When I took CS gas training with the army we were warned that they will ignite wooden buildings. Some police may use this fact to intentionally use them to burn down buildings around suspects. 'Burn', the term used in the tape, may refer to CS or smoke canisters that would have the dual effect of smoking a person out or burning the building down if they don't come out. I may still have the military manual on them somewhere, if not it may be online.