User's Manual
120V AC/DC Wire-in Smoke Alarm
Battery Backup 
Part Number 21006378     Model i12040
Description
The Kidde i12040 is an AC/DC powered, ionization 
smoke alarm that operates on a 120V power source 
with 9V battery backup. 
This alarm uses ionization sensing technology. Ionization 
sensing alarms may detect invisible fire particles 
(associated with flaming fires) sooner than photoelectric 
alarms. Photoelectric sensing alarms may detect visible 
particles (associated with smoldering fires) sooner than 
ionization alarms. 
Kidde strongly recommends that both ionization 
and  photoelectric smoke alarms be installed to help 
insure maximum detection of the various types of 
fire that can occur within the home. 
This smoke alarm is available in a 6-piece cut case with 
tray for easy display as well as a 6-piece bulk pack for 
contractors and property owners. This unit is a UL Listed 
product with a 10-year limited warranty.
Install Confidence
Easy Installation
•Frontbatterypulltaballowsbatteryactivationwithout
removing alarm from mounting bracket.
•Largemountingbasemakesmountingeasier,protects
surface paint from dirt and covers imperfections.
•Pre-strippedwiringharnesswitheasyoffcapdoesnot
require stripper tool. Tinned strands increase 
conductivity and wire nut grip.
Fewer Callbacks
•Onebuttondesignforeasyoperationandless 
confusion.OperatesSmartHush™andalarmtest
•Batteryrundownprotectionwillshutdownalarm 
memory when AC power is not present, reducing 
low battery chirp.
•Dustcoverprotectssensorfromcontaminatesduring
construction reducing nuisance alarms
User-Friendly Features
•Tamperresistlockingfeaturedetersalarmtheft
•AlarmmemoryflashesredLEDindicatingwhichunit
was the initiating alarm in interconnected system.
•Interconnectablewithupto24devices(ofwhich18 
canbeinitiating)includingsmoke,COandheatalarms.
Seeuser’sguideforcompleteinstructions.
 – Ionization Sensing Technology
 – One button design (operates Smart Hush™ and test)
 – Large mounting base
 – 9V Battery Backup (included)
 – Tamper resist feature
 – Alarm memory
 – Pre-stripped wiring harness with tinned strands
U
L
SIGNALING
LISTED


