A porous gold membrane working electrode was evaluated for amperometric sensing of NO or NO2 in air. The Au electrode was evaporated by E-beam onto a porous Teflon substrate and tested in two different geometries: a lab-built universal (U) and a housing (C) used in building sensors for commercial sale. The optimum bias for NO2 reduction was determined to be 2150 mV vs. Pt/air quasi-reference electrode (Pt/air-QRE) and was 1400 mV for NO oxidation. Sensor signals were independent of gas flow rate in both housings at flow rates over 30 cm(3)/min. NO sensitivity in the U and C housing was 180 and 43 nA/ppm, respectively, and the NO2 sensitivity was -100 and -38 nA/ppm, respectively. The U sensor had a limit of detection (LOD) for NO2 of 1.3 ppb (signal-to-noise ratio 3sigma). The sensor housing design and operating conditions can be directly related to observed analytical performance characteristics. (C) 2003 The Electrochemical Society.