There is no way a home or automobile heating track can even carry enough heat to ignite a shell unless it was litterally on fire, and if your worried about a shell being dangerous in such a fire, well it wouldn't. The plastic will melt long before the primer ignites, when it does eventually go off it'll be little more than a loud pop from burning wood.
Throwing .22 shells in the fire is pretty close to tossing a pine bough on a fire. If I was standing near a fire that some #### dropped a targed load in I'd do nothing more than turn my back until it went off, while I'll run like hell it a can of beans is thrown in.
So don't even think about it, unless like me a can't waste a single shell. I'm sure I've ruined my .22 barrel by picking who knows how many shells off the ground and shooting them.