Kidde Battery Operated Ionization Smoke Alarm-21008051 - The Home Depot
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Model # 21008051

Internet # 100051755

Store SKU # 182262

Battery Operated Ionization Smoke Alarm

Kidde Battery Operated Ionization Smoke Alarm

This item has been discontinued.
The Home Depot no longer carries this specific product.

$4.98 / each


Model # 21008051

Internet # 100051755

Store SKU # 182262

Store SO SKU # 198092

The Kidde i9040 Battery-Operated Ionization Smoke Alarm is a single-station alarm with an early warning signal. This alarm utilizes ionization sensing technology to activate in the event of a smoke or fire incident and its compact, 4 in. design lends it a discreet profile in your home or business. Powered by a 9-Volt battery, this smoke alarm will protect you, your family and home during a power outage. When the battery begins to lose power, a low-battery alert will begin to chirp to notify you it is time to replace.

  • Utilizes ionization sensing technology to detect smoke or fire
  • Provides an early warning signal in the event of a smoke or fire incident
  • Wireless technology for easy installation
  • Low-battery indicator chirps to alert you to change the battery
  • Test button tests the unit's electronic circuitry, horn and battery function
  • Battery power means protection during power outages
  • 9-Volt battery included use Kidde power supply (205976052)
  • Compact design for a low-profile presence
  • Note: product may vary by store

Info & Guides

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Product Depth (in.) 
Product Height (in.) 
Product Width (in.) 
Alarm Sensor Type 
Alarm Type 
Alarm/Detector Features 
No Additional Features 
Commercial / Residential 
Commercial / Residential 
Connector/Contact Type 
Power Source 
Voltage (volts) 
Warranty / Certifications
Certifications and Listings 
1-UL Listed 


Rated 4.3 out of 5 by 25 reviewers.
Rated 5.0 out of 5.0 by It could save your life! I purchased these on an impulse buy. I was walking down the water heater isle and saw these at such a great price. I figure I should pick up a few and install them throughout the house. I install them that weekend and forget about them. A few months later, I'm in my bedroom and I hear a loud beeping coming from downstairs. I go to investigate and find my living room full of smoke. The smoke was caused by frayed wires on a home entertainment system. If it wasn't for this alarm, the smoke would go unnoticed leading to an actual fire. At this price, I would say to buy one for your friends and relatives as well. There aren't many gifts that you can give that can save someones life. April 10, 2013
Rated 5.0 out of 5.0 by Do the job - I think. Easy install with batteries included. Great value. May 26, 2015
Rated 1.0 out of 5.0 by Battery Life Poor Purchased these units and installed them. The factory supplied batteries started chirping lasted only 3 months. Literature says 6 month recommended replacement. Replaced batteries with Duracell MN1604 which is the best recommended by the manufacturer. These batteries are also lasting only 3 months and began chirping, a hassle! Going to throw them out and buy a different brand! February 5, 2015
Rated 5.0 out of 5.0 by Nice! A no frills smoke alarm that installs in just a couple of minutes and has a great price. I got this for our camper and it's perfect. A little smaller than the old one and it comes with a battery as well. Awesome value. June 28, 2014
Rated 4.0 out of 5.0 by Good Deal The Smoke Alarms were a good deal, there are 2 for a great low price! May 12, 2015
Rated 5.0 out of 5.0 by Excellent value I have installed more than 10 of these in several locations and they have been in service for over a year now. These run on single 9V battery which is included with the package. These are UL listed so meet the required standards. I really don't see the point in buying the more expensive ones unless you need dual power supply i.e. the 120V and 9V. July 16, 2012
Rated 4.0 out of 5.0 by Size doesn't matter. The description clearly states "compact design". It works just as well (maybe better) as larger units but requires less space to install. It's a smoke detector, not a manhole cover. I have several of these in my home and have no complaints. They are easy to install and maintain. Battery life has been satisfactory. No surprises. January 12, 2014
Rated 5.0 out of 5.0 by Great replacement for older smoke alarm Pickup them up at the customer service desk. Thanks for making this purchase so easy. April 10, 2015
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