Ionized alarms and photoelectric technology alarms work slightly differently. Ionization technology tends to be better for detecting small particles, which are common in flaming fires. Photoelectric technology is generally better for large particles, like the kind you get in a smoldering fire. Both types generally warn you if they aren't working properly. They chirp, or go-off for no apparent reason. Even hard-wired alarms can run into battery power problems, because they have backup batteries in them.
Check the red light emitting diode (LED) on the face of the unit. It flashes in patterns depending on the event the device wants to report. If the red LED flashes once a minute and the device chirps once a minute, it's telling you the battery is low or missing.
Check the LED again. If the red LED flashes rapidly and the horn pattern is three beeps followed by a pause, and then three further beeps followed by a pause, then the alarm has sounded. The unit with the rapidly flashing LED and the horn is the one that triggered the alarm, false or not. This condition requires your attention, don't ignore it. Verify it's a false alarm and not an actual fire.
Clean the unit if you experience continual false alarms. You can also try relocating the alarm. Avoid air streams near kitchens; keep it at least twenty feet from furnaces and water heaters. Keep the alarm away from very damp or humid areas like near bathrooms, and away from dusty, dirty or greasy areas, and also away from drafty areas.
Make sure power is supplied to the unit. Press the Test/Silence button on all the alarms periodically. Hold it down and verify the horn sounds.