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?

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.

Why can't this be purchased in or shipped to California?

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.

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.

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.

Red light is on. Is that normal? Tested and it chirps with test. Also checked battery.

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

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First Alert Battery Carbon Monoxide Alarm | CO400

Product ID: 2536037

Details

Alarm
Audible
Brand
First Alert
Color
White
Global Trade Identification Number
Item Weight
7.2 ounces
Operating Humidity
10-95% RH

📡Electrochemical sensor - ultra accurate CO detection

🔊85 dB alarm - loud & clear alert

🔋9V replaceable battery - power backup

$48.97

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Description

🚨 Stay ahead of invisible danger with First Alert’s smartest CO detector yet!

INSTANT ALERTS - Loud 85-decibel alarm guarantees you’ll hear danger before it’s too late.
EFFORTLESS SETUP - No installation needed—place it anywhere or use the optional wall mount for flexible protection.
SMART MAINTENANCE - End-of-life signal and low battery alerts keep your home safety system always ready.
PRECISION DETECTION - Advanced electrochemical sensor delivers the most accurate carbon monoxide readings available.
UNINTERRUPTED SAFETY - Battery-powered design ensures continuous CO monitoring even during power outages.

The First Alert CO400 is a battery-operated carbon monoxide detector featuring a highly accurate electrochemical sensor and a loud 85 dB alarm. It requires no installation, offers continuous monitoring even during power failures, and includes smart alerts for battery replacement and end-of-life. Backed by a 5-year limited warranty and UL certification, it’s a trusted, easy-to-use safety essential for every home.

Specifications

ASIN	B000N8OYXI
Alarm	Audible
Best Sellers Rank	#348 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #5 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 23,058 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	11.2 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 Count

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$48.97

Duties & taxes included

In stock

Sold byAmazon USADelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to USA.

Secure transaction

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TrustScore 4.5 | 7,300+ reviews

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The product quality is outstanding. Exactly what I needed for my work.

1 month ago

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Received my product in pristine condition. Great service overall.

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