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Page 2 of 2 August 2008
Troubleshooting Guide
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Smoke Alarms
Smoke Alarms • Carbon Monoxide Alarms • Heat Alarms • Fire Extinguishers
Smoke Alarm Troubleshooting Guide
for Contractor and Builder Service Managers
Why do smoke alarms chirp intermittently?
The "chirp" will only be caused by issues surrounding the battery or miss wiring. However, a
homeowner may confuse the chirp with an intermittent alarm. Try and get the homeowner to be
specific as to what they are hearing. A “chirp” will have a higher pitched tone and sound in equal
intervals about once every minute. An intermittent alarm will be random, sound usually for several
seconds and have a lower pitched tone. Any of these situations can cause unwanted chirps:
• Battery pull-tab is still in the alarm.
The battery pull-tab must be removed after AC power is
provided to the alarm.
• The Battery Drawer is open.
The battery drawer must be completely closed for the
battery to make contact with the terminals.
• Low battery.
As the battery in a smoke alarm becomes weak,
the smoke alarm will "chirp" about once a
minute to alert you that the battery needs to be
replaced. Note: Only the alarm with a low
battery will chirp. No signal is sent through the
interconnect wire. The other alarms will be
silent.
• Tip for Facility Managers.
During the moving season, inform Facility
Managers who maintain apartment buildings that if
they are shutting down power to unoccupied apartment
units, to be sure to open the battery drawer on alarms to
keep the battery from draining. Remind them that if they restore
power temporarily (e.g. to show the unit) the alarm will chirp if the drawer is open. The alarm
now thinks there is no battery. This is also important for single-family houses that will be
unoccupied for extended periods.
• Battery is present but part of the terminal is obstructed.
The battery may not be fully making contact with the terminals in the alarm. Check to be sure
the battery pull-tab or some other obstruction is completely removed.
• A different device or appliance.
Security systems, monitors, carbon monoxide alarms, and other devices have similar low
battery or alert signals.
• How long will a battery last in a smoke alarm?
A fresh carbon zinc battery in the 9120B will last up to one year; depending on how fresh it
was before it was installed and when it was activated. UL 217 mandates that the battery in a
backup mode only need to last for 24 hours in standby condition and thereafter be able to be
in alarm for at least 4 minutes. As a rule of thumb in smoke alarms, alkaline batteries will last
for about 1-2 years and Lithium batteries for 6 years plus.
The SC9120B battery will last for about 20 to 30 days. UL 2034 states that the battery should
last for 7 days in standby condition and thereafter be able to be in alarm for at least 4 minutes.
• Why does the alarm chirp when power is disconnected and the battery is removed?
The circuitry of the alarm contains capacitors that store energy. You must press and hold the
test button to dissipate the capacitor. You will hear a steadily weakening sound until it is silent.