A fire in your fireplace can be a soothing site. A fire in your chimney though? Not so much. Chimney fires can occur when your chimney is too dirty. When not properly cleaned, your chimney can become clogged over time, and this can lead to a chimney fire. What makes these fires especially dangerous is that they can sometimes burn slow and not be visible from the fireplace or the top of the chimney. Over time though, these fires can reach high temperatures and spread through the rest of your home.