The smoke alarm should be operating once fresh batteries are installed. Testing procedures: You can test your smoke alarm by pushing the Test/Hush button on the cover and holding it down for a minimum of 5 seconds. This will sound the alarm if the electronic circuitry, horn and battery are working. DO NOT use an open flame to test your smoke alarm, you could damage your alarm or ignite combustible materials and start a fire. Test your smoke alarms monthly to ensure proper operation. Erratic or low sound coming from your smoke alarm may indicate a defective alarm, and should be returned for service (refer to your warranty).