I'm gonna agree with Kevin here. Treated wood has been stained by the treatment. It's usually a compound of copper.
Crash, back me up on this. Most of the wood available in Hawaii is treated stuff. In fact, Hawaii has stronger treatment.
But, if the color looks OK, and there isn't little dimples on the wood (they gotta get the stuff in there, somehow) use it.
But, serious wood, anything that would end up in furniture, should be OK. If you live where Crash does, construction lumber would be questionable, until you look. (But, who is using construction lumber to smoke with? Unless you're building with serious oak.)
steve