What type of wood chips for a run?

[Raubkatze]

I got the "plain" no color added, no chemicals added to make it last longer mulch from Menards. It was $2 a bag. It's been in my run for about a month and so far so good. My run has a roof on it so it doesn't get exposed to rain except along thr edges. I "turn" it just about daily because the girls love to dig holes in it and I have yard cloth down as my base (there was an invasive vine in the spot we picked for the coop, didnt want it coming back after we pulled it out) that I dont want them getting to. I just scrape it back from the edges to fill in the spots they have dug up. I'd say mine is about 4 inches at the middle, tampering out towards the edges. So far I haven't noticed any smell. I imagine the poop will break down naturally within it because it's getting turned over by me and the chickens regularly. At least that's my hope.

 

[Folly's place]

The only possible issue with tree trimmer chips would be high amounts of black walnut chips (easy to see because of their dark color) which are toxic for some animals to eat or bed in.
Mary