Kidde I9040CA Smoke Alarm, 10 ft, 85 dB, Alarm: Audio, Ionization Sensor, Wall Mounting, White

The Fire Sentry i9040 smoke alarm is a battery operated smoke alarm that utilizes ionization sensing technology. The four 4 in unit is smaller in diameter giving it discreet design with the same quality you would expect in a Kidde manufactured product. The i9040 is powered by a 9 V battery, providing continuous protection, even during power outages. This easy to install unit includes a test button to verify the detection electronics are working as intended.