At ~ 5:31 AM, Westmoreland 911 dispatched Station 20 (Murrysville VFC) for an Automatic Fire Alarm (AFA) at the former Weyerhauser Lumber Warehouse on William Penn Highway. Station 20 responded with Truck 20 (3 firefighters), with Chief 20 and Lieutenant 20 going directly to the scene. Westmoreland 911 also dispatched the following stations to support Station 20: Station 22 (Export VFC), Station 610 (Murrysville Medic One), Station 64 (White Valley VFC), Station 78 (Sardis VFC), Station 236 (Holiday Park VFC), and the Murrysville Police. Murrysville Car 229 was first on scene with nothing evident. Truck 20, Engine 22-1, Support 610, and Medic 611 arrived on scene and began investigating the source of the alarm. Lieutenant 20 established initial command, and all units not on scene were cancelled by Command 20. The Fire/EMS/Police units gained access to the property, with the crews of Truck 20 and Engine 22-1 entering the warehouse, and after a search of the structure found that a smoke detector in the office area had falsely activated the AFA System. The Property Key Holder arrived on scene, and the AFA System was reset. Command 20 returned all on-scene Fire/EMS/Police units to service and station.