In most cases chirping hard-wired smoke alarms can be stopped by pressing and holding the reset button. Wait a few minutes to see if the chirping stops. If it does not, try cleaning any dust out of the alarm with a compressed air can.
Sometimes the chirping can be caused by a dead backup battery. Find the battery compartment and replace the battery with a fresh one. Press the test button for a few seconds.
If the chirping still continues, locate the home's fuse box or circuit breaker, and replace the fuse or reset the circuit that the alarm is on. If this does not stop the chirping, replace the smoke alarm.