So it's pretty common that people say that torches can do a single point of fire damage to swarms. However, my group can't seem to find any sources that confirm this.
Basically, it comes down to the idea that since a torch does 1d3 bludgeoning + 1 fire, swarms take 1 fire damage. But, "A swarm composed of Fine or Diminutive creatures is immune to all weapon damage." and "A swarm is immune to any spell or effect that targets a specific number of creatures…"
There's nothing that I can find that says the fire from a torch is an area of effect attack, which would be the key to actually damaging them. Weapons, as far as I know, attack a single target, so is a torch effective at all?