Kidde Battery Operated Ionization Smoke Alarm-21008051 at 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
Bulk Price Discount Available
This item qualifies for a bulk price discount
if you purchase at least 6 units. The
adjusted price will display in the Cart.


Model # 21008051

Internet # 100051755

Store SKU # 182262

Store SO SKU # 198092

The UL-listed Fire Sentry 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
  • Compact design for a low-profile presence
  • Ideal for the home or business
  • UL listed
  • Note: Product may vary by store
  • Note: Product may vary by store.

Info & Guides

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Alarm Sensor Type  Ionization  Alarm Type  Smoke 
Alarm/Detector Features  No Additional Features  Assembled Depth (in.)  4 in 
Assembled Height (in.)  1.5 in  Assembled Width (in.)  4.0625 in 
Certifications and Listings  1-UL Listed  Commercial / Residential  Commercial / Residential 
Connector/Contact Type  None  Included  Batteries 
Voltage (volts) 


Rated 4.4 out of 5 by 16 reviewers.
Rated 5 out of 5 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 5 out of 5 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 4 out of 5 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 out of 5 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 5 out of 5 by Good value/quality Picked up one of these today for a bedroom in a small 3 bedroom (occupant sleeps with door closed) ranch house today. It currently accompanies two First Alert units in the beginning/end of the hallway (photoelectric near kitchen/livingroom and ionization at the end towards the 3 rooms). This smoke alarm is just as well built as any comparable First Alert and has a small footprint while being lightweight which makes it a perfect candidate for a ceiling mount unit. The installation was cake, drill two holes, mount the bracket, and make sure battery is installed and away you go! While being a basic/entry level smoke alarm it has some decent features such as a hush button, a safety tab mechanism that insures the battery is installed (or unit will not lock into bracket), and my personal favorite an led that blinks every 40 seconds to insure the unit is receiving power. At 5 dollars, this is a very solid smoke alarm that just works. I would recommend this to anyone looking for a basic ionization smoke alarm to supplement other units for added safety. July 2, 2012
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Store Exclusive. This item is available for purchase in select stores only.