Hikfire HF-S3E Standalone Smoke Detector, With dual light sensing technology, effectively reduce misreports caused by water vapor environment, which is more accurate for smoke sensing alarm, Support smoke alarm, Support local 85dB high decibel alarm sound, Lithium battery power supply, With self-testing feature, user can check the device working status by self-test button, Multiple failure alarm features, including low voltage alarm and maze fault alarm, Power supply: 3 V DC, battery CR123A(replaceable), Battery capacity: 1600 mAh.