At ~1:47 AM, Westmorland 911 dispatched Station 20 (Murrysville VFC) for a Residential Carbon Monoxide Alarm at a home on Millstream Court. Station 20 responded with Engine 20 (2 firefighters including Lieutenant 20). Murrysville Police and Murrysville Medic One were already on scene when Engine 20 arrived, and the home owner had self-evacuated the structure. Engine 20"s crew searched the home's interior both visually and with Four-Gas Meters, but found no evidence of carbon monoxide. The firefighters reset the detectors and no additional alarms were sounded. Lieutenant 20 returned Engine 20 to service for return to station.