As Halloween approaches, you might notice a few spooky things happening around your house, but not all eerie occurrences are due to ghouls and ghosts. Sometimes, the culprit is much more mundane—and scarier in its own way—a problematic furnace. When your furnace starts acting up, it’s crucial to recognize the signs before things go from creepy to costly. Here are five spooky signs your furnace may be in trouble and in need of attention.