Many gases that contribute to global air pollution can be detected by means of infrared absorption. But commercial IR spectrometers are usually cumbersome and expensive, so they can only be used as stationary equipment in a lab. A Fraunhofer EMFT research team is currently developing a portable IR multi-gas analyzer for mobile use. The compact system runs on batteries if necessary, and the measurements can be transfered directly for display on a tablet or laptop.
This enables analyses to be carried out directly on site so as to trace soil contamination or historical pollution such as solvents or petroleum-derived hydrocarbons. The device operates in the wavelength ranges of 3.1 μm - 4.4 μm and 5.5 μm - 8.0 μm, covering the absorption of more than 60 harmful gas types relevant to the environment such as carbon dioxide, hydrogen sulphide and methane. By creating a 200 mm absorption path featuring gas-proof sealing by means of CaF2 window, the development team was able to strike a sound compromise between size and sensitivity. Due to an internal reference gas generation function by means of filtering ambient air, the system does not require synthetic air for operation purposes. By means of automatically controlled membrane pumps, the reference and sample gas are successively put through the absorption path and subjected to spectral analysis. Then the resulting absorption spectrum is calculated based on the two measurements.