The Alecto SA-100 Mini warns you when it detects smoke. The loud, 85-decibel audio signal means you don't have to worry you won't hear the alarm. The smoke detector runs on 3 3V batteries, so you can place it anywhere in the house. Since the smoke detector isn't very big, it's not an eye sore. The test button helps you check if the smoke detector is still working. That's always good to know.