First Alert CO400 Battery Carbon Monoxide Alarm
- Power Source: Battery
- Sensor Type: Electrochemical
- Alarm: Audible, Visual
- Operating Humidity: 10-95% RH
Last refreshed Sep 8, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A straightforward 2-pack battery alarm for multi-room coverage, without the display or peak-level memory that First Alert's CO615 and CO710 add.
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ASIN: B002GP7CZSModel: CO400Category: Carbon Monoxide Detectors
Overview
A 2-pack of battery-powered carbon monoxide alarms from First Alert, model CO400, built for covering more than one floor or bedroom without a digital display.
Running on batteries rather than a wall outlet, the CO400 goes anywhere a detector is needed and keeps monitoring through a power failure by default rather than as a backup mode. First Alert sells it as a pair specifically so one can go on each floor or in each bedroom, the placement it recommends for complete coverage. There is no digital readout here, so the interface is limited to the alarm itself and the end-of-life chirp.
- 2-pack
- Battery operated
- End-of-life chirp
- UL tested
Who it's for
Buyers covering multiple rooms or floors who want two simple, battery-only alarms rather than paying for a digital display on each. Not the pick for someone who specifically wants a peak-level number.
Pros and cons
- Sold as a 2-pack for multi-room coverage
- Battery powered, no outlet needed
- 85 decibel alarm
- No digital display or peak-level readout
- 5-year warranty, shorter than First Alert's 10-year models
Performance notes
The electrochemical sensor is rated to read CO levels accurately regardless of where in the room the unit sits, which is what lets it work as a tabletop or wall unit without positioning rules. Running entirely on battery means there is no outlet dependency, but it also means the 5-year limited warranty and the end-of-life chirp are the only signals for when to replace it.
Specifications
| Brand | First Alert |
|---|---|
| Model | CO400 |
| Dimensions & fit | |
| Item Weight | 0.8 pounds |
| Item Dimensions D X W X H | 4 × 9 × 6 inches |
| Power & efficiency | |
| Power Source | Battery |
| Construction & materials | |
| Enclosure Material | Carbon |
| Color | White |
| Included components | |
| Unit Count | 2 |
| Warranty & support | |
| Manufacturer Warranty Description | 5-Year |
| Other details | |
| Sensor Type | Electrochemical |
| Alarm | Audible, Visual |
| Operating Humidity | 10-95% RH |
| Number Of Items | 1 |
| Product Style | Battery Powered |
| Mfr Part Number | co400cn2 |
| Builtin Media | Carbon Monoxide (CO) Detector |
| Item Type Name | Carbon Monoxide (CO) Detector |
| Item Highlight | CO400 |
Frequently asked questions
Does the First Alert CO400 come as a single unit or a pack?
It is sold as a 2-pack, positioned for placing one alarm on each floor and in each bedroom.
Does the First Alert CO400 have a digital display?
No. It is an alarm-only unit with an end-of-life chirp, unlike First Alert's CO615 and CO710, which add a digital screen.
How long is the First Alert CO400 covered under warranty?
It carries a 5-year limited warranty.