Photoacoustic Spectroscopy in Trace Gas Monitoring

Abstract Gas‐phase spectroscopy is nowadays very common in a wide variety of fields next to chemistry and physics, ranging from atmospheric chemistry to biology, medical sciences, and safety. Spectroscopic gas sensors have proven to be indispensable tools for these areas. There are various ways of utilizing gas sensors, and each application puts different demands. Some applications require a very high sensitivity for one specific gas compound, while others benefit more from a sensor that has the ability to measure a wide range of gases or benefit from a miniaturized footprint. A high time resolution is also desirable, as well as selectivity, robustness, and little or no need for sample preparation and maintenance; photoacoustic spectroscopy and their sensors meet a large number of these demands. This article discusses photoacoustic spectroscopy as sensitive, real‐time, and noninvasive tool for trace gas monitoring. After an introduction and historic overview, attention is focused onto the description of devices and equipment; they determine the detection limits and selectivity. Applications are discussed with emphasis on atmospheric applications, safety, and biological/agricultural applications followed by human health examples. Finally, a comparison is made with other spectroscopy methods.