10 Best Carbon Monoxide Detector 2025 in the United States

This NICGOL 4-in-1 carbon monoxide and natural gas detector stands out with its combined ability to monitor CO, natural gas leaks, temperature, and humidity, using catalytic sensors. It plugs into a standard AC outlet, avoiding the need for batteries, which makes it convenient for continuous use in homes, RVs, or similar spaces. The detector features both loud (≥85 dB) sound alarms and flashing red lights to quickly notify you of dangerous gas levels, which is especially useful in noisy environments or for those with hearing difficulties.

Its colorful LCD screen clearly displays real-time gas concentrations, temperature, and humidity, helping you stay informed about your environment. The included test button lets you easily check alarm functionality, which is important for safety confidence. It’s energy-efficient with low power consumption and compact enough not to clutter your space.

With very positive customer ratings and a reputable sensor type, this detector is a solid choice for those needing multi-gas detection in homes or mobile settings, though buyers looking for networked alarms or detailed warranty coverage may want to explore other options.

The First Alert Carbon Monoxide Detector CO400 is a reliable, battery-operated device designed to keep your home safe from dangerous carbon monoxide (CO) gas. It uses an electrochemical sensor, which is known for accurate CO detection and is considered one of the best types for this purpose. Because it runs on 4 included AA batteries, it doesn't need to be plugged in or hardwired, making it easy to place anywhere in your home—even during power outages. The alarm is loud at 85 decibels, which is strong enough to wake most people if CO levels become unsafe. It also provides both audible and visual alerts to catch your attention.

A helpful feature is the end-of-life signal that lets you know when it's time to replace the unit, which helps maintain safety without you needing to remember the date. The device comes with a 5-year limited warranty, which is standard for many CO detectors. However, this model does not offer interconnectivity, meaning if you have multiple units, they won’t alert you simultaneously when one detects CO. It also lacks some advanced features like a digital display showing current CO levels, which some users might find useful.

The compact size and no-installation design make it convenient for immediate use, but placing one on each floor and in bedrooms is recommended for full protection. This detector is a straightforward and trustworthy choice for anyone looking for easy-to-use, battery-powered CO monitoring without extra complexity.

The First Alert SMICO100-AC Combination Smoke and Carbon Monoxide Alarm is designed to provide reliable protection for your home. With its ionization sensor, it detects smoke and carbon monoxide effectively, offering dual protection. The hardwired unit comes with a battery backup, ensuring continuous operation during power outages, which is a significant advantage for safety.

Its interconnectivity feature ensures that if one alarm goes off, all alarms in the network will sound, providing comprehensive coverage throughout your home. The Quick Connect Plug feature makes installation straightforward without the need for extensive rewiring, which is convenient for most users. Additionally, the test/silence button allows for easy maintenance and ensures the alarm is functioning correctly.

It is worth noting that being a hardwired unit, it requires a bit more effort during initial setup compared to battery-only models. The ionization sensor is also more prone to nuisance alarms from cooking, although the advanced sensing technology aims to minimize this. If you’re looking for a robust, interconnected smoke and CO alarm with battery backup, this could be a solid choice.