With the Alecto SA-110 smoke detector you can go for a while. The built-in battery lasts up to 10 years. If you have confirmed the detector to your ceiling, you will not have to worry about it for the time being. The optical sensor slowly detects smoldering fires very quickly after which an audible signal of 85 dB resounds. In the event of a false report, press the time-out button. That is the same button as the test button. Test the detector regularly to make sure that the smoke alarm is working.