Carbon monoxide detectors: how they work

In short: A carbon monoxide detector, or CO detector, sounds a loud alarm when a dangerous amount of carbon monoxide builds up in the air of a room. This matters because the gas can neither be seen nor smelled.

In more detail: Carbon monoxide forms when fuels such as gas, oil, wood or coal burn incompletely. A smoke alarm does not detect it, so rooms with combustion appliances need a separate device.

In detail

• Invisible danger: Carbon monoxide is colourless, odourless and tasteless and binds to the red blood pigment much more strongly than oxygen does, so the organs receive too little oxygen.
• Typical sources: Faulty or poorly ventilated gas boilers, fireplaces, stoves and gas water heaters, as well as charcoal barbecues, which must never be used indoors.
• Sensor: Most devices use an electrochemical sensor in which carbon monoxide triggers a chemical reaction that produces a measurable electric current.
• Triggering the alarm: The detector assesses both the concentration and how long it lasts; at high levels it sounds the alarm quickly, at low levels only after a longer time.
• Where to fit it: Detectors make sense in the room with the combustion appliance and in bedrooms; height and distance follow the instructions for the particular device.
• Maintenance: Press the test button regularly and replace the device once its stated lifespan has expired, because the sensor weakens over time.
• If the alarm sounds: Immediately open windows and doors, switch off the appliance if possible, get all people and animals outside and call the emergency number 112, especially if anyone has a headache, dizziness or nausea.
• No substitute for servicing: A CO detector does not replace regular inspection of the heating system and flue by professionals such as chimney sweeps or heating engineers (rauchmelder-und-brandschutz-im-haushalt, rauchgas-und-co-vergiftung, gasgeruch-und-gasleck-richtig-reagieren).