Detectors measure CO levels over time and sound an alarm when harmful concentrations are detected. They help prevent carbon monoxide poisoning by giving people enough warning to safely ventilate the area or evacuate. Some system-connected detectors also alert a monitoring service that can dispatch emergency services if needed.

The most common type of vehicle carbon monoxide detector gets the job done through electrochemical sensors composed of electrodes submerged in an electrically conductive solution called an electrolyte. When carbon monoxide enters the gas-permeable compartment that houses the sensor, it triggers a chemical reaction that increases or decreases the current passing through the electrolyte. The exact amount by which the current increases tells the sensor the concentration of the noxious molecules present in the air. Other types of sensors work along similar lines by measuring the electrical resistance of a material. As carbon monoxide encounters the material, it lowers the material’s resistance to the flow of electricity to a degree that depends on the concentration of the contaminant.

On-the-Road Safety: Vehicle Carbon Monoxide Detectors for Automotive Use

A more sophisticated approach takes inspiration from hemoglobin, a protein in your blood cells that delivers oxygen to your tissues (but can be hijacked by carbon monoxide). In this version, a gel absorbs the deadly molecule and changes color, letting a light sensor know when it’s high-level CO nearby.

The detector’s on-vehicle diagnostic, or OBD, 16-pin connector enables it to interface with the vehicle’s computer system. A computing module in the device can then dictate instructions to the vehicle’s components to warn occupants when the carbon monoxide content of the air is dangerously high. The signals may be visual or audible, and different combinations of them are available to better suit a particular application.