Kidde 0914E Fire Sentry Battery Operated Smoke Alarm, 85 DB At 10 FT Loud, 9 VDC Operating, 40 - 100 DEG F Operating, Environmental Conditions: Up To 85 PCT Relative Humidity (RH), Ionization Sensor, Dimensions: 4 IN Diameter X 1.45 IN Depth, Mounting: Wall Or Ceiling, Sensitivity: 0.52 - 1.12 PCT/F