At ~1:49 AM, Westmorland 911 dispatched Station 20 (Murrysville VFC) for a Carbon Monoxide Alarm Activation at a home on Cherry Lane. Station 20 responded with Engine 20 (2 firefighters), with Lieutenant 20 going directly to the scene. Westmorland 911 also dispatched Station 610 (Murrysville Medic One) and Station 64 (White Valley VFD) to assist Station 20. Lieutenant 20 was first on scene, establish command, and ensured the occupants of the home had evacuated the structure. Upon arrival Engine 20's crew entered the structure, conducted a primary search of the home using four-gas meters, while the crews of Rescue 64 and Ambulance 611 remained on standby outside of the structure. The search found no concentration of carbon monoxide within the home, and that the activated carbon monoxide detector was defective. Lieutenant 20 recommended that the homeowner replace the defective detector. Lieutenant 20 released all responding units for return to service.