Shortly after 11:00pm Friday evening, Station 39, Ladder 53, and 55 Ambulance received the dispatch for a chimney fire in the Newlin Twp section of our district. Before any units made the response the assignment was upgraded to a chimney fire with possible extension into the walls, which brought additional units from Stations 36 and 37. Chief 39 arrived to report smoke showing and fire extension into the walls. The crews arrived to ladder the dwelling and send personnel to the roof to cut a ventilation hole and expose the area. The interior crews worked to remove wall board and other building materials around the fireplace while checking for extension. Crews exposed the area and extinguished the fire that had extended from the firebox into the dwelling. The homeowner advised they were sleeping and were awakened by their smoke alarm activating, finding the home filled with smoke and called 911. We cannot stress enough the importance of working smoke and or carbon monoxide detectors as if the residents were not alerted by the smoke detector this incident could have been much worse. Smoke detectors are a very important part of early fire detection and could be a life saver as well as saving property.