Reddit reviews Kidde i9030 FyreWatch Battery-Operated Smoke Alarm

Test button checks horn, battery and alarm circuitryLow battery indicator warns when battery needs replacementTamper resist locking pin ¿ helps deter theft or tamperingBattery operated, 9 Volt battery included (best with Polaroid 9 Volt batteries)Kidde’s smoke alarms meet the requirements of Underwriters Laboratories (UL), an independent facility that tests products for compliance with widely-accepted safety standards