Kidde Worry Free 10-Year Lithium Ion Battery Operated CO Alarm with Digital Display-21009720 - The Home Depot
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Model # 21009720

Internet # 203728677

Store SKU # 151533

Worry Free 10-Year Lithium Ion Battery Operated CO Alarm with Digital Display

Kidde Worry Free 10-Year Lithium Ion Battery Operated CO Alarm with Digital Display

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

$44.97 / each


Model # 21009720

Internet # 203728677

Store SKU # 151533

Store SO SKU # 198092

Kidde 10 year Worry Free Carbon Monoxide Alarm will provide you and your family with a loud warning signal against the dangers of elevated carbon monoxide levels in your home. This alarm features a digital read-out that will provide you and your family “at a glance” real-time readings of carbon monoxide levels in your home. No more waking in the middle of the night to the dreaded midnight chirp when you install this Worry Free alarm that is powered by a ten year sealed long-life lithium battery. With this alarm monitoring your home for carbon monoxide you and your family are protected from the dangers of the silent killer, even during power outages.

  • Kidde 10 year carbon monoxide alarm is maintenance-free; never replace a battery during the alarm's operating life, in addition to the benefit of maintenance free, batteries are sealed, no need to worry about them being removed
  • Features an end-of-life signal that alerts you when it is time to replace the alarm; signal chirps every 30 - 45 seconds when alarm needs replaced
  • Money savings, no batteries to buy and replace every six months, save up to $40.00 over the life of the alarm
  • Alarm is equipped with test – reset button, tests the circuitry and horn and resets memory after alarm has sounded
  • Alarm is UL listed and is equipped with a piezoelectric horn that is rated at 85 dB at 10 ft. and electrochemical sensor that last 40% longer than other carbon monoxide alarms
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Info & Guides

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Product Depth (in.) 
Product Height (in.) 
Product Width (in.) 
Alarm Type 
Carbon Monoxide 
Alarm/Detector Features 
10-Year Battery,Digital display,Tamper Resistant 
Battery Back-Up 
Commercial / Residential 
Commercial / Residential 
Connector/Contact Type 
Power Source 
Voltage (volts) 
Warranty / Certifications
Certifications and Listings 
1-UL Listed 


Rated 4.5 out of 5 by 40 reviewers.
Rated 5.0 out of 5.0 by An outstanding CO alarm To date this has been an excellent CO Alarm. The digital display provides a clear visual indicator of any CO even if it is below the alarm threshold. I glance at the display everytime I walk by to insure the detector is still reading zero. Also, not having to worry about battery changes for ten years is a real plus. The directions are easy to follow and the CO alarm was up and running within minutes of unpacking. April 16, 2014
Rated 4.0 out of 5.0 by Easy set up Good directions, easy to install. We liked the fact it has a long battery life. Once you decide where to put the mounting bracket, you are all set! March 3, 2015
Rated 4.0 out of 5.0 by Ease of installation Great need no batteries. Need some where on the unit to mark when the installation date in order to keep up how long to monitor the system Other than that it was easy to install. February 17, 2015
Rated 5.0 out of 5.0 by Great product It was super easy to install and it looks great. Nice and s.all design. February 10, 2015
Rated 5.0 out of 5.0 by Worry Free 10-Year Alarm Institutive and easy to install and reasonably priced. October 28, 2014
Rated 5.0 out of 5.0 by Works as expected I like the fact that this CO alarm has its own battery rather than having to plug the device in and only use the batteries in the event of a power outage. December 28, 2014
Rated 5.0 out of 5.0 by WORRY FREE 10-YEAR Carbon monoxide (CO) ALARM WITH DIGITAL DISPLAY This Carbon Monoxide (CO) Alarm with digital display it comes equipped with a sealed lithium battery and ready to operate for up to 10 years of battery life and worry free service. It looks good and easy to install. make sure you have at list one of this or any CO detector in your house at all time and in a good working condition, and I am not just whistling dixie! JUST DO IT! March 28, 2014
Rated 5.0 out of 5.0 by Have several of their products and never disapointed Accurate, easy to use and understand. I am a volunteer firefighter and have seen several brands in homes on CO alarm calls. Kidde products seem to be more accurate, compared to our detectors, last longer, and have least amount of problems. April 15, 2014
Rated 5.0 out of 5.0 by Actual Exposure...It Works! I bought this unit 8 months ago after a potentially deadly exposure in our six unit apartment building. A few of our previous CO detectors in several of the apartments gave the dead battery signal instead of an alarm so no one was alerted. We ended up being evacuated by the fire department in the middle of the night and one person going to the hospital! I did a good deal of research, bought this unit and have felt much safer. Just last week we had another brief exposure as our gas water heater had a leak in the flue. There was not enough CO to set off the alarm, but the detector window showed 13 ppm, less than the 30 ppm to set off the alarm, but the fact that the detector worked as advertised, even if 13 ppm is not dangerous, is still very reassuring to me. I have recommended this product to all of my friends and family. The sealed 10 year battery is a real plus. I have it mounted at eye level in my kitchen, which is nearest to the boiler room and the enclosed garages. I can check and test it often and easily. December 4, 2014
Rated 5.0 out of 5.0 by So far so good! Excellent battery life, and so far no false alarms. December 10, 2014
Rated 5.0 out of 5.0 by Willing to pay the additional $10 to have the digital readout Before purchase I checked with our county fire dept. to obtain an appraisal of Kidde products and the CO detector. The officer wasn't familiar with a particular model of CO detector but gave Kidde high marks overall. He reinforced the need to have a CO detector in your home if CO can be generated by a furnace, water heater, stove, fireplace, etc. The true test of quality and value is the alarm if CO exceeds the threshhold. Fortunately ours has not. The digital readout is working though I don't have a meter to test its accuracy. Still, there's a comfort to have the readout. April 3, 2014
Rated 5.0 out of 5.0 by Does the Job Purchased two of these units from HD a couple of months ago, and so far, no complaints. The installation was easy. I like the fact that the operation is independent of household current; they work when there's a power outage. This is important to me because I run a portable generator. Also, with the lithium ion battery installed, I will never have to worry about battery replacement. Yes, they cost a bit more, but to me it was worth it. October 23, 2013
Rated 5.0 out of 5.0 by Simple! Simple to set up and install. As a family man and a firefighter, I think it's definitely worth the extra money due to the peace of mind for the next 10 years. June 17, 2014
Rated 5.0 out of 5.0 by Replacement Carbon Monoxide Detector Bought this to replace a dead CO detector. Big advantage is that you don't need to locate it at a power source! compact, yet fully featured and very easy to wall mount, where you want to. June 10, 2014
Rated 5.0 out of 5.0 by No worry ease of mind Luckily we haven't had to test our alarm out, but we are happy with the design and easy of installation. We just installed the included batteries, and placed in our hallway right outside the heater room as that is the only place we have gas in the house. The price is absolutely worth the peace of mind, especially with our first baby on the way. May 10, 2014
Rated 5.0 out of 5.0 by Works well It works well, it is compact and does not look odd in a room. October 23, 2014
Rated 5.0 out of 5.0 by Peace of mind Bought this for our granddaughter's bedroom just to be safe. October 23, 2014
Rated 5.0 out of 5.0 by So far so good. Will tell you more in 10 years. This one seems to be well worth the money. The battery does not need to be changed at all and should last 10 years. On two prior occasions a device like this has saved our lives. The fire box burned out in the furnace and once a pipe had become disconnected at the furnace. Both times, we left the house, called the fire dept. and sure enough the house was filled with carbon monoxide. February 4, 2014
Rated 4.0 out of 5.0 by Great concept I really like the concept of a product that's designed to last 10 years without any battery changes. The only thing the user needs to do is vacuum occasionally, and test. The digital readout with memory recall is also convenient. Installation was easy: the screws and drywall anchors were provided. I like that the unit switches on when the unit is mounted on the back cover. The two things that prevented me from giving this product 5 stars concern the back cover. First, the instructions for removing the back cover are on the inside of the back cover where they are totally inaccessible and useless once the cover is installed. Second, if the drywall screws are tightened too tight during installation, the unit can't be removed from the wall without ripping the screws out of the wall. May 30, 2014
Rated 1.0 out of 5.0 by Malfunctioning on day 2 Installed in hallway where recommended using wall mount. On day 2 I get a call from wife that the thing is going off with readout of 50ppm-53ppm. There is no off switch. Once home I moved it outside and the thing just kept going off with same ppm displayed. I taped over the sensor, and same thing. It is broken and will replace with another model/brand. June 24, 2013
Rated 5.0 out of 5.0 by I like the digital display Install instructions were clear. The display gives me confidence especially for a gas one cannot see or smell. I'm hoping it stays close to zero, never gets needed, and lasts 10 years July 15, 2014
Rated 5.0 out of 5.0 by Great little Alarm Bought one of these for the boat.I have a built in but I wanted another detector to put in the sleeping area. It has never gone off, but I do test it and i have even stuck it in front of the generator exhaust and i can see the PPM read out changing. July 16, 2013
Rated 5.0 out of 5.0 by Easy to install, long battery life, no maintenance. CO alarm was easy to install, with a large read-out. Outward appearance and size is that of a wall central air thermostat. The portable feature allows you to check other areas with the same alarm. Nice feature! June 11, 2014
Rated 5.0 out of 5.0 by Carbon Monoxide Alarm Original lasted the predicted 7 years and was pleased with the brand and service (alarm went off once with good reason). Stay with a proven alarm. May 13, 2014
Rated 5.0 out of 5.0 by Helps me feel safer I installed this unit about a month ago. 1st of all it was ez to install, just a few minutes, and 2nd it gives me peace of mind that my family is protected! Its a no brainer! May 10, 2014
Rated 5.0 out of 5.0 by This device is small and you can put it in a unconpicuos place. I like this device because it is small and you can put it anywhere even on a table. We live in the country and use propane heat, this device makes me feel safe in the coldest weather. It is not hardwired but has a battery that will last 10 yrs. (no holes in my wall). March 30, 2014
Rated 1.0 out of 5.0 by Is there less than 1 star? Never worked right out of the box. After the battery was activated, it tested fine. Three days later it starts to beep intermittantly. Display never read anything. April 8, 2014
Rated 5.0 out of 5.0 by Great! I like that it doesn't take up an outlet. Great that it can either be wall mounted or sit on a surface. Definitely recommend. March 25, 2014
Rated 4.0 out of 5.0 by Easy to use and great features Only time will tell if it lasts 10 years but changing batteries is getting old and expensive. It is however a little pricy but if it ever has the opportunity to save my life it is really a cheap investment March 15, 2014
Rated 5.0 out of 5.0 by great product, i love that the battery last for 10 years I would recommend this product to everyone. I like the fact that its battery operated for 10 years, don't have to worry about plug in and replacing the battery, etc. March 12, 2014
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