10 Best Carbon Monoxide Detectors 2025 in the United States

The First Alert BRK SC9120B-3 is a reliable choice for anyone looking to protect their home from both smoke and carbon monoxide hazards. It uses two types of sensors: an electrochemical sensor for detecting carbon monoxide, and an ionization sensor that reacts quickly to fast-burning fires. This dual-sensor approach enhances safety by covering different types of fire and gas risks.

One of the standout features is its hardwired design combined with a battery backup. This means the alarms will keep working even during a power outage, giving you peace of mind around the clock. The unit’s alert system includes an 85-decibel siren—loud enough to wake most people—and indicator lights that clearly show what kind of danger is detected.

Installation is straightforward thanks to universal mounting brackets and a tamper-resistant design, making it suitable for use in various locations around the home. The detector can also be interconnected with other compatible First Alert alarms, so if one unit senses danger, all alarms will sound, improving safety. The display is simple, with indicator lights and a single test/silence button that makes it easy to check the system or temporarily quiet a false alarm. It also comes with a dust cover to help keep the sensor clean. This 3-pack is ideal for homeowners who want dependable, long-term monitoring of both smoke and carbon monoxide with backup power, especially in larger homes or multiple rooms. Note that installation requires wiring, which might need professional help if you’re not comfortable with electrical work.

The First Alert CO400 carbon monoxide detector is a solid choice for anyone wanting dependable CO monitoring without the hassle of wiring. It uses an advanced electrochemical sensor, which is known for accurately detecting dangerous CO levels. Since it's battery operated using included AA batteries, you can place it anywhere in your home, even where power outlets are scarce, and it will keep working during power outages. The alarm is loud enough (85 decibels) to alert you clearly if CO levels become unsafe. This model comes with a practical end-of-life signal to remind you when it’s time to replace the device, helping maintain safety without guesswork.

It’s designed for easy installation—just place it on any level of your home or inside bedrooms, as recommended. The compact, white design is unobtrusive and fits most home styles. Users appreciate its reliability and the 5-year limited warranty adds confidence in its durability. One thing to note is that it does not have a digital display to show current CO levels, which some users might miss if they want detailed real-time info. Also, since it is battery powered, you will need to occasionally replace batteries to keep it functional.

For a simple, effective, and portable carbon monoxide detector, this model covers the essential features that most families need to enhance their home safety.