the apparent temperature rises, the vapor becomes increasingly bio-active, but minimally aromatic as most of the aromatics already released."
...from this article:
Vaporizer - Wikipedia, the free encyclopedia
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Marijuana, in its natural form, is one of the safest therapeutically active substances known to man.
By any measure of rational analysis marijuana can be safely used within a supervised routine of medical care.
FRANCIS L. YOUNG, DEA Administrative Law Judge