X-Series CO Alarms are optimised for use by professionals dealing with residential CO protection. They are designed to meet the needs of professional landlords and safety conscious homeowners. For increased protection, all X-Series devices can be interconnected wirelessly to form a full alarm system.When the unit detects carbon monoxide it flashes red and at the same time also gives off a loud warning. In addition, the X-Series of CO detectors from Honeywell has a neat dual-colour status light that flashes green during normal operation and flashes yellow in the event of a fault, such as almost empty batteries.