There's nothing more annoying than when your smoke alarm or carbon monoxide detector chirps every few seconds. This usually signals that the battery in the detector is failing and needs to be replaced. It's a good habit to replace the batteries in your smoke detectors and carbon monoxide alarms every six months during the switch to daylight savings time, but if you've neglected to do so--or perhaps used faulty batteries--replacing the batteries and perhaps a quick vacuuming is usually all it takes to stop a chirping alarm.
Remove the battery cover from the front of the alarm or, if there's no removable cover on the front of the alarm, twist it clockwise to pull it off the mounting bracket and check the back of the alarm for a battery.
Replace the battery or batteries--most alarms use 9-volt batteries, but some, particularly carbon monoxide alarms, may use AA batteries instead. If you see a place for a battery, but no battery installed, install one. The chirping should stop immediately.
Close the battery cover or, if you had to remove the entire alarm to reach the back of it, hold the alarm against the mounting bracket and twist it counter-clockwise so that it settles back into place.
Press and hold the "Test/Reset" button for three to five seconds if the chirping has not yet stopped. The alarm should sound briefly, then stop and reset. If the chirping continues, the battery or batteries you inserted may be defective; try again with another set of batteries.
Use the narrow hose attachment on a vacuum to clean the cover of the smoke alarm if chirping continues; this removes any dust that may have been triggering the alarm.