What Does It Mean When A Smoke Detector Blinks Red?

A blinking red light on a smoke detector can mean several things: normal operation (periodic blink), low battery, a need for testing, dust/debris in the sensing chamber, end of life (replace after ~10 years), or actual smoke detection (usually with loud beeps). Check the manual for model-specific meanings, clean and test detectors monthly, replace batteries regularly, and replace detectors around 10 years. Resetting by holding the test/reset button or removing power/battery can clear some persistent red lights.