Abstract: There is presented an electrochemical sensor (100) for sensing nitrous oxide (N2O) in an associated volume (106), the sensor comprising a primary chamber (110), a secondary chamber (120) being placed adjacent the primary chamber (110), the secondary chamber (120) comprising electrodes for performing electrochemical measurements and furthermore an electrolyte comprising an aprotic solvent. A first membrane (114) and a secondary membrane (124) are permeable to nitrous oxide and may be arranged so as to separate the associated volume (106) from a primary volume (116) within the primary chamber (110), and the primary volume (116) from a secondary volume (126) within the secondary chamber (120), where the primary chamber (110) comprises means for hindering oxygen in passing into the secondary volume (126), and wherein the working electrode (104) comprises indium (In).