A smoke detector that Gwinnett County firefighters installed in a Loganville area home last summer helped save the lives of the couple that lived in the house as well as their dog this week, according to fire department officials. Capt. Tommy Rutledge said firefighters were called to the home on the 3400 block of Brushy Fork Road in Loganville at 2:30 a.m. Thursday on a call about a smell of smoke and a smoke alarm going off. The couple evacuated the home after calling 911. Crews found a fire in the exterior wall on the back of the two-story home and it was moving upward. Firefighters were able to stop the fire from spreading to the living spaces in the home. Investigators believe the fire started at an electrical outlet and have ruled it an accident. “There was extensive damage to the exterior wall and only residual smoke and water damage to the affected area inside the home,” Rutledge said.