The highest temps I would try for is 250F to do brisket and pulled pork. This will mainly be for cold smoking and sausages and hams though. Stuff like that.
This is the one I am looking to use.
I emailed their customer service to ask about if they are available untreated.
The CSR said that it is not dip or pressure treated.
She did say that there is some treatment used for delivery purposes.
I emailed back to see if I can find out what that would be.
I have looked all over ebay here and can't find sheds that are untreated.
I will update this post if the CSR emails me back with more information.