First Alert CO400 Battery Carbon Monoxide Alarm
- Battery powered, electrochemical sensor
- Audible and visual alarm
- 4 x 9 x 6 inches, 12.8 ounces
- 5-year warranty
- White
Last refreshed Sep 8, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A battery unit that warns with both a horn and a light. The listing is unclear whether the pack holds one or two.
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ASIN: B002GP7CZSModel: CO400Category: Carbon Monoxide Detectors
Overview
Not a plug-in alarm, this First Alert runs on batteries and can sit anywhere in the home. It uses an electrochemical sensor and warns with an audible alarm and a visual signal.
Battery power means placement is not tied to an outlet, and the alarm works in an outage. The battery type is not listed. The count of alarms per pack is inconsistent.
Who it's for
A household placing alarms outside sleeping areas gets a flexible battery unit. Those wanting a readout of current levels should buy a model with a display.
Pros and cons
- Battery power, no outlet needed
- Audible and visual alarm
- Five year warranty
- Battery type not listed
- Pack count unclear
- No digital display
- Enclosure material listed oddly
Performance notes
An electrochemical sensor reacts to carbon monoxide in the air, and the alarm sounds when levels stay high. Battery power makes it independent of outlets. Placement near sleeping areas affects how well it protects.
Where it stands among carbon monoxide detectors
- #3 most-searched brand and model of the 17 carbon monoxide detectors lines we track (by search demand, not sales).
From the specs of the 30 carbon monoxide detectors we list; not a test result.
Specifications
| Brand | First Alert |
|---|---|
| Model | CO400 |
| Dimensions & fit | |
| Item Dimensions D X W X H | 4 x 9 x 6 inches |
| Item weight | 12.8 ounces |
| Power & efficiency | |
| Power Source | Battery powered |
| Construction & materials | |
| Color | White |
| Included components | |
| Unit Count | 2 |
| Warranty & support | |
| Manufacturer Warranty Description | 5-year |
| Other details | |
| Sensor Type | Electrochemical |
| Alarm | Audible, visual |
| BuiltIn Media | Carbon Monoxide (CO) Detector |
| Item Highlight | CO400 |
| Operating Humidity | 10-95% RH |
Frequently asked questions
How many alarms are in the First Alert CO400 pack?
The listing shows a unit count of 2 but a number of items of 1, so confirm the pack size with the seller.
Does the First Alert CO400 plug in?
No. It is battery powered.