At ~ 1:09 AM, Westmoreland 911 dispatched Station 20 (Murrysville VFC) to assist Station 64 (White Valley VFC) for an Automatic Fire Alarm (AFA) at Brookdale-Murrysville on Old William Penn Highway. Station 20 responded with Truck 20 (3 firefighters), with Assistant Chief 20 going directly to the scene, and 1 firefighter manning the station. Assistant Chief 20 was first on scene, observed no smoke or fire coming from the structure, and directed the positioning of Engine 64 and Truck 20. Captain 64 established the scene command, and upon investigation found that an air compressor which is part of the facility sprinkler system had malfunctioned, and set off the AFA System. The facility staff placed the AFA System into a safe mode, and requested that the sprinkler system service company to the facility, and effect repairs on the air compressor Command 64 returned Truck 20 and Engine 64 to service and station.