BRK SA340B First Alert Smoke Alarm, Loudness: 85 DB AT 10 FT, Operating Voltage: 9 VDC, Operating Temperature: 40 - 100 DEG F, Environmental Conditions: Humidity: 10 - 90 PCT Relative Humidity (RH), Sensor: Dual Ionization, Dimensions: 5.6 IN Diameter X 2 IN Height, Display: Red LED, Mounting: Surfa