To achieve gas detection in a precise and reliable way, but at the same time without consuming too much energy, a gas detection system is provided which generally comprises a pair of two different gas detectors. The first detector (DLP) is active continuously and sense substantially for an unspecific change in the local gas mixture. As a reaction upon the change, the second detector (DHP) of the pair is activated. This detector (DHP) performs the determination of the concentration of a specific gas or several specific gasses. The second detector (DHP) may be of a type which consumes more power, but will be active for a short period of time before returning to an inactive state where only the first detector (DLP) is active. The first detector (DLP) however is of a type using little power.