If the problem persists, replace the smoke alarm immediately. Enclose a note in the package describing what is wrong with the unit. Recently the safety standards for how the alarm horn sounds during an alarm were changed. Smoke alarms manufactured before 1998 sound continuously during an alarm. It is important that all family members learn to recognize the sound all the smoke alarms in your home make.
Smoke alarm sounds when no smoke is visible.
The smoke alarm may be dirty. Gently clean the smoke alarm as indicated in your user's manual. Check the location of the smoke alarm. Clean the smoke alarm, then try re-installing it a few feet away. Air streams near kitchens, for example, can pull cooking smoke into the smoke alarm.