At 10:14 AM, Westmorland 911 dispatched Station 20 for a report of a Residential Carbon Monoxide (CO) Alarm activation at a home on Lyons Chase Circle. Station 20 responded with Engine 20 (5 firefighters including Lieutenant 20 and Sergeant 20), with 3 firefighters manning Station 20. Upon arrival at the scene, Engine 20's crew metered the home's interior with Four-Gas Detectors, and inspected the activated CO Alarm. No CO was found in the home, and the CO Alarm was found to be defective. The firefighters advised the homeowner to replace the defective alarm. Lieutenant 20 released Engine 20 for return to station.