First Alert First Alert CO400 User Manual Download Page 3

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INSTALLING THE AA BATTERIES

1. Flip the battery door down to open.
2. Install both AA batteries

(included) inside the battery
compartment as indicated.
Make sure the “+” and “–”
ends of each battery are
aligned properly. A chirp 
will be issued.

3. Close the battery door.

HOW TO INSTALL YOUR CO ALARM 

Read “Where To Install Your CO Alarm” before starting.

Before you start installation,

find the pair of self-adhesive labels included

with this CO Alarm. On each label write in the phone number of your emer-
gency responder (like 911) and a qualified appliance technician. Place one
label near the CO Alarm, and the other label in the “fresh air” location you
plan to go if the alarm sounds.

IF YOUR CO ALARM SOUNDS

Actuation of your CO Alarm indicates the presence of carbon monoxide
(CO) which can kill you. In other words, when your CO Alarm sounds, 
you must not ignore it!

IF THE ALARM SIGNAL SOUNDS:

1. Operate the Test/Silence button.

2. Call your emergency services, fire department or 911. Write down the 

number of your local emergency service here:

__________________________________________________________________

3. Immediately move to fresh air—outdoors or by an open door or window.

Do a head count to check that all persons are accounted for. Do not re-
enter the premises, or move away from the open door or window until the
emergency services responder has arrived, the premises have been aired
out, and your CO Alarm remains in its normal condition.

4. After following steps 1-3, if your CO Alarm reactivates within a 24-hour

period, repeat steps 1-3 and call a qualified appliance technician to inves-
tigate for sources of CO from fuel-burning equipment and appliances,
and inspect for proper operation of this equipment. If problems are iden-
tified during this inspection have the equipment serviced immediately.
Note any combustion equipment not inspected by the technician, and
consult the manufacturers’ instructions, or contact the manufacturers
directly, for more information about CO safety and this equipment. 
Make sure that motor vehicles are not, and have not, been operating in
an attached garage or adjacent to the residence. Write down the number
of a qualified appliance technician here: 

_________________________________________________________________

Alarms have various limitations. See "General Limitations of CO Alarms"
for details.

USING THE SILENCE FEATURE

•  The Silence Feature is for your convenience only and will not 

correct a CO problem. Always check your home for a potential
problem after any alarm. Failure to do so can result in injury or
death.

•  NEVER remove the batteries from your CO Alarm to silence the

horn. Use the silence feature. Removing the batteries removes 
your protection! See “If Your CO Alarm Sounds” for details on
responding to an alarm.

The Silence Feature is intended to temporarily silence your CO Alarm’s alarm
horn while you correct the problem—it will not correct a CO problem. While
the alarm is silenced it will continue to monitor the air for CO.

When CO reaches alarm levels the alarm will sound— repeating horn pattern:
4 beeps, a pause, 4 beeps, etc. Press and hold the Test/Silence button until
the horn is silent. The initial Silence cycle will last approximately 4 minutes.

NOTE: 

After initial 4-minute Silence cycle, the CO Alarm re-evaluates present

CO levels and responds accordingly. If CO levels remain potentially danger-
ous—or start rising higher—the horn will start sounding again.

While the detector is silenced:

If the CO Alarm... 

Is silent for only 4 minutes, then
starts sounding loudly—4 beeps,
pause, 4 beeps, pause

This means...

CO levels are still potentially 
dangerous.

If the CO Alarm...

Remains silent after you pressed
the Test/Silence button

This means...

CO levels are dropping.

TO MOUNT ON THE WALL

Tools you will need:

pencil, drill with 3/16” or 5mm drill bit, 
flathead screwdriver, hammer.

1. Choose a location on the wall. Do not install the Alarm closer than 4” 

(102 mm) from where the wall meets the ceiling.

2. Hold the mounting guide template against the wall, and make a mark

inside each keyhole where you will drill your mounting hole as shown in
the diagram below.

3. Use a 3/16” (5 mm) drill bit to drill through the marks you made for the

mounting holes.

4. Insert the plastic screw anchors into the mounting holes until they are

flush with the wall. If necessary, tap them gently with a hammer.

5. Insert the screws into the anchors until the screwhead is 1/8 inch (3 mm)

away from the wall. 

6. Slide the CO Alarm onto the screws until you feel it click into place.

7. Test the CO Alarm as described in “Weekly Testing.”

“ALARM-MOVE TO FRESH AIR”

If you hear the alarm horn and the Red light is flashing, 

move everyone to a source of fresh air. 

DO NOT disconnect the batteries from the CO Alarm!

SILENCING THE LOW BATTERY WARNING

This silence feature can temporarily quiet the low battery warning “chirp” for
up to 8 hours. You can silence the low battery warning “chirp” by pressing 
the Test/Silence button. The LED will flash twice, acknowledging that the low
battery silence feature has been activated.

After 8 hours, the low battery “chirp” will resume. 

Replace the batteries as

soon as possible; this unit will not operate without battery power!

To deactivate this feature: 

Press the Test/Silence button again. The unit will

go into Test Mode and the low battery warning will resume (LED flashes and
unit sounds “chirp” once a minute.)

If you cannot silence the low battery warning, replace the batteries
immediately.

3.875 inches

Mounting Guide Template

2.5 inches (64 mm)

Summary of Contents for First Alert CO400

Page 1: ...esence of carbon monoxide gas at the sensor Carbon monoxide gas may be present in other areas The Silence Feature is for your convenience only and will not correct a CO problem Always check your home for a potential problem after any alarm Failure to do so can result in injury or death NEVER ignore your Carbon Monoxide Alarm if it alarms Refer to If Your CO Alarm Sounds for more information Failur...

Page 2: ...nd garages In turbulent air like near ceiling fans heat vents air conditioners fresh air returns or open windows Blowing air may prevent CO from reaching the sensors Outside the Mobile Home In direct sunlight This CO Alarm is designed for use inside a single family home or apartment It is not meant to be used in common lobbies hallways or basements of multi family buildings unless working CO Alarm...

Page 3: ...re Removing the batteries removes your protection See If Your CO Alarm Sounds for details on responding to an alarm The Silence Feature is intended to temporarily silence your CO Alarm s alarm horn while you correct the problem it will not correct a CO problem While the alarm is silenced it will continue to monitor the air for CO When CO reaches alarm levels the alarm will sound repeating horn pat...

Page 4: ... appliances Make sure appliances are vented to the outside Do not grill or barbecue indoors or in garages or on screen porches Check for exhaust backflow from CO sources Check the draft hood on an operating furnace for a backdraft Look for cracks on furnace heat exchangers Check the house or garage on the other side of shared wall Keep windows and doors open slightly If you suspect that CO is esca...

Page 5: ... air in the vent pipes cold humid air with extended periods between cycles Negative pressure differential resulting from the use of exhaust fans Several appliances running at the same time competing for limited fresh air Vent pipe connections vibrating loose from clothes dryers furnaces or water heaters Obstructions in or unconventional vent pipe designs which can amplify the above situations 2 Ex...

Page 6: ...ot be liable for any incidental or consequential damages caused by the breach of any express or implied warranty Except to the extent prohibited by applicable law any implied warranty of merchantability or fitness for a particular purpose is limited in duration to the duration of the above warranty Some states provinces or jurisdictions do not allow the exclusion or limitation of incidental or con...

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