From a camping trip too many years ago...

A group of us were camping, each night we'd drive somewhere else and everyone rotated duties...one night, the campfire wood collector was amazingly quick returning with the load of wood for the night. The other 11 of us were too busy setting up tents etc. trying to beat the imminent rainstorm. We all ended up rain soaked and ate cold dinner in our tents.

In the near darkness, we all failed to notice that he had brought back pieces of creosote coated railroad ties that had been discarded when an old railway was dismantled somewhere in the local area. At some point, the wood collector went back out after the rain stopped and lit a fire which stayed lit (barely) the rest of the night. Next morning, we all woke up with amazingly bad headaches from the fumes that resulted. At least we all woke up. Had we been in a less breezy area it could have been different.

Here are a few other things that you don't want to burn or cook over:
Brazilian Pepper trees, also known as Florida Holly.
Austrailian Pine trees.
Melalluca trees.
Poisen Oak, Ivy or Sumac.
Any tree or vegetation with white sap.
Building materials, i.e. plywood, tar paper, shingles, painted wood and the like.
There are many others.

Regards,
Comanche7