Firex Mains Optical Smoke Alarm that can be interlinked with up to 23 other Kidde mains alarms, be they ionisation, optical or heat. Once interlinked, the detection of the relevant danger by an individual unit will sound across all the connected alarms. Optical alarms are for use in escape or circulation routes and in areas where there is a danger of ignition of furniture and surroundings by cigarettes producing slow, smouldering fires. This mains-powered unit should be installed by a qualified electrician and can be used throughout the home, except in the kitchen where a FIREX Heat Alarm is recommended. These alarms comply with UK Building Regulations for new housing and associated standards (Grade D BS 5839, Part 6).