At ~ 12:45 PM, Westmoreland 911 dispatched Station 20 (Murrysville VFC) for a Carbon Monoxide Alarm at a home on Forest Ridge Court. Station 20 responded with Engine 20 (4 firefighters) and Squad 20 (2 firefighters including Lieutenant 20). Engine 20 and Squad 20 arrived at the scene, Lieutenant 20 established command, and found the occupant of the home was out of the structure. Engine 20 firefighters entered the home using Self-Contained Breathing Apparatus (SCBA) and surveyed the home using 4-Gas Meters. No Carbon Monoxide was detected, and it was determined that a faulty detector had tripped the alarm system. The home owner was advised to replace the defective detector, and Command 20 returned all Station 20 units to service and station.