features: Combination Smoke and Carbon Monoxide Alarm Loud voice alarm warning system TELLING you if smoke or carbon monoxide has been detected. This eliminates confusion as to whether it is a smoke or carbon monoxide (CO) danger. This Kidde 0122UK has extra sensitive state-of-the-art electrochemical technology for carbon monoxide detection with ionisation technology for smoke detection. Ionisation alarms are quicker at detecting fast flaming fires so giving you a faster response time.