Work Performed: * Responded to client’s concern regarding carbon monoxide detector beeping and flashing on the furnace after recent heat exchanger replacement. * Turned on my carbon monoxide detector to test for CO in the room. * Conducted a thorough inspection of the furnace and burners, finding no issues. * Restarted the furnace and tested for carbon monoxide in the airstream using a room CO detector placed on the vent closest to the furnace. * Performed a 2-minute test with 15 rounds, and confirmed no carbon monoxide presence in the airstream. Results: * The beeping sound from the carbon monoxide detector was determined to be an end-of-life warning, not a carbon monoxide alarm. The detector, manufactured in 2014, is nearing its 5–7 year lifespan. * Explained the different beeping patterns for low battery, carbon monoxide danger, and end-of-life warning, confirming that the detector was signaling the end of its life. * The furnace is operating normally with no carbon monoxide detecte