The following table illustrates the possible digital displays, describes the
audible alarm patterns, and the recommended actions to take.
Operating and Alarm Characteristics
LED Display Shows
Alarm Sound
Unit Status
Recommendation
Brief “888” along with
any number between 100
and 300.
4 quick beeps,
5 seconds
silence,
repeated once
Self checking when AC
powered (Test button
was pressed or unit
was first powered)
None – CO has not been
detected. Numbers
shown for test purposes
only
Steady “0” displayed.
None
Normal AC operation
(sensing no CO) and
with a good battery
None
A display of CO
concentration from 30-999.
4 quick beeps,
5 seconds silence,
repeating
Alarm condition.
Dangerous concentrations
of CO detected
Refer to “What to do
When the Alarm Sounds”
(inside front cover)
“Lb” flashes
alternately with
any number.
One quick beep
every
15 seconds
AC powered and low
or missing
battery
Install or replace 9V
battery
Steady “Err “displayed
One quick beep
every 30 seconds
Unit malfunction
Replace battery.
If “Err” continues, unit
has malfunctioned.
Replace immediately.
Unit will not respond CO
No display alternating with
display of CO concentration
every 60 seconds.
4 quick beeps,
5 seconds
silence, repeating
every 60 secs
Alarm condition
powered on battery
backup. Dangerous
concentrations of CO
detected
Refer to “What to do
When the Alarm Sounds”
(inside front cover).
Replace battery
No display alternating with
“0” every 60 seconds.
None
Normal operation after
first 4 minutes of 9 V
battery operation. Unit
monitoring for CO
Verify AC power is
restored as soon as
possible to conserve
battery. Replace battery
7. The 900-0234 (with digital display)
Operating Characteristics
Whenever the 900-0234 is operating, the digital display will display “0” to
indicate the unit is monitoring for CO. If the alarm senses dangerous levels
of CO, the digital display will indicate the CO concentration in parts per
million (PPM), and the alarm will emit an audible alarm pattern. This alarm
will display a “0” if CO concentrations between 0 and 30 PPM have been
detected within the last 15 seconds.
When the unit is first powered up, the digital display will show three
“eights” – indicating the alarm is in the start-up mode. The three “eights”
will remain for approximately 20 seconds. After 20 seconds, the alarm
should display “0” and begin monitoring the air for CO and will continue to
do so as long as it receives power.
“End” displayed.
Red LED flashes
every 30 seconds
One quick
beep every 30
seconds
End of unit life
Replace unit immediately.
Unit will not respond to CO
