Stand Alone Smoke Detector 9v Battery OperatedProduct Features:â— BSI KITEMARK & CE APPROVALâ— Photoelectric sensing technologyâ— Easy installation and maintenanceâ— Battery case at the back of a sensor for easy removal of a batteryâ— Sleek low-profile housing designâ— Low-battery warningâ— Test button verifies battery and alarm operationâ— Sounding a loud alarm signal of exceeding 85 dB in alarm mode