One form of fireworks, firecrackers, can frighten unintelligent animals.
Raw this is clear, but [b]Should[/] this work on vermin and perhaps even swarms, too? we've had several cases, where we tried to use firecrackers in one of our games and, curiously, in most of those cases the target(s) were really vermin not animals.
So, would you let it affect it a vermin?
How about swarms of animals or swarrms of vermin?
I was going to bring up rats, but looked it up and was happy to see they are more correctly categorized as animals.
I don't know the various kinds of vermin off-hand, but I'd say it would depend (GM's discretion). Things like insects should be scared off by loud noises, they don't really have the mental faculties for that kind of response (usually).
Light scares cockroaches.
Seismic vibrations that mimic a stomping foot will scare most bugs.
You can chase a spider into a box and throw it out the window, no harm to the spider, but a swarm is probably bolder. A swarm of spiders you cannot scare with a broom.