Summary: South Metro Fire Rescue responded to a carbon monoxide (CO) alarm at Copper Mesa Elementary, located at 3501 Post in Parkway, Arapahoe County, Colorado. Engine 20 was dispatched to the scene. Upon arrival, crews made entry into the building and checked the boiler room. No sick parties were reported, and no hazardous readings or active alarms were found. The crew cleared the scene and returned to service.