First Alert Carbon Monoxide Alarms & Detectors

Which first alert carbon monoxide alarm fits each room?

Short answer: the first alert carbon monoxide alarm line is nine models deep, and the split is power source plus display: battery basics (CO250, CO400), the digital-display CO410 with peak memory, three plug-ins, the voice-alert wireless-interconnect CO511, the 10-year sealed CO710 and the GCO1 CO-plus-explosive gas combo. Wider comparisons live in best carbon monoxide detectors and the category shelves for CO detectors and smart CO alarms.

Editor's pick — First Alert CO410
Digital ppm display with peak memory in a battery unit — the strongest currently-available all-rounder of the nine. Read the full listing.

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Three Decisions. Nine Models. One First Alert CO Alarm for Every Home.

UL 2034 | Electrochemical Sensor | 85 dB | Battery, Plug-In, and Combination Options

The First Alert CO710 is the best CO alarm in this collection for most households — a sealed 10-year lithium battery that never needs replacing, a digital display showing real-time PPM and room temperature, and a 10-year warranty that matches the alarm's full service life. If budget is the constraint, the CO606 delivers reliable plug-in CO protection with 9V battery backup for under —. Three decisions determine which of these nine models belongs in your home: power source (battery vs. plug-in), display and diagnostics (audible-only vs. real-time PPM readout), and special scenarios (multi-room interconnect, gas appliances, or rental properties). Each of the nine listings states UL 2034 listing; the CO600 note below concerns battery backup, not certification.

Quick Picks — All 9 First Alert CO Alarm Models at a Glance

All nine models: UL 2034 listed | Electrochemical CO sensor | 85 dB alarm. CO600 exception: AC-only, no battery backup — not recommended for residential use.

Decision 1 — Power Source: Battery or Plug-In?

The power source determines where you can install a CO alarm and whether it works during a power outage — the most critical reliability question for residential CO protection. Battery-powered alarms (CO710, CO410, CO511, CO400, CO250) can go anywhere — nightstand, shelf, hallway — with no outlet required, and they never fail during a power outage. Plug-in alarms with backup (CO615, CO606, GCO1) draw from AC power in normal conditions and switch to battery backup automatically when power fails — combining always-on reliability with outage protection. The CO600 is the one model to avoid for residential use: AC-only with no battery backup, it fails exactly when CO risk is highest — during outages when generators and space heaters run indoors.

Decision 2 — Display and Diagnostics: Do You Need to See CO Levels?

UL 2034 alarm thresholds are set for healthy adults — the standard does not require an alarm below 70 PPM at 1–4 hours or below 150 PPM at 10–50 minutes. CO at 30–50 PPM sustained for hours is dangerous for infants, elderly occupants, and people with cardiovascular or respiratory conditions. A digital display shows real-time PPM so you can act on rising CO before it reaches alarm thresholds. The CO710 displays PPM and room temperature; the CO615 and GCO1 display CO PPM. The CO410 adds peak memory — it records the highest CO level ever measured, even when you weren't home — making it the best diagnostic tool for homes with a history of CO events or aging gas appliances. Models without displays (CO606, CO400, CO511, CO250) provide code-compliant protection and sound when thresholds are crossed — appropriate for most secondary placements and budget-conscious primary coverage.

Decision 3 — Special Scenarios: Interconnect, Gas Appliances, or Rentals?

Three models in this collection address specific use cases that the standard battery or plug-in alarms do not cover:

• CO511 — Multi-story homes with a First Alert wireless network. The CO511 wirelessly interconnects with compatible First Alert smoke and CO alarms so that when any alarm detects CO, all connected alarms sound simultaneously. A voice alert announces the threat type — clearer than a beep in the middle of the night. If CO in the basement needs to wake someone on the third floor, the CO511 is the model to add to your First Alert wireless alarm system.
• GCO1 — Homes with gas ranges, furnaces, or propane appliances. The GCO1 adds combustible gas detection (natural gas, propane, methane) alongside CO detection in a single plug-in unit with 9V battery backup and digital CO display. Place it in the kitchen near a gas range, in a utility room near a gas furnace or water heater, or in a garage with gas-powered equipment. In rooms without gas appliances, a CO-only alarm is appropriate and more cost-effective.
• CO250 — Rental properties, dormitories, and managed facilities. The CO250 uses a locking tamper-resistant cover that prevents occupants from removing the battery to silence nuisance chirps. Property managers retain the key, maintaining alarm integrity between inspections. If you manage rental units or institutional housing with a CO alarm compliance obligation, the CO250 addresses a documented real-world problem that standard alarms do not.

CO600 Warning — Not for Residential Use: The CO600 is an AC-only plug-in alarm with no battery backup. It stops functioning during power outages — when generators, portable heaters, and gas stoves used for warmth create the highest residential CO risk. At a nearly identical price, the CO606 adds 9V battery backup. There is no reason to choose the CO600 for a residence. It belongs only in commercial or institutional settings with guaranteed building backup power.

Catalog honesty — availability and the fix this page just got

Four of the nine listings (CO250, CO511, CO615 and CO710) currently show as unavailable in the live catalog — including the 10-year CO710 this guide ranks highly — so treat those rows as reference until they restock, and lean on the in-stock CO400, CO410, CO600, CO606 and GCO1 meanwhile. A prior version of this page also mislinked seven of the nine models to the wrong product pages; every model link above now points to its own listing.

Our methodology

Model specs are quoted from each First Alert listing; UL 2034 behavior (alarm within 10–50 minutes at a sustained 150 ppm) is quoted from the standard. Residential guidance comes from NFPA home alarm guidance and CDC carbon monoxide basics. We do not test alarms and hold no safety certification.

Why trust this page

WC Safety is an independent review site with no products of its own; purchase links go to Amazon and earn an affiliate commission at no extra cost to you. No manufacturer pays for placement — which is why this page tells you its own top pick is currently unavailable and documents the link errors it corrected, instead of pretending neither happened.

Frequently Asked Questions — First Alert CO Alarms

Why does this first alert carbon monoxide alarm guide show no prices?

Because a third of the lineup is currently unavailable and stale prices mislead — the live listing carries the current number, one click away. Rankings here are about capability, not this week’s price.

Which in-stock First Alert model should I buy today?

The CO410’s digital ppm display with peak memory makes it the strongest available all-rounder; the CO400 covers no-outlet rooms on a 9-volt, and the GCO1 adds explosive-gas sensing for homes with gas appliances.

Which First Alert CO alarm is best for most homes?

The CO710 is the best overall choice for most households. Its sealed 10-year lithium battery eliminates annual replacements; the digital display shows real-time CO PPM and room temperature; and the 10-year warranty matches the alarm's full service life. It's freestanding — no mounting needed, renter-friendly. If zero battery maintenance and a display aren't priorities, the CO606 (plug-in + 9V backup) delivers code-compliant protection at the lowest plug-in cost.

How many CO alarms does my home need?

NFPA 720 requires a CO alarm on each level of the home (including basements) and within 10 feet of each sleeping area. A two-story, three-bedroom home typically needs a minimum of four alarms: one per bedroom and one per additional floor. Many states have adopted NFPA 720 or similar requirements into residential code; check your local building or fire code for the specific requirement in your jurisdiction. If you have an attached garage, a CO alarm near the interior garage door is advisable even if not code-required — CO from an idling vehicle can migrate into living spaces within minutes.

What is UL 2034 and why does it matter?

UL 2034 is the residential CO alarm standard published by Underwriters Laboratories. It defines the CO concentration levels and time durations at which an alarm must sound — for example, the alarm must activate at 70 PPM after 60–240 minutes, at 150 PPM after 10–50 minutes, and at 400 PPM within 4–15 minutes. Every model in this collection is UL 2034 listed. Most state residential CO alarm codes require UL 2034 listing; non-listed alarms do not meet code regardless of stated function. All nine First Alert models in this collection satisfy this requirement.

Is there a difference between a CO alarm and a CO detector?

In residential use, the terms are used interchangeably. All nine models in this collection are alarms — they detect CO and respond with an 85 dB audible signal when threshold levels are reached. In professional settings, "CO detector" sometimes refers to a monitoring device used for continuous measurement and data logging without a built-in audible alarm. For homes, any UL 2034 listed unit with an audible alarm meets the definition of a CO alarm under residential codes.

Where should I place a CO alarm — high or low on the wall?

Unlike smoke, CO is slightly lighter than air but distributes nearly evenly throughout a room — high-wall or ceiling mounting is not required. First Alert recommends placing CO alarms at least 5 feet from the floor to avoid interference from ground-level drafts. NFPA 720 permits placement at any height in a room. The most important placement rule is distance from sleeping areas: within 10 feet of each bedroom door. CO alarms should never be placed directly adjacent to fuel-burning appliances, inside bathrooms, or in areas of high humidity or extreme temperature.

How long do First Alert CO alarms last?

The electrochemical CO sensor in most First Alert residential alarms has a rated service life of 5–7 years. Warranty terms reflect this: the CO400 and GCO1 carry 5-year warranties; most other models in this collection carry 7-year warranties; the CO710 has a 10-year warranty matching its sealed battery life. When the end-of-life alarm activates, replace the unit — do not silence and continue using it. An aging electrochemical sensor may fail to detect CO reliably even though the audible circuitry continues to function.

What should I do when a CO alarm sounds?

If your CO alarm activates: (1) Do not ignore it or assume it is a false alarm. (2) Immediately move all occupants and pets outside to fresh air. (3) Call 911 or your local emergency number from outside. (4) Do not re-enter the building until emergency responders have investigated and cleared it. (5) If a CO source is identified (a running generator indoors, a malfunctioning furnace), do not operate it again until it has been inspected and repaired by a licensed professional. CO is colorless and odorless — there is no safe way to verify an alarm is false without proper equipment.

Can I use a First Alert CO alarm in an RV or boat?

Battery-powered First Alert CO alarms (CO710, CO410, CO400) can be used in RVs where they are placed in stable locations away from heat sources, cooking appliances, and high-vibration areas. They are not specifically certified for marine use. For boats and marine applications, look for CO alarms carrying UL 2034 plus UL 1524 marine listing. For RVs, some states and RV manufacturers specify alarm requirements — check applicable codes before installation.

Do I need both a smoke alarm and a CO alarm?

Yes — they are different sensors detecting different hazards. CO alarms detect colorless, odorless carbon monoxide gas from combustion sources. Smoke alarms detect particles from burning. A CO alarm will not detect smoke, and a smoke alarm will not detect CO. Both are required by residential codes in most states. Combination smoke/CO alarms exist, but the nine models in this First Alert CO-only collection are dedicated CO alarms optimized for CO detection — if you want combination units, see the combination alarm category.

What causes a CO alarm to chirp even when no CO is present?

A single chirp every 30–60 seconds is almost always a low-battery signal, not a CO alert. Replace the battery and the chirping should stop. A series of 4 chirps in a pattern (distinct from the continuous alarm tone) is the CO alarm — take this seriously and evacuate. A chirp pattern of 5 beeps every minute indicates the end-of-life signal — replace the entire unit. Never remove the battery to stop chirping without first identifying the chirp pattern: a low-battery chirp is a maintenance reminder, but the CO alarm and end-of-life chirp both require immediate action.

Researched and written by Steven Eaton, editor of WC Safety. Steven holds no safety certification and does not test products; this page compares what manufacturers publish, with the gaps in that record marked. Last reviewed July 2026.