Organic, fibrous, carbon based material can be classified as "wood," for the purpose of this discussion. "Wood" is composed of moisture, leaves and stem (and in some cases bark, trunk and root). Keep in mind that combustion does NOT mean burn.. combustion means creating noxious gasses, such as CO and CO2, through a chemical reaction. These noxious gasses do not naturally occur in the plant, are not intended by nature, and generally are harmful to the body. The Herbalizer will never exceed the threshold of combustion - 451 F - so you get all of the good stuff with none of the bad stuff, guaranteed.
This write-up explaining the Phases of Combustion is the best I've seen on combustion (go to section WHY AND HOW WOOD BURNS). Herbalizer testing leads to the same conclusions as are drawn in that write-up.
Using the temperature stability of the Herbalizer, I've run the fan for 6 minutes with a setpoint just above the threshold of combustion at 460 F (production units are limited to 445 F) across "wood" and then evaluated the ABV under a microscope. With its true temperature stability and long duration, the moisture is completely extracted, and combustion occurs. With postmortem visual inspection at 30x magnification, I consistently find carbon as indicated by blackened remnants - (black) carbon is the visual combustion indicator.
The reason that you can vape above 451 F and not get combustion is due to the moisture content that must first be evaporated - but once that moisture is gone on even the smallest area it will immediately combust (your senses won't notice at first, but your liver will). In practical application, above 451 F some parts will dry quicker than others and once dry they instantly enter phase I combustion, and mix with the vapor. At first it will be 99% vapor and 1% combustion gasses and you won't be able to tell, and then it will be 80% vapor and 20% other, and the 50%/50% and you will start to notice, and eventually all the moisture will be gone and there will be just combustion gasses. At 451 F it is incredibly subtle - but I can assure you that once the moisture is evaporated the "wood" begins to combust.
The bottom line is that you can enjoy really dense, milky vapor above 451 F - sure, even up to 600 F - for an incredibly short period of time. And you probably won't notice that you are combusting.. but that doesn't mean you aren't harming your body. If you want to prove it to yourself, inspect your ABV with a $10 30x handheld microscope - if you see black, turn the temperature back.