--- product_id: 2536037 title: "First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack" brand: "first alert" price: "€ 45.02" currency: EUR in_stock: true reviews_count: 13 category: "First Alert" url: https://www.desertcart.hr/products/2536037-first-alert-co400-carbon-monoxide-co-detector-battery-operated-alarm store_origin: HR region: Croatia --- # Advanced electrochemical sensor for precise CO detection Loud 85dB alarm ensures immediate alert 9V replaceable battery-powered for uninterrupted safety First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack **Brand:** first alert **Price:** € 45.02 **Availability:** ✅ In Stock ## Summary > 🏠 Stay one step ahead—because your family deserves the safest home. ## Quick Answers - **What is this?** First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack by first alert - **How much does it cost?** € 45.02 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.hr](https://www.desertcart.hr/products/2536037-first-alert-co400-carbon-monoxide-co-detector-battery-operated-alarm) ## Best For - first alert enthusiasts ## Why This Product - Trusted first alert brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - • **Loud & Clear Alerts:** An 85-decibel alarm cuts through noise to instantly warn you and your family of danger. - • **Precision Protection:** Equipped with a cutting-edge electrochemical sensor that accurately detects invisible, odorless carbon monoxide threats. - • **Smart Safety Signals:** Visual and audible low battery alerts plus end-of-life chirp keep you ahead of maintenance for continuous protection. - • **Unplugged Peace of Mind:** Battery-operated design means no outlet needed—place it anywhere in your home for ultimate flexibility. - • **Effortless Setup & Trust:** No installation hassle with optional wall mount; backed by a 5-year limited warranty and UL certification for trusted reliability. ## Overview The First Alert CO400 is a battery-powered carbon monoxide detector featuring an advanced electrochemical sensor for accurate detection of CO levels. It emits a loud 85dB alarm to alert occupants of danger, operates on a replaceable 9V battery ensuring functionality during power outages, and includes smart alerts for low battery and end-of-life. Easy to install with no wiring required, it comes with a 5-year limited warranty and meets UL safety standards, making it a reliable choice for comprehensive home safety. ## Description Product Description The First Alert CO400 carbon monoxide alarm uses an electrochemical sensor the most accurate technology available. The permanent sensor lasts up to 5 years. It is powered by a 9V replaceable battery giving you peace of mind even during power outages. The test/silence button silences the alarm and allows you to test its functionality. The unit monitors and re alarms if carbon monoxide level persist sounding a loud 85 decibel horn. No installation is required and the attractive design allows the unit to be placed anywhere you need it. It includes an optional wall mount with no outlet required. An audible and visual battery signal alerts you to replace the battery. Pull down action chart has convenient guide on what to do if an alarm sounds. 5 year limited warranty. Ul listed. desertcart.com Carbon monoxide (CO) is the leading cause of accidental poisoning deaths in America, yet many people don't know they are suffering from CO poisoning until its too late. Since symptoms of CO poisoning are like the flu, you might not even know you're in danger at first. That's why a carbon monoxide alarm is an excellent way to protect your family. It can detect the CO you can't see, smell or taste in the air. The First Alert CO400 carbon monoxide alarm uses an electrochemical carbon monoxide sensor-the most accurate technology available. The permanent sensor lasts up to five years. It is powered by on 9V replaceable battery giving you peace of mind even during power outages. The test/silence button both silences the alarm and allows you to test its functionality. The unit monitors and re-alarms if carbon monoxide levels persist sounding a loud 85-decibel horn. No installation is required and the attractive design allows the unit to be placed anywhere you need it. It includes an optional wall mount with no outlet required. An audible and visual low battery signal alerts you to replace the battery. Pull down action chart has convenient guide on what to do if an alarm sounds. 5 year limited warranty. UL listed. --Bree Norlander Manufacturer Contact Information 1 (800) 323-9005. Review: Great Carbon Monoxide Detector – Easy to Install and Reliable! - I bought two of the First Alert Carbon Monoxide Detectors (model CO400), and I’m very happy with them. They were super easy to install — no outlet needed since they run on batteries. I just mounted them on the wall, and they were ready to go in minutes.I like that the battery operation means I can place them anywhere in my home without worrying about finding a plug. The alarm is loud enough to hear clearly, and the design is compact and simple.It gives me peace of mind knowing my family is protected. Overall, great value, easy setup, and reliable safety product. Highly recommend! Review: for home, for travel, for car (add to winter car bag in case stuck in blizzard). 9 volt included - I purchased two packs of the pack of 2. So far so good!? Tested fine. Hope it actually works, which is why I went with a name brand. This is not the place to skimp. The C0400 carbon monoxide detector comes with a 9 volt battery. I knew I needed to replace my existing detector (they dont last forever, and need to be replaced ever so often) and I did not want the plug in style. I wanted battery operated so I could place it wherever I wanted and not be limited to available outlets. I also bought a second pack as a gift. I prefer giving practical, functional gifts, especially stuff that people tend to not want to buy, such as smoke alarms, fire extinguishers, carbon monoxide detectors. If you travel, consider a battery operated detector such as this. Dont trust that a hotel room has you covered, or someone else's house. It is small and light weight enough that it should be the thing to pack (take out battery, store separately until in room). I will likely buy an additional pack. Right now I have one on the first floor, and one outside my second floor bedroom door. I think having one in the basement and another in actual bedroom or elsewhere (spread out) would be better. Watch for sales, but if need be just buy them at any cost so you have them. I am even thinking about adding one to my winter car kit. If ever stuck in a blizzard and had to stay in my car for any length of time, having a detector will help as CO2 levels can quickly rise if running car (or if a few people are simply breathing without the window open a crack) to keep warm. Tail pipes can easily clog especially if windy. So yeh, simple thing to stay safe and alive ## Features - Keep your family safe with this easy to use, battery operated carbon monoxide alarm; Battery powered alarms provide continuous monitoring of CO levels, even if there's a power failure - Features an advanced electrochemical carbon monoxide sensor that accurately detects carbon monoxide levels, no matter where the detector is placed in the room.The alarm sequence should last 5-6 seconds. If it does not alarm, make sure fresh batteries are correctly installed, and test it again. If the unit still does not alarm, replace it immediately - A loud 85 decibel alarm sounds when CO levels reach dangerous , Battery Replaceable - Yes - To ensure complete protection make sure to place one on each level of your home and in each bedroom - 5-year limited warranty; Equipped with end of life signal chirp, so you know when it’s time to replace the unit for safety - All first alert CO alarms are rigorously tested to meet UL standards - First Alert has been the most trusted brand in home safety since launching the first residential smoke alarm in 1958 (Based on a First Alert Brand Trust Survey in February 2018) ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B000N8OYXI | | Alarm | Audible | | Best Sellers Rank | #225 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #3 in Carbon Monoxide Detectors | | Brand | First Alert | | Built-In Media | Alarm; Mounting Bracket; User Manual; 9V Battery | | Color | White | | Customer Reviews | 4.6 out of 5 stars 22,869 Reviews | | Enclosure Material | Multi | | Global Trade Identification Number | 00029054000699 | | Item Dimensions D x W x H | 1"D x 5"W x 3"H | | Item Type Name | First Alert CO400FF Battery Powered Carbon Monoxide Alarm | | Item Weight | 7.2 ounces | | Manufacturer | First Alert | | Manufacturer Contact Information | 1 (800) 323-9005. | | Manufacturer Warranty Description | 5 Year Limited Warranty | | Mfr Part Number | CO400 | | Model Number | CO400 | | Number of Items | 1 | | Operating Humidity | 10-95% RH | | Power Source | Battery Powered | | Product Dimensions | 1"D x 5"W x 3"H | | Product Style | Battery Powered | | Sensor Type | Electrochemical | | Style | Battery Powered | | UPC | 029054000699 | | Unit Count | 1.0 Count | ## Product Details - **Alarm:** Audible - **Brand:** First Alert - **Color:** White - **Global Trade Identification Number:** 00029054000699 - **Item Weight:** 7.2 ounces - **Operating Humidity:** 10-95% RH - **Power Source:** Battery Powered - **Product Dimensions:** 1"D x 5"W x 3"H - **Sensor Type:** Electrochemical - **Style:** Battery Powered ## Images ![First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack - Image 1](https://m.media-amazon.com/images/I/51RBX7hitxL.jpg) ![First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack - Image 2](https://m.media-amazon.com/images/I/71hAwlBG2vL.jpg) ![First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack - Image 3](https://m.media-amazon.com/images/I/61iNBAMSOZL.jpg) ![First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack - Image 4](https://m.media-amazon.com/images/I/61JZgbyiECL.jpg) ![First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack - Image 5](https://m.media-amazon.com/images/I/61gHs4yM9gL.jpg) ## Available Options This product comes in different **Pattern, Size** options. ## Questions & Answers **Q: Has anyone else received the CO400 with one 9 volt battery instead of the two AA batteries listed in description and on picture of packaging display?** A: Yes, Received the 9-Volt battery version. I live in California. I'm not a lawyer but my research shows that in California Smoke detectors and Combo Smoke/Carbon detectors must come with a 10 year lifespan battery. This law does not seem to apply to devices that only detect Carbon Monoxide like that one for sale here. **Q: Why can't this be purchased in or shipped to California?** A: I live in California. Yes, I received the 9-Volt battery version. I'm not a lawyer but my research shows that in California Smoke detectors and Combo Smoke/Carbon detectors must come with a 10 year lifespan battery. This law does not seem to apply to devices that only detect Carbon Monoxide like that one for sale here. **Q: the package picture shows 9-volt, but sounds like it is a crapshoot on what they will send you. which is better and lasts longer, 2AA or 1 9V? I hate taking out and putting in 9v batteries. so many to choose from. would prefer plug-in but would be too low.** A: I bought a package of AA batteries because this item description said it takes 2 AA. It does not. It takes (and comes with) one 9V. This is model CO400. **Q: Red light is on. Is that normal? Tested and it chirps with test. Also checked battery.** A: YEs, red light is normal. If red light blinks - read manufacturer's guide in link below. https://www.brkelectronics.com/pdfs/2017/10/23/803bf30c.pdf ## Customer Reviews ### ⭐⭐⭐⭐⭐ Great Carbon Monoxide Detector – Easy to Install and Reliable! *by J***N on November 12, 2025* I bought two of the First Alert Carbon Monoxide Detectors (model CO400), and I’m very happy with them. They were super easy to install — no outlet needed since they run on batteries. I just mounted them on the wall, and they were ready to go in minutes.I like that the battery operation means I can place them anywhere in my home without worrying about finding a plug. The alarm is loud enough to hear clearly, and the design is compact and simple.It gives me peace of mind knowing my family is protected. Overall, great value, easy setup, and reliable safety product. Highly recommend! ### ⭐⭐⭐⭐⭐ for home, for travel, for car (add to winter car bag in case stuck in blizzard). 9 volt included *by P***Y on January 13, 2023* I purchased two packs of the pack of 2. So far so good!? Tested fine. Hope it actually works, which is why I went with a name brand. This is not the place to skimp. The C0400 carbon monoxide detector comes with a 9 volt battery. I knew I needed to replace my existing detector (they dont last forever, and need to be replaced ever so often) and I did not want the plug in style. I wanted battery operated so I could place it wherever I wanted and not be limited to available outlets. I also bought a second pack as a gift. I prefer giving practical, functional gifts, especially stuff that people tend to not want to buy, such as smoke alarms, fire extinguishers, carbon monoxide detectors. If you travel, consider a battery operated detector such as this. Dont trust that a hotel room has you covered, or someone else's house. It is small and light weight enough that it should be the thing to pack (take out battery, store separately until in room). I will likely buy an additional pack. Right now I have one on the first floor, and one outside my second floor bedroom door. I think having one in the basement and another in actual bedroom or elsewhere (spread out) would be better. Watch for sales, but if need be just buy them at any cost so you have them. I am even thinking about adding one to my winter car kit. If ever stuck in a blizzard and had to stay in my car for any length of time, having a detector will help as CO2 levels can quickly rise if running car (or if a few people are simply breathing without the window open a crack) to keep warm. Tail pipes can easily clog especially if windy. So yeh, simple thing to stay safe and alive ### ⭐⭐⭐⭐⭐ Works as advertised reasonable price. *by R***N on April 28, 2026* Great product lots of instructions easy to install ## Frequently Bought Together - First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack - First Alert CO605 Plug-In Carbon Monoxide Detector with Battery Backup , White - Kidde Carbon Monoxide Detector, Battery Powered CO Alarm with LEDs, Test-Reset Button, Low Battery Indicator, Portable --- ## Why Shop on Desertcart? - 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016 - 🌍 **Shop Globally** — Access 737+ million products across 21 categories - 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price - 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members) - 🔒 **Secure Payments** — Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.hr/products/2536037-first-alert-co400-carbon-monoxide-co-detector-battery-operated-alarm](https://www.desertcart.hr/products/2536037-first-alert-co400-carbon-monoxide-co-detector-battery-operated-alarm) --- *Product available on Desertcart Croatia* *Store origin: HR* *Last updated: 2026-05-18*