The best time to change a smoke detector battery is on a scheduled date that can easily be remembered and will prompt you to do so. A great idea is to replace your smoke detector batteries annually when you either set your clock ahead or forward for Daylight Savings Time. There may be other operating indications and signs that the battery is not good, alerting you there is a need to change.
If your detector makes a chirping, bird-like noise, test it first and replace the batteries. The chirping sound should be a detector alert the batteries are not charged enough. The other cause might be loose wires if the unit is wired through your house power. There may be dead insects around the sensors so try vacuuming in and around the smoke alarm, or you can try using a can of compressed air to blow debris out and away. If changing the batteries and cleaning does not work, you need to replace it.
If you hear no sound when smoke is present, test the unit and replace the battery. If there still is no sound when smoke is present, you probably have a bad sensor or sounding device. Smoke detectors are relatively inexpensive but replacing component parts like a sensor, alarm or alert sounding device is not a financially prudent move. You would save money buying a replacement unit. If the detector sounds an alarm when there is no smoke, say for example in a hallway off the kitchen, you need to make sure it is more than 20 feet away from your stove and oven. Try replacing the battery first. If it is near a furnace, bathroom or utility room, you also should relocate it at least 10 feet away. If these suggestions do not work, you need to replace the unit.
Wireless detectors use three “AA” batteries and operate both the single device alert signal as well as communicate with other devices in the home connected to the same configuration. Each individual device needs to be tested weekly mostly to confirm it is communicating with all other devices. There are factors that will inhibit the communication performance for each individual unit that may have nothing to do with the batteries. Sometimes other devices nearby that operate on an RF (radio frequency) signal will interfere with your wireless smoke detector. Conduct a battery test to make sure you have full power. If the battery checks out, it is not a power problem and you will more than likely need to re-set the system ID.
Event Initiated Change
If there is a smoke or fire in your home that prompts your smoke alarms to sound, everyone should exit quickly. The detector alarm will continue to sound until it is re-set, so if you vacate the premises for an extended period of time, you will more than likely need to change the batteries in all detectors that sounded. Make sure when reoccupying the building you test each battery and make the necessary replacements.
Always use high-quality brand name batteries for your smoke alarm.