Carbon monoxide, also called the “invisible killer,” doesn’t smell or taste and can poison you within minutes. It can seep from faulty stoves or furnaces and can be emitted by vehicles and portable generators operated indoors. Poisoning from carbon monoxide kills hundreds and injures tens of thousands every year. The best carbon monoxide detectors can help you protect yourself against this potentially deadly gas that you can’t see or smell.

Most of the portable carbon monoxide detector we tested use electrochemical sensors with electrodes submerged in an electrically conductive solution, called an electrolyte. Carbon monoxide entering the gas-permeable container causes a chemical reaction that changes the current passing through the electrolyte. The specific change in current tells the sensor what the concentration of carbon monoxide is. Other types of CO detectors use a gel that absorbs carbon monoxide, then turns a color and emits a light signal when the gel has absorbed enough to trigger a safety alarm.

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The SGT-P portable carbon monoxide detector is compact enough to slip into a travel bag, but still accurate and durable. It’s easy to read at a glance and shows real-time gas levels and peak CO readings over the previous 12 hours. It can even be attached to a car dashboard using 3M adhesive and is waterproof and dustproof.

Another solid choice is the plug-in Weshlgd model. It’s great for people who don’t want to keep track of battery levels or need a rechargeable option. This one has an at-a-glance digital display that shows air quality and is easy to read, and it comes with a long-life lithium battery.

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