Indicator tubes allow us to quickly identify the main chemical substances in the air. The drawback lies in the relatively high measurement uncertainty and the need to know the type of pollutants. This method is suitable for periodic inspections of a given production facility when we have information about all emitted substances. In a dynamic and unfamiliar environment, it is very difficult to predict both the type and concentration of the substances. This method is widely used due to the relatively low cost of consumables and sampling equipment, as well as the quick training of personnel.
Infrared spectroscopy.
Infrared spectroscopy is a technology used for chemical analysis and determining the molecular structure of solids, liquids, and gases.
Absorption spectroscopy (FTIR, UV-Vis, etc.) can be used to determine how substances absorb light in a given wavelength range.
FTIR—Fourier transform infrared spectroscopy—is a branch of infrared spectroscopy. Every molecular structure has a unique combination of atoms. When molecules are irradiated in the infrared region of the electromagnetic spectrum, they begin to vibrate and absorb infrared rays at precisely defined frequency spectra. It is precisely by determining the absorption peaks of the gases being analyzed and depending on the frequency range of absorption that the type and concentration of the substance being analyzed are determined. Every molecular structure has a characteristic absorption region. Matrices—reference spectra of the substances—are entered into the analyzers, thereby automatically determining the type of hundreds of pollutants. The case of determining the type and concentration of a multicomponent gas mixture—or, in other words, the presence of multiple pollutants in the sample—is more complex. The absorption spectrum is quite complex because it consists of several peaks, and knowledge and experience are required to identify the pollutants.
Portable gas analyzers are available that detect gas components using the FTIR method. This method is used to identify both organic and inorganic gas mixtures. Results can be transmitted in real time from sampling sites to remote workstations staffed by highly qualified specialists with experience in spectroscopic measurements. The devices are useful for rapid analysis in unfamiliar environments and for unknown contaminants—such as industrial accidents, fires, and in the presence of substances for which the use of a linear colorimetric method with indicator tubes is impossible. The technology is also applied to air emission measurements from point sources—thermal power plants, incinerators, cement plants, and chemical plants. The main industrial pollutants are measured in ppm or ppb: CO, NO, NO2, formaldehyde, NH3, SO2, N2O, HCl, HF, CH4, and others.
Useful Links
https://www.gasmet.com/
https://en.wikipedia.org/wiki/Fourier-transform_infrared_spectroscopy
https://www.thermofisher.com/bg/en/home/industrial/spectroscopy-elemental-isotope-analysis/spectroscopy-elemental-isotope-analysis-learning-center/molecular-
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