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Internet # 205423758

Model # 21029713

Store SKU # 1000392353

Firex Plug-In Carbon Monoxide Detector, AA Battery Backup

$31.97
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  • Carbon monoxide detector plugs directly into wall outlet
  • AA battery backup for protection even during power outages
  • Alarm will sound when dangerous levels of CO are detected
  • View More Details
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Pay $6.97 after $25 OFF your total qualifying purchase upon opening a new card. 
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Product Details

About This Product

Kidde AC/DC carbon monoxide alarm plugs directly into your home's standard wall outlet. The AA battery backup provides protection even during power outages when many CO incidences occur. Tamper resist feature deters tampering or theft of the unit.

Highlights

Product Information

Internet # 205423758

Model # 21029713

Store SKU # 1000392353

Specifications

Dimensions

Product Depth (in.)

1.5 in

Product Width (in.)

2.75 in

Details

Alarm/Detector Features

Battery Back-Up

Alert Type

Siren

Battery Type Required

9-volt

Commercial/Residential

Home

Included

Batteries

Pack Size

1

Power Source

Plug-In

Returnable

90-Day

Voltage (V)

120

Warranty / Certifications

Certifications and Listings

UL Listed

Questions & Answers

Confused......description shows AA Batteries in one section and 9 Volt Battery in another. Which is it ?
ByApr 23, 2026
0 Answer | 
Answer This Question

K have a middle cafnoo oxide uh in. If was laying on the floor face down. There was a high pitched sound coming out of it. I picked it up and it’s quiet. Any i1
ByMar 26, 2026
1 Answer | 
Answer This Question

Hello. it sounds like the tamper resist feature was activated on this alarm. The tamper resist is an optional feature and DOES NOT need to be activated for the CO alarm to function properly. The Tamper Resist feature is a constant 85dB alert to indicate the unit has been unplugged or has come loose from the outlet. THIS FEATURE IS INITIALLY DISABLED FROM THE FACTORY AND MUST BE ACTIVATED IF FEATURE IS DESIRED. To activate the tamper resist feature: The tamper resist button is the T shaped button on the back of the alarm. The Tamper Resist Slide is in the rectangular hole under the T shaped Tamper Resist button. Move the tamper resist activate slide to the “ON” position. Once enabled, there is a two minute delay when power is supplied to give you time to plug in the unit after activating the batteries. This feature is automatically disabled once the battery voltage has reached a level to cause a low battery warning chirp. Pressing the Test/Reset button will defeat the 85dB tamper alarm for two minutes to allow time for the batteries to be changed without the alarm sounding. To deactivate the tamper resist feature, press in the tamper resist activation switch and move the activate slide to the “OFF” position.

By|Mar 26, 2026


    At what number does the monitor start beeping as an alert I was told that it should be lower much lower than 70 because that 70 is a problem, but it lowered between the fortyish area you start not feeling well. That’s the best time to get it checked.
    ByMar 18, 2026
    1 Answer | 
    Answer This Question

    Hello. Carbon monoxide effects depend on both concentration and exposure time. At 70 ppm, symptoms are uncommon for most healthy adults, though one to four hours of exposure may lead to mild headache or fatigue. At 150 ppm, 10 to 50 minutes of exposure may result in headache or dizziness. At 400 ppm, symptoms can develop within minutes and can become serious with continued exposure. UL 2034 residential CO alarms are designed around these time-and-concentration ranges, sounding within these windows to warn occupants as exposure levels increase. (U.S. Consumer Product Safety Commission). This unit conforms to UL 2034 standards. At 70 parts per million parts of air, PPM, it will go off after 1 to 4 hours of continuous exposure. At 150 PPM, it will go off after 10 to 50 minutes of continuous exposure. At 400 PPM or higher, it will go off after 4 to 15 minutes of continuous exposure.

    By|Apr 1, 2026

      (1)

      What ppm does this alarm go off?
      ByMar 2, 2026
      1 Answer | 
      Answer This Question

      Hello. This unit conforms to UL 2034 standards. At 70 parts per million parts of air, PPM, it will go off after 1 to 4 hours of continuous exposure. At 150 PPM, it will go off after 10 to 50 minutes of continuous exposure. At 400 PPM or higher, it will go off after 4 to 15 minutes of continuous exposure

      By|Mar 20, 2026

        (1)

        How many ppm for alarm to sound?
        ByMar 1, 2026
        2 Answers | 
        Answer This Question

        The ppm is in the attached picture

        By|Mar 10, 2026

          Hello. This unit conforms to UL 2034 standards. At 70 parts per million parts of air, PPM, it will go off after 1 to 4 hours of continuous exposure. At 150 PPM, it will go off after 10 to 50 minutes of continuous exposure. At 400 PPM or higher, it will go off after 4 to 15 minutes of continuous exposure

          By|Mar 9, 2026


            How many ppm before detector goes off
            ByFeb 27, 2026
            1 Answer | 
            Answer This Question

            Hello. This unit conforms to UL 2034 standards. At 70 parts per million parts of air, PPM, it will go off after 1 to 4 hours of continuous exposure. At 150 PPM, it will go off after 10 to 50 minutes of continuous exposure. At 400 PPM or higher, it will go off after 4 to 15 minutes of continuous exposure

            By|Mar 9, 2026


              Does this model have a cord included so I can place detector higher than at the wall outlet/
              ByFeb 16, 2026
              1 Answer | 
              Answer This Question

              Hello. No, it doesn't. You would want the KN-COPP-3 instead.

              By|Feb 19, 2026


                Chirping/battery change. We couldn't find the instructions so we didn't press & hold the reset button. We pressed it once without holding. lt made the expected reset sounds and the light is green. Does that mean it's working or should we press & hold? TY!
                ByNov 14, 2025
                1 Answer | 
                Answer This Question

                Hello. Pressing and holding the button on this alarm will not have any function. If you have changed the battery and tested the alarm and the alarm is not chirping for error mode or low battery and it goes through the test cycle properly, it should be fine. Feel free to call us with the alarm in hand at 1-800-880-6788

                By|Nov 17, 2025


                  Viewing 1-8 of 78

                  Customer Reviews

                  4.7 out of 5

                  • 4.7 out of 1,725 reviews
                  • 95% recommend this product
                  Filter by:
                  Showing 1-10 of 1,725 reviews
                  Easy to install and not too bright that it affects your eyes when looking up at them. Bright when needed and easily dimmable!
                  by
                  Response from Kidde ExpertMar 23, 2026
                  We're glad to hear that the product is working great for you!
                  Don’t rely on these products, trust your nose and gut
                  I’m giving this alarm 2 stars because I don’t think I have this exact model but I am so upset with Kidde and there products right now. I have been smelling a gas/propane/cabbage smell in my home and have had their carbon monoxide/gas detector plugged in above my stove for months and it has never gone off. Tonight I got nervous when a family member came over and said the smell was overwhelming while I was preheating stove. I called my gas company and they came over and found the safety was broken on the valve in my kitchen and has been leaking gas and carbon monoxide when lit…. The valve was “red tagged” until it can be fixed and the kidde detector never went off.
                  by
                  Response from Kidde ExpertSep 15, 2025
                  Hi Hai, thank you for taking the time to share your experience with us. Your concerns are important to us, and we'd appreciate the opportunity to discuss them in more detail. If you haven’t already, please give us a call at 1-800-880-6788 or email Kidde.Product.Support@carrier.com, so we can take a closer look at what's going on.
                    1 found this review helpful
                    Simple installation - just plug in. Uses everyday batteries. Decent price.
                    by
                    • Verified Purchase
                    Alarm died after 1 month-
                    So I am a smoke alarm enthusiast and I collect smoke & carbon monoxide alarms & just today my Kidde KN-COB-DP2 just died on me, it did not even give the end of life signal. I expect at least ok quality from y’all but nope I get this- I will be replacing this with a First Alert carbon monoxide alarm that has better quality.
                    by
                    Response from Kidde ExpertJul 20, 2022
                    Hello. Died how? If you have issues with our alarm, please call us at 1-800-880-6788 with the alarm in hand before you replace it. We do stand behind our products and we are happy to troubleshoot and figure out what is going on and get an issue resolved.
                      6 found this review helpful
                      I “Kidde” You Not…!
                      Great Value & Easy Install
                      by
                      • Verified Purchase
                      • Recommended
                      Very nice, great price good quality & looks like. Was easy to set up.
                      Very nice, great price good quality & looks like. Was easy to set up.
                      by
                      • Verified Purchase
                      • Recommended
                      1 found this review helpful
                      Super easy, not really an install. Pulled tab, inserted 2 AA batteries and plugged into wall. As ...
                      Super easy, not really an install. Pulled tab, inserted 2 AA batteries and plugged into wall. As long as light is green, I'm good. Will sound alarm if there's any danger. Super easy, super happy!
                      by
                      • Verified Purchase
                      • Recommended
                      4 found this review helpful
                      Ready to use out of the package. Simple installation. AC operation plus battery backup. Unit h...
                      Ready to use out of the package. Simple installation. AC operation plus battery backup. Unit has a 10 year life span. Previous unit alerted end of life operation at 10 years and 1 month as designed. Unit is installed in a finished 2nd floor garage studio. Previous unit detected CO from backup generator running outside of garage at ground level. I trust the Kidde CO monitor. Based on experience with previous Kidde CO monitor, this unit should be fine.
                      by
                      • Verified Purchase
                      • Recommended
                      3 found this review helpful
                      Plugging in a few of these into wall outlets at...
                      Plugging in a few of these into wall outlets at strategic locations around your home, especially close to sleeping areas where they can be heard if the unthinkable happens, is probably the quickest and most effective route to high stakes peace of mind you can do for your precious family.
                      by
                      • Verified Purchase
                      4 found this review helpful
                      Lightweight and very depenable
                      Lightweight and very depenable
                      by
                      • Verified Purchase
                      • Recommended
                      1 found this review helpful
                      Showing 1-10 of 1,725 reviews

                      Compare Key Features

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                      Product Snapshot

                      Ideal for homeowners looking for battery backup and tamper resistance, ensuring safety during power outages.
                      Ideal for homeowners needing reliable CO detection with digital display, 85dB alarm, and 10-year lifespan.
                      Ideal for homeowners needing interconnected CO safety with battery backup and digital display. Ensures comprehensive protection during power outages.
                      Ideal for homeowners needing reliable CO detection with digital display, 10-year battery, and tamper-resistant design for peace of mind.

                      Detection Technology

                      Electrochemical
                      Electrochemical
                      Electrochemical
                      Electrochemical

                      Power Source

                      Plug-In, AA Battery Backup
                      Battery
                      Hardwired, Battery Backup
                      Battery

                      Battery Backup

                      Digital Display

                      Interconnectivity