Abstract: Elementary electrodes with at least two characteristic dimensions smaller than 1 ?m or 2.5 ?m, including a reactive surface, with characteristic dimensions smaller than 1 ?m or 2.5 ?m, a thin film of catalyst, part of the surface of which is comprised in the reactive surface, a thin film of carbon, in an allotropic form of carbon chosen from boron-doped diamond and nitrogen-doped amorphous non-hydrogenated carbon, in contact with the said thin film of catalyst and part of the surface of which is included in the reactive surface, a support, in contact with at least one of the thin films, enabling electrical measurements.

Abstract: In the field of monitoring air quality, and more specifically, the field of identification of the presence of gaseous chemical pollutants such as volatile organic compounds, in an enclosed environment, there is disclosed a system including: a substrate; a gaseous chemical pollutant sensor; and at least one colorimetric marker of a predetermined colour situated on the substrate.