The ELRO Mini FC4510 is a carbon monoxide detector. Carbon monoxide is a deadly gas that you do not smell, taste, see and feel. Place the alarm in the vicinity of your boiler and you will be notified in good time. The built-in lithium battery lasts up to 10 years. It is important to test the alarm regularly (on average once a month) via the test button. That way you can be sure that the reporter really works.