How low does the battery need to get before a warning is given, and how long will the alarm keep working?

When the battery voltage drops below 3.6V, a low battery warning is given at least once every minute and the LCD displays condition D (Inadequate). After the first low voltage warning, the alarm can still continue to operate for more than 7 days. Replace the batteries with new LR6 alkaline batteries when the LCD shows condition D.