Abstract: The invention relates to a device (10) for detection of harmful substances with a measurement unit (28) for measuring at least one harmful substance and an evaluation unit (30) for determining the concentration of the at least one harmful substance. The invention also relates to a method for detecting harmful substances in a gas mixture. It is hereby provided that the gas mixture is tested for a gaseous harmful substance or simultaneously for several gaseous harmful substances, wherein the gaseous harmful substance or the gaseous harmful substances is/are measured with different sensor means, and the gaseous harmful substances are optionally chemically modified such that a measurement is performed with the existing sensor means.