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First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack

4.7 4.7 out of 5 stars 19,440 ratings
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List Price: $41.99

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Purchase options and add-ons

Brand FIRST ALERT
Style Battery Powered
Power Source Battery Powered
Color White
Product Dimensions 1"D x 5"W x 3"H
Item Weight 7.2 ounces
Alarm Audible
Sensor Type Electrochemical
Material Multi

About this item

  • 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)
› See more product details

Customer ratings by feature

Easy to read
4.5 4.5
Easy to install
4.5 4.5
Accuracy
4.4 4.4
Value for money
4.3 4.3
See all reviews
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From the manufacturer

First Alert
What is carbon monoxide?

Common sources of Carbon Monoxide

Furniture

Dryer Vent

Chimney

What does the beep mean?

4 beeps and a pause

1 beep every minute

5 beeps every minute

Emergency: Carbon monoxide has been detected. Move to fresh air and call 911.

Low battery: It's time to replace the batteries in your carbon monoxide alarm.

End of life: It's time to replace your carbon monoxide alarm.

Recommended alarm placement

Looking for specific info?

Product guides and documents

User Manual (PDF)

Product 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.

Amazon.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

WARNING:

CHOKING HAZARD -- Small parts. Not for children under 3 yrs.

Top Brand: FIRST ALERT

Highly Rated
100K+ customers rate items from this brand highly
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First Alert CO400 Carbon Monoxide (CO) Detector, Battery Operated Alarm, 1-Pack
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Price-48% $21.99
List: $41.99		$20.99$26.99$27.99$12.99$18.99
Delivery
Get it as soon as Saturday, May 11
Get it as soon as Saturday, May 11
Get it as soon as Saturday, May 11
Get it as soon as Saturday, May 11
Get it as soon as Saturday, May 11
Get it as soon as Saturday, May 11
Customer Ratings
4.74.7 out of 5 stars19,440
4.64.6 out of 5 stars772
4.64.6 out of 5 stars379
4.74.7 out of 5 stars318
4.74.7 out of 5 stars3
4.64.6 out of 5 stars772
Easy to read
4.5
4.7
4.7
4.7
—
4.7
Easy to install
4.5
4.5
4.6
4.8
—
4.5
Accuracy
4.4
4.1
4.6
—
—
4.1
Value for money
4.3
4.1
—
5.0
—
4.1
Easy to use
4.2
—
4.7
4.8
—
—
Sold By
Amazon.com
Ecoey-direct
SITERWELL
Siterlink
Zhongminwenhua
Ecoey-direct
power source
Battery Powered
Battery Powered
Battery Powered
Battery Powered
Battery Powered
Battery Powered
sensor type
Electrochemical
Electrochemical
Electrochemical
Electrochemical
Electrochemical
Electrochemical
upper temperature rate
—
50 degrees celsius
—
—
40 degrees celsius
50 degrees celsius
style
Battery Powered
modern
Safety
—
—
Carbon Monoxide Alarm
alarm
Audible
Audible
Audible
Audible
Audible
Audible

Important information

Bulb Voltage

120 volts

Customer reviews

4.7 out of 5 stars
4.7 out of 5
19,440 global ratings

Customers say

Customers like the portability, ease of installation, performance, and value of the gas smoke fire alarm. For example, they mention it's compact, easy to place in smaller areas, and easy to pack into a suitcase. That said, opinions are mixed on quality and battery life.

AI-generated from the text of customer reviews

551 customers mention483 positive68 negative

Customers like the performance of the gas smoke fire alarm. They say it works great, is easy to set up and install, and the test function works correctly. Some say it's adequate, effective, and quiet. Overall, most are happy with the quality and price of the product.

"...And it seems to work fine when testing it." Read more

"Great product" Read more

"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...." Read more

"Item works great, easy to install and feel much safer." Read more

541 customers mention481 positive60 negative

Customers like the ease of installation of the gas smoke fire alarm. They mention that it comes with batteries, easy to understand instructions, and is small and discreet. Some like the small discreet size.

"There has not been any problems installing it. And it seems to work fine when testing it." Read more

"The products arrived in good condition and was easily activated and installed." Read more

"This product is a carbon monoxide detector. Easy install. Although the battery door was a bit difficult to open." Read more

"...They are easy to install and came with batteries." Read more

429 customers mention386 positive43 negative

Customers like the value of the gas smoke fire alarm. They say it's a good buy and priceless for peace of mind.

"Trust the brand name and quality. The price was excellent" Read more

"...This detector is great for what it is and I'm grateful that it's so affordable, so more people can access this type of device...." Read more

"I feel much safer in my home with these products. Worth the money." Read more

"Good brand and quality and price was good ! Good protection for the house." Read more

121 customers mention104 positive17 negative

Customers like the portability of the gas smoke fire alarm. They say it's compact, simple to operate, and easy to place in smaller areas. Some mention it'll lend a bit of peace of mind to travelers. They also say it fits perfectly into mount and is light weight enough that it should be the thing to take on travel.

"Lightweight and small. Bought to take with me while traveling as I don’t trust all hotels when it comes to carbon monoxide leaks." Read more

"Like that it is portable and easy to place in smaller areas." Read more

"Compact and easy to install" Read more

"Replacement fit the mounting of previous unit. Fit perfect. Previous unit lasted almost 10 full years." Read more

376 customers mention214 positive162 negative

Customers are mixed about the quality of the gas smoke fire alarm. Some mention it's well made and reassuring to have a reliable device that alerts them to potential carbon monoxide presence. Others say that it started beeping and at first they thought it was the batteries.

"The products arrived in good condition and was easily activated and installed." Read more

"When I opened the package and tried to test my alarm, there was no light & no response...." Read more

"This product is a carbon monoxide detector. Easy install. Although the battery door was a bit difficult to open." Read more

"...the UL timelines, and even if there's an unsafe CO level, the device might not alarm if I turn my car off a half hour early...." Read more

268 customers mention108 positive160 negative

Customers have mixed opinions about the battery life of the gas smoke fire alarm. Some mention that it comes with batteries, while others say that it arrived with dead batteries.

"...Turns out the battery it came with was dead." Read more

"...They are easy to install and came with batteries." Read more

"...there's no way for you to access that info, and the alarm is unreliable for intermittent leaks...." Read more

"This product looks to be great nice it came with batteries." Read more

Batteries Weren't Dead - Testing Instructions Weren't Clear Enough
4 Stars
Batteries Weren't Dead - Testing Instructions Weren't Clear Enough
When I opened the package and tried to test my alarm, there was no light & no response. I thought the batteries were dead so I bought new ones, which did the same thing.It tuns out that testing requires holding the Test button, not tapping it. The light flashes once a minute, so 99% of the time, the unit appears to be dead.Once I knew to hold the button, I was able to confirm they appear to be operating properly after all. Better labelling would have saved me the cost of replacement batteries.
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Top reviews from the United States

LA
5.0 out of 5 stars Seems to work fine.
Reviewed in the United States on April 23, 2024
Size: Pack of 1Pattern Name: DetectorVerified Purchase
There has not been any problems installing it. And it seems to work fine when testing it.
Helpful
 Report
LDHarris
5.0 out of 5 stars As advertised ! Good value.
Reviewed in the United States on April 19, 2024
Size: 2 Count (Pack of 1)Pattern Name: DetectorVerified Purchase
The products arrived in good condition and was easily activated and installed.
Helpful
 Report
Grantorino
5.0 out of 5 stars Arrived fast and easy to install
Reviewed in the United States on April 21, 2024
Size: Pack of 1Pattern Name: DetectorVerified Purchase
Great product
Helpful
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Skent
4.0 out of 5 stars Great price
Reviewed in the United States on March 2, 2024
Size: 2 Count (Pack of 1)Pattern Name: DetectorVerified Purchase
Lightweight and small. Bought to take with me while traveling as I don’t trust all hotels when it comes to carbon monoxide leaks.
One person found this helpful
Helpful
 Report
terrie
5.0 out of 5 stars Very easy install for carbon monoxide alert
Reviewed in the United States on April 21, 2024
Size: Pack of 1Pattern Name: DetectorVerified Purchase
This product is a carbon monoxide detector. Easy install. Although the battery door was a bit difficult to open.
One person found this helpful
Helpful
 Report
Jamie C.
5.0 out of 5 stars Must Have
Reviewed in the United States on April 15, 2024
Size: 2 Count (Pack of 1)Pattern Name: DetectorVerified Purchase
These are great and can save you and your loved ones lives. They are easy to install and came with batteries.
Helpful
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Skippy
5.0 out of 5 stars Works great in different areas .
Reviewed in the United States on April 28, 2024
Size: 2 Count (Pack of 1)Pattern Name: DetectorVerified Purchase
Like that it is portable and easy to place in smaller areas.
Helpful
 Report
Timothy
5.0 out of 5 stars products are high quality.
Reviewed in the United States on April 6, 2024
Size: Pack of 1Pattern Name: DetectorVerified Purchase
Stay safe with this easy-to-install, 9-volt battery-powered carbon monoxide alarm; provides continuous monitoring of CO levels, even if your power fails
Helpful
 Report

Top reviews from other countries

Monica Ileana Silva Davila
5.0 out of 5 stars Bien!
Reviewed in Mexico on March 18, 2024
Size: 2 Count (Pack of 1)Pattern Name: DetectorVerified Purchase
Excelente producto
Report
Amazon Customer
5.0 out of 5 stars Excellent and easy to install
Reviewed in Canada on December 17, 2016
Size: Pack of 1Pattern Name: DetectorVerified Purchase
I purchased this alarm to install in the upstairs hallway between bedrooms. It was very easy to install and works perfectly and provides the added security I required. I was surprised and happy at how quickly the parcel arrived!
Report
Corey S
5.0 out of 5 stars Simple
Reviewed in Canada on August 18, 2018
Size: Pack of 1Pattern Name: DetectorVerified Purchase
Straight forward, and easy to install. Affordable too, everyone should have one.
Report
roger skinner
5.0 out of 5 stars Safety
Reviewed in Canada on March 18, 2019
Size: Pack of 1Pattern Name: DetectorVerified Purchase
This unit is very similar to the one we had for over 15 years. CO2 is a danger & we now feel safe again with the new alarm in place. The unit is just a simple plug in, but we did have to read up on where to put it. Placing it correctly is important so study up & get it right.
Report
Chuck
5.0 out of 5 stars Seems good
Reviewed in Canada on November 7, 2017
Size: Pack of 1Pattern Name: DetectorVerified Purchase
Quickly mounted to the wall and put batteries in. Tested. Made beep noises that split eardrums. Due to the battery nature of it it can mount anywhere close to the ground to detect CO quickly.

I wont truly know if it works, and I hope I never need to, but appears solid.
Report