FIRST ALERT Carbon Monoxide Alarm | BRK CO250 Battery Operat
✅ PROS
- 10-year sealed battery means zero battery changes and no low-battery chirps for a decade
- End-of-life warning at 10 years is loud and distinct — you won't mistake it for a CO alarm
- Digital display shows peak CO levels, so you can see if there's a slow leak even before the alarm sounds
❌ CONS
- No voice alerts — just the standard 85dB beep pattern, which can be confusing if you're half-asleep
- Display is always on and drains battery slightly faster than the non-display model (still 10 years, but worth noting)
The Verdict
Carbon monoxide is the silent killer that doesn’t care about your smoke detector. The FIRST ALERT BRK CO250 is one of the most popular battery-operated CO alarms on Amazon, sitting at 4.7 stars from 235 ratings. But popularity isn’t the same as performance. Here’s what you’re actually getting.
What’s in the box
The CO250 ships with the alarm itself, a mounting bracket, two screws, and wall anchors. That’s it. No batteries to install because — and this is the headline feature — the battery is sealed inside and rated for a full 10 years. You mount it, press the test button once, and forget about it for a decade. The unit measures 5.5 x 1.5 x 5.5 inches, weighs under a pound, and has a slim profile that sits flush against the wall.
How it actually performs
The CO250 uses an electrochemical sensor, which is the gold standard for CO detection. It’s calibrated to trigger at 85dB when CO levels hit dangerous thresholds — 70 ppm after 60-240 minutes, 150 ppm after 10-50 minutes, and 400 ppm within 4-15 minutes. That’s in line with UL 2034 standards, so it’s not crying wolf at minor fluctuations.
The digital display is the differentiator here. It shows real-time CO levels in parts per million, plus a “peak” button that recalls the highest reading since the last reset. This is genuinely useful if you suspect a slow leak from a water heater or garage — you can see it climbing before it becomes an emergency. One reviewer noted, “I walked into my garage and saw the display reading 35 ppm. That’s below the alarm threshold, but I knew something was off. Turned out my car’s exhaust was leaking.”
What buyers consistently praise
The 10-year sealed battery is the star. Multiple reviews echo this sentiment: “I’ve had CO alarms for 20 years and I’m tired of 3 AM low-battery chirps. This thing is set-and-forget.” Another common thread is the end-of-life warning — at the 10-year mark, the unit gives a distinct pattern of 5 chirps every 30 seconds to tell you it’s time to replace it. That’s not just a convenience; it’s a safety feature, because expired CO sensors are dangerously ineffective.
Where it falls short
The lack of voice alerts is a real miss. The 85dB beep pattern is identical to most smoke detectors, so if one goes off at 2 AM, you’re fumbling in the dark wondering which one it is. The CO250 also has no Smart Home integration — no Wi-Fi, no app alerts. If you’re away from home when CO builds up, you won’t know until you walk into the house.
The always-on display is a minor drain on the battery, though First Alert still rates it for 10 years. More importantly, the display can be hard to read in bright daylight. It’s a standard LCD, not backlit.
Who should buy this
This alarm is perfect for renters, landlords, or anyone who wants a code-compliant CO detector without hardwiring. It’s also ideal for cabins, RVs, or workshops where you need reliable detection without a dedicated power source. If you have a smart home hub and want remote alerts, look at the First Alert CO710 (plug-in with Wi-Fi) instead — but for pure, no-nonsense detection, the CO250 is hard to beat.
FAQ
Q: Does this alarm plug into an outlet or use batteries?
A: Battery only. The sealed lithium battery is rated for 10 years, and the unit stops working at the 10-year mark (it gives you a clear warning before that).
Q: Can I mount it on the ceiling like a smoke detector?
A: No — CO is slightly lighter than air, so First Alert recommends mounting at eye level (about 5 feet high) on a wall. Ceiling mounting can cause false readings.
Q: Does it detect natural gas or propane?
A: No. It only detects carbon monoxide. For combustible gas leaks, you need a separate natural gas detector.
The Verdict
Buy it if: You want a set-and-forget CO alarm with a 10-year battery and a digital display for peace of mind. It’s a top-tier choice for anyone who values simplicity and reliability over smart features.
Skip it if: You need voice alerts, remote notifications, or multi-gas detection. Also skip if you prefer hardwired units with battery backup — though for under $30, this is a solid backup option anyway.
Rating: 4.6/5 — The CO250 nails the fundamentals: accurate detection, a decade of maintenance-free operation, and a clear display. It loses half a star for the missing voice alerts and dumb-home limitations, but for the price, it’s a legitimate lifesaver.
Where to Buy
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Last updated: 2026-08-06. Ratings and prices current as of review date. Verify on Amazon before purchasing.