A sensor for gaseous and vaporous species is disclosed. The sensor comprises an electrically insulated substrate which contains small pores passing completely through it. Electrodes consisting of metallic or semiconductor material are deposited onto the top surface of the substrate. In a first embodiment of the invention, an electrolyte is placed on the top surface of the substrate in such a manner as to create a gas or vapor permeable electrolyte layer on top of the electrodes. In a second embodiment of the invention, the electrolyte is applied to the bottom surface of the substrate and seeps up through the porous holes of the substrate until it makes contact with the electrodes. Both embodiments result in a gas sensor with a response time dependent upon the gas flow rate rather than the time required for the gas to be dissolved in the electrolyte layer and be detected.