You snatch up the barrel, rip off the lid and in a childish fit of annoyance, hurl it at the creature.
It yelps and dives away, some liquid clinging to the lid as it crashes down where the poltergeist stood.
"So apparrently they can, huh?"
You muse and set the barrel down.
Taking out a match, you experimentally hold a little flame to the liquid, watching in amazement as a sparke forms, then the barrel smokes.
The smoke that rises is cloear and seethrew, not effecting your lungs at all but giving some serious outrage to old Mister P over there, who begins writhing in agony.
The smoke eats at his physical form, slowly taring it away until he disappears with a pop.

right, time to sort out old werewolf to the west then