I've been burning a large stump lately, and fueling it with garbage firewood. I had a couple of dead alders fall last year and I processed them just for using on the stump. I'm out of wood to sacrifice to the stump now, so I loaded my pickup with free broken pallets from a business. All the stamps on the pallets indicate they were only heat treated and don't contain any chemicals. I don't know what was transported on these pallets or what kind of business gave them away. But roughly 1/3 of the wood smells like burning tires when it burns. I'll probably end up spending $20 to dispose of these free pallets at the dump.
Thats too bad... Maybe post a picture of the heat treat stamp. Someone maybe able to identify for you?
I was in the area where I got the pallets today and drove around back to see what they might do. The mystery of why the pallets smelled like burning tires is solved. What are the odds. Right after that I scored at a place that processes and packages vegetables. They had a few pallets plus a big bin of broken pallet pieces out for the taking.