There are a couple things you should know about your smoke detectors before you consider replacing them.
Most smoke detectors in use today use electrical wiring with a battery backup. We replace the battery most often when it starts chirping but they SHOULD be replaced every year at the same time, like on a holiday. These smoke detectors store error codes which means the chirp associated with a week battery chirp is often a common error code. Many units retain that code even after replacing the old battery. To totally eliminate that chirp you must clear the error code that is being held in memory. The best way to do that is to reset the smoke detector.
Try the following steps:
1. Turn off the smoke detector power at the circuit breaker in the main breaker panel.
2. Remove the smoke detector from the mounting bracket. Then unplug the power connector from the unit.
3. Remove the battery, usually a 9V battery from the smoke detector.
4. With the battery completely removed from the unit, press and hold the test button for 15-20 seconds.
5. Re-insert the new battery in the smoke detector and plug in the power connector.
6. Replace the smoke detector unit in the mounting bracket.
7. Turn on the smoke detector power at the circuit breaker.
When power is restored, the smoke detector should chirp once. That annoying low-battery chirping should be eliminated.
One last bit of advice: If the smoke detectors in your home are 10 years old or older, they should be replaced. Your life and the lives of your loved ones is far to precious to risk on an old smoke detector.