Moved into a new house and it has 3 (I think) fire/smoke alarms. There is one on each floor of the house. There is a little green light that remains on constantly and last weekend I noticed that a red light flashes about once every minute or so. Is this normal? Do I need to put batteries into these units?
You need to check the manual for the specific device but often with smoke/fire alarms a periodically blinking red light means that it's OK and when it remains steady (and beeps) the battery is dead. However it really depends on the make/model of alarm.