If you have an alarm that warns you only every 30 minutes, spend a little and get new alarms A 30 minute interval is bad design, mine are like 30 seconds to 1

If you have an alarm that warns you only every 30 minutes, spend a little and get new alarms A 30 minute interval is bad design, mine are like 30 seconds to 1 minute (been a while) plus they have a yellow LED when battery is low, red when dead or removed, and green when all systems go