Change the batteries. Twist the alarm counterclockwise, disconnecting it from its ceiling mount and pry off the battery cover. Remove the three AA batteries or single 9V battery and install fresh replacements. Replace the cover and twist the alarm clockwise back onto its ceiling mount. Kidde alarms emit a chirp once every minute when the batteries are low.
Move the unit to a new location; electrical interference could be causing problems with your alarm. Keep your alarm out of tight corners or the very top of pitched ceilings for best smoke detection. False alarms from cooking smoke may briefly trigger the alarm causing a chirping sound if the unit is poorly positioned.
Replace the unit. Some Kidde smoke alarms chirp every 30 seconds once 10 years have passed from the initial start-up indicating the unit should be replaced. The "Alarm Replacement" chirps cannot be canceled and are designed to encourage purchase of a replacement that will safely protect your home.