i thought Rule One was to NEVER hold fireworks in your hand while lighting them ...
[also, never throw live ammunition in a camp fire to see what happens, but that’s another story.]
I lived in Madison, Wisconsin, from the mid-70s to the mid-90s. Sometime in the 1980’s my wife and I went over to the country club and watched the fireworks display from the golf course. People would lay beach towels and blankets on the greens and lie back to look up at the fireworks, which detonated overhead and had an amazing effect in filling your field of view. The fireworks casing materials would float down on you as you were watching, but nothing dangerous. All of a sudden, the fireworks stop, and the radio synch-cast stops, and that’s it, show over. Sirens blare, and firetrucks race past as everyone heads home. The next day in the paper is the explanation that one of the fireworks company’s mortar tubes misfired, and an employee looked into the barrel to see what was wro... and, well, you get the rest. The fellow was decapitated. And he was an alleged professional.
Not only ammunition in the fire, but wet, porous rocks, too. They heat up, the steam expands, and the rock explodes. It was great fun when we were kids. Luckily nobody lost an eye.
Best I can do is never roast chestnuts in a microwave. I still find specks on the ceiling.