Gas sensor and method for its preparation

The invention relates to a gas sensor for detecting gases in the air, in particular formaldehyde. The sensor has at least one gas-sensitive region, which preferably is a layer on a substrate and contains In For the preparation of the gas-sensitive region of the flame spray pyrolysis (FSP) is used, are used as starting materials organometallic compounds of indium and tin. The gas sensor is particularly suitable for online gas detection.