Dry herb vaping has been around since the late 1990's. The dry herb vapes from then and even into the millennium weren't easily portable devices. The best dry herb vaporizers were large tabletop devices that required being plugged into a wall socket. However, with the popularity of pen-style vaporizers growing over the past few years, dry herb vape technology has improved drastically.
Vaping herbs is much different than vaping e-liquid. Because of this, there are 3 things that dry herb vapers should avoid: vapes that cannot regulate temperature, using completely dried out herbs, and combustion.
First and foremost, dry herb vapes need to be able to regulate the temperature. This is very important when vaping certain herbs due to the fact that different chemicals in them have different vape points. Just about any herb anyone would want to put in their device has detailed information about what's extracted at certain temperatures. If the active ingredients in the herbs don't get vaporized, what's the point? Being able to regulate temperature is crucial to ensuring that you can actually vaporize what you're trying to vaporize.
Next, it's very important to make sure the herb has some moisture in it. Fresh herbs are good for vaping for that reason. Having moisture in the herb allows for more vapor production, as generally vape points are above boiling but below the point of combustion. Therefore, if there's moisture in the herbs, there will be more voluminous vapor production. This isn't to say that your herbs should be wet, or even feel moist, but they should not be bone dry, or at the point where it will crumble into a dust or powder. Even cured herbs can still have moisture in them.
Finally, combustion isn't vaping. Using a dry herb vape to actually burn or char herbs is no different from simply smoking. This is another reason why temperature regulation's important. Vaping's cleaner than smoking, so why use a vaporizer to burn herbs? Additionally, when herbs combust, they leave burnt carbon and residues that make the vape chamber dirty, which can even destroy these devices.
Herbal vaping has come a long way since the 1990's and is now enjoying a revival of sorts like never before.