Chirping from a smoke detector can indicate a low battery or a problem with the power supply. Other issues may involve damage to or an obstruction in the smoke detector.
Many hard-wired smoke detectors include a backup battery and chirp if that battery is getting weak. Changing the battery for a new, fresh one should stop the noise.
If the smoke detector does not include a battery backup, check to see if the voltage going to the smoke detector is sufficient. Insufficient electric power, such as that experienced during a brown out, can cause a smoke detector to chirp. If this is the case, temporarily disconnect the power at the electrical panel until the brown out is over. Remember to reconnect the power once full electrical power is restored.
Another reason for intermittent alarms is improper wiring of hard-wired detectors. The interconnect wire (which is usually red or orange) should only be used to connect other detectors or compatible devices and should never be grounded.
According to the National Fire Protection Association a working smoke detector cuts the chances of dying in a fire by half. Call a professional to help diagnose the reasons behind a chirping smoke detector if needed.