The FireAngel CO-9D carbon monoxide detector is suitable for wall mounting or left free standing as a portable device. The detector is powered by a sealed for life battery which will power the alarm for 7 years. Featuring a digital LCD screen, the CO-9D provides an early warning of the presence of CO in your home. The digital LCD display shows low levels of CO down to 10ppm and also peak readings over the previous 4 weeks. After 7 years the alarm will alert the owner that the whole unit needs replacing. 7 year warranty.