Best plug-in in CO alarms
A plug-in CO alarm with a 9 V backup, so it keeps watching when the power fails and a generator or heater is running. US model (UL 2034); no Canadian listing stated.
Our score: 7.8/10 out of 10Researched, not lab-tested
- Detects
- Carbon monoxide
- Power
- Plug-in, battery backup
- US listing
- UL 2034
- Canadian listing
- None stated (US model)
Is it right for you?
Pros
- Conforms to UL 2034, the US CO alarm standard (First Alert's page)
- 9 V backup keeps it watching through a power outage
- 85 dB alarm at 10 ft; electrochemical sensor
- End-of-life warning; 7-year limited warranty
Cons
- US model: no Canadian (CSA 6.19) listing stated
- No display, so you can't see a low CO reading
- Goes only where there's an outlet, low on the wall
- Backup 9 V battery needs changing at least twice a year
- Best for
- US homes that want CO coverage outside bedrooms with nothing to install, and that run a generator, fuel heater or furnace through winter outages.
- Not for
- Canadian homes (choose an alarm with a Canadian certification mark), or anyone who wants a CO reading on a display.
Our verdict
Outages are when carbon monoxide risk rises: a generator in the yard, a fuel heater, a furnace working hard. A plug-in alarm that stops when the power stops would be no use then, and the CO3-P01 doesn’t: a replaceable 9 V battery keeps it watching when the outlet goes dead. First Alert lists it as conforming to UL 2034, the US standard for CO alarms, with an electrochemical sensor, an 85 dB alarm at 10 ft, an end-of-life warning and a seven-year limited warranty.
It is the simplest way to add CO coverage outside bedrooms in a US home: plug it in and it’s working. The catches are that it has no display, so you can’t see a low CO level building, it sits wherever there’s an outlet, and the backup battery needs changing. It is a US model, with no Canadian certification listed.
Setup and safety
If a CO alarm sounds, get everyone out at once, call 911 from outside and don’t go back in (Health Canada). An alarm doesn’t make an indoor generator safe: run generators outdoors only, at least 6 m (20 ft) from the house, exhaust pointed away from doors and windows (CPSC).
Where it goes. Health Canada says the most important place for a battery-backed CO alarm is the hallway outside the bedrooms, so it wakes people. CPSC asks for CO alarms on every level of the home and outside sleeping areas, interconnected where possible. A smoke alarm doesn’t detect CO, so you need both (Health Canada).
Keeping it working. First Alert says to test it regularly with the test button (CPSC suggests monthly), change the 9 V battery at least twice a year, and replace the alarm at least every seven years, when its end-of-life warning sounds. Fit the battery before relying on it: that battery is the only thing that keeps it working in an outage.
In Canada. Health Canada asks buyers to choose CO alarms with a Canadian certification mark on both the alarm and its packaging, and to confirm this with online sellers. This US model shows none. See the CO alarms we compare.
Specs
First Alert CO3-P01 Plug-In Carbon Monoxide Alarm with Battery Backup
Alarm
| Detects | Carbon monoxide |
|---|---|
| Power | Plug-in, battery backup |
| Backup battery | 1 × 9 V alkaline, replaceable |
| Sensor | Electrochemical |
| CO reading display | No |
| End-of-life warning | Yes |
Listing
| US listing | UL 2034 |
|---|---|
| Canadian listing | None stated (US model) |
Other details
| Alarm loudness | 85 dB |
|---|---|
| Warranty | 7 years |
Maker’s figures, checked 3 Nov 2026.
CO3-P01 questions
Does the CO3-P01 work during a power outage?
Yes, as long as its 9 V backup battery is fitted and fresh. It runs from the outlet normally and switches to the battery when the power fails, which is when generators and fuel heaters raise CO risk. First Alert says to change that battery at least twice a year.
Where should I plug it in?
In an outlet in the hallway outside the bedrooms first, which Health Canada calls the most important spot. For fuller coverage CPSC asks for a CO alarm on every level of the home. A plug-in can only go where there’s an outlet.
How long does it last?
First Alert says to replace it at least every seven years, and it gives an end-of-life warning when it is due. The limited warranty is also seven years.
