@aart, what is the reason for letting it age?
I'm going to have some oak trees taken down, and I will have a LOT of chips from this. It'll probably be in the next month, probably, so lots of green leaves in the pile.
Yes, mostly.......moisture and heat from initial decomposition can cause molds, already growing in normal and balanced populations on the bark of trees, to grow to toxic amounts.The moisture, especially from the leaves, can cause a specific sort of mold.
The main one is aspergillus.