Fire is fun. Colored fire is even better. These additives are safe. They won't, in general, produce a smoke that is any better or worse for you than normal wood smoke. Depending on what you add, the ashes will have a different elemental composition from a normal wood fire, but if you're burning trash or printed material, you have a similar end result. In my opinion, this is suitable for a home fire or campfire, plus most chemicals are found around the house (even of non-chemists).
This mechanical weathering experiment teaches kids why and how rocks break down or erode. Take two pieces of clay, form them into balls, and wrap them in plastic wrap. Then, leave one out while placing the other in the freezer overnight. The next day, unwrap and compare them. You can repeat freezing the one piece of clay every night for several days to see how much more cracked and weathered it gets than the piece of clay that wasn’t frozen. It may even begin to crumble. This weathering also happens to rocks when they are subjected to extreme temperatures, and it’s one of the causes of erosion.
But the point is, I had not done any of these experiments with my daughter until we got this box. This has everything in one box, with all the equipment-- including a stand for the test tubes, which another review didn't have for some reason. (And get a little bag superabsorbent polymers, too. Those little buggers are fun but somehow end up everywhere). It's fun, it's easy, there are some experiments that require patience, which is really good for this age group. We are most of the way through the kit, doing maybe three experiments a week, and now I am shopping for more kits. Because even though I have the equipment, the books, and the education to diy the whole thing... the kit is easy, fun, and we actually DO it.