The Ei100B is an Ionisation Smoke Alarm that runs on a 9V alkaline battery (supplied with the alarm). Ionisation smoke alarms operate on the principle that electrical current flowing between electrodes in an ionization chamber is reduced when smoke particles enter. Ionisation technology gives a rapid response fast flaming fires, The Ei100B is easily installed and comes supplied with all necessary screw fixings. When the battery is first connected, the alarm may sound for 2-3 seconds – this is normal and means that the battery is connected correctly