One of my friends has the Volcano vaporizer. He's only used it a few times, once with me, and he's actually selling it to me for about $50 cheaper than what they are on the market.

The first time he heats up a bowl, he heats it up at 5. Second time, 7. Third time, 9. He gets great use out of his bud this way. I would suggest doing it this way and see how things work out for you.

Also, you mention something about "bad chemicals" being released. If you're using a Volcano vaporizer, then the technology is designed to eliminate bad chemicals, odors, etc. Pretty much what you're getting is fresh oxygen mixed with fresh and pure THC for inhalation.