{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T19:11:14Z","timestamp":1787771474251,"version":"build-2784847793"},"reference-count":40,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2025,1,22]],"date-time":"2025-01-22T00:00:00Z","timestamp":1737504000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this work, a highly sensitive, selective, and industrially compatible gas sensor prototype is presented. The sensor utilizes three distributed-feedback quantum cascade lasers (DFB-QCLs), employing wavelength modulation spectroscopy (WMS) for the detection of hydrogen sulfide (H2S), methane (CH4), methyl mercaptan (CH3SH), and carbonyl sulfide (COS) in the spectral regions of 8.0 \u00b5m, 7.5 \u00b5m, and 4.9 \u00b5m, respectively. In addition, field-programmable gate array (FPGA) hardware is used for real-time signal generation, laser driving, signal processing, and handling industrial communication protocols. To comply with on-site safety standards, the QCL sensor prototype is housed in an industrial-grade enclosure and equipped with the necessary safety features to ensure certified operation under ATEX\/IECEx regulations for hazardous and explosive environments. The system integrates an automated gas sampling and conditioning module, alongside a purge and pressurization system, with intrinsic safety electronic components, thereby enabling reliable explosion prevention and malfunction protection. Detection limits of approximately 0.3 ppmv for H2S, 60 ppbv for CH3SH, and 5 ppbv for COS are demonstrated. Noise-equivalent absorption sensitivity (NEAS) levels for H2S, CH3SH, and COS were determined to be 5.93 \u00d7 10\u22129, 4.65 \u00d7 10\u22129, and 5.24 \u00d7 10\u221210 cm\u22121 Hz\u22121\/2. The suitability of the sensor prototype for simultaneous sulfur species monitoring is demonstrated in process streams of a hydrodesulphurization (HDS) and fluid catalytic cracking (FCC) unit at the project\u2019s industrial partner, OMV AG.<\/jats:p>","DOI":"10.3390\/s25030635","type":"journal-article","created":{"date-parts":[[2025,1,22]],"date-time":"2025-01-22T05:50:53Z","timestamp":1737525053000},"page":"635","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["ATEX-Certified, FPGA-Based Three-Channel Quantum Cascade Laser Sensor for Sulfur Species Detection in Petrochemical Process Streams"],"prefix":"10.3390","volume":"25","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6503-854X","authenticated-orcid":false,"given":"Harald","family":"Moser","sequence":"first","affiliation":[{"name":"Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9\/164, 1060 Vienna, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0291-487X","authenticated-orcid":false,"given":"Johannes Paul","family":"Waclawek","sequence":"additional","affiliation":[{"name":"Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9\/164, 1060 Vienna, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Walter","family":"P\u00f6lz","sequence":"additional","affiliation":[{"name":"OMV AG, Mannsw\u00f6rther Stra\u00dfe 28, 2320 Schwechat, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3838-5842","authenticated-orcid":false,"given":"Bernhard","family":"Lendl","sequence":"additional","affiliation":[{"name":"Institute of Chemical Technologies and Analytics, TU Wien, Getreidemarkt 9\/164, 1060 Vienna, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,1,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1016\/j.trac.2011.08.008","article-title":"A review of sensor-based methods for monitoring hydrogen sulfide","volume":"32","author":"Pandey","year":"2012","journal-title":"TrAC\u2014Trends Anal. Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"198","DOI":"10.1039\/C3AN01793A","article-title":"Monitoring of hydrogen sulfide via substrate-integrated hollow waveguide mid-infrared sensors in real-time","volume":"139","author":"Petruci","year":"2014","journal-title":"Analyst"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1007\/s00340-016-6355-6","article-title":"Cantilever-enhanced photoacoustic detection of hydrogen sulfide (H2S) using NIR telecom laser sources near 1.6 \u00b5m","volume":"122","author":"Moser","year":"2016","journal-title":"Appl. Phys. B"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"100997","DOI":"10.1016\/j.pecs.2022.100997","article-title":"Laser sensors for energy systems and process industries: Perspectives and directions","volume":"91","author":"Farooq","year":"2022","journal-title":"Prog. Energy Combust. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1016\/j.jare.2020.05.018","article-title":"Emerging analytical tools for the detection of the third gasotransmitter H2S, a comprehensive review","volume":"27","author":"Ibrahim","year":"2021","journal-title":"J. Adv. Res."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"771","DOI":"10.1016\/S0039-9140(00)00421-5","article-title":"Analytical strategies for the detection of sulfide: A review","volume":"52","author":"Lawrence","year":"2000","journal-title":"Talanta"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Vargas, A.P., G\u00e1mez, F., Roales, J., Lopes-Costa, T., and Pedrosa, J.M. (2021). A paper-based ultrasensitive optical sensor for the selective detection of H2 S vapors. Chemosensors, 9.","DOI":"10.3390\/chemosensors9020040"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.cattod.2010.05.011","article-title":"Recent advances in the science and technology of ultra low sulfur diesel (ULSD) production","volume":"153","author":"Stanislaus","year":"2010","journal-title":"Catal. Today"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"553","DOI":"10.1126\/science.264.5158.553","article-title":"Quantum Cascade Laser","volume":"264","author":"Faist","year":"1994","journal-title":"Science"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"165","DOI":"10.1007\/s00340-007-2846-9","article-title":"Application of quantum cascade lasers to trace gas analysis","volume":"90","author":"Kosterev","year":"2007","journal-title":"Appl. Phys. B"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.cplett.2009.12.073","article-title":"Quantum cascade lasers in chemical physics","volume":"487","author":"Curl","year":"2010","journal-title":"Chem. Phys. Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"111121","DOI":"10.1117\/1.3498770","article-title":"Applications of midinfrared quantum cascade lasers to spectroscopy","volume":"49","author":"Hancock","year":"2010","journal-title":"Opt. Eng."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"111124","DOI":"10.1117\/1.3498782","article-title":"Application of quantum cascade lasers to high-precision atmospheric trace gas measurements","volume":"49","author":"McManus","year":"2010","journal-title":"Opt. Eng."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"921","DOI":"10.1039\/b400914m","article-title":"Quantum cascade semiconductor infrared and far-infrared lasers: From trace gas sensing to non-linear optics","volume":"34","author":"Duxbury","year":"2005","journal-title":"Chem. Soc. Rev."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"A100","DOI":"10.1364\/AO.50.00A100","article-title":"External cavity tunable quantum cascade lasers and their applications to trace gas monitoring","volume":"50","author":"Rao","year":"2011","journal-title":"Appl. Opt."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"012004","DOI":"10.1088\/0957-0233\/24\/1\/012004","article-title":"Optical gas sensing: A review","volume":"24","author":"Hodgkinson","year":"2013","journal-title":"Meas. Sci. Technol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"261907","DOI":"10.1063\/1.4905281","article-title":"High power, widely tunable, mode-hop free, continuous wave external cavity quantum cascade laser for multi-species trace gas detection","volume":"105","author":"Centeno","year":"2014","journal-title":"Appl. Phys. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"131114","DOI":"10.1063\/1.4823545","article-title":"Sensitive trace gas detection with cavity enhanced absorption spectroscopy using a continuous wave external-cavity quantum cascade laser","volume":"103","author":"Lang","year":"2013","journal-title":"Appl. Phys. Lett."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"6165","DOI":"10.3390\/s140406165","article-title":"Quartz-Enhanced Photoacoustic Spectroscopy: A Review","volume":"14","author":"Patimisco","year":"2014","journal-title":"Sensors"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"189","DOI":"10.1016\/j.atmosenv.2015.04.010","article-title":"Simultaneous open-path determination of road side mono-nitrogen oxides employing mid-IR laser spectroscopy","volume":"112","author":"Ofner","year":"2015","journal-title":"Atmos. Environ."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1007\/s00340-006-2407-7","article-title":"Comparison of cw and pulsed operation with a TE-cooled quantum cascade infrared laser for detection of nitric oxide at 1900 cm\u22121","volume":"85","author":"McManus","year":"2006","journal-title":"Appl. Phys. B"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"257","DOI":"10.1364\/OL.38.000257","article-title":"Compact multipass optical cell for laser spectroscopy","volume":"38","author":"Tuzson","year":"2013","journal-title":"Opt. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"523","DOI":"10.1364\/AO.3.000523","article-title":"Off-axis paths in spherical mirror interferometers","volume":"3","author":"Herriott","year":"1964","journal-title":"Appl. Opt."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"718","DOI":"10.1364\/AO.31.000718","article-title":"Frequency modulation and wavelength modulation spectroscopies: Comparison of experimental methods using a lead-salt diode laser","volume":"31","author":"Bomse","year":"1992","journal-title":"Appl. Opt."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1277","DOI":"10.1016\/S0584-8547(01)00248-8","article-title":"Wavelength modulation absorption spectrometry\u2014An extensive scrutiny of the generation of signals","volume":"56","author":"Kluczynski","year":"2001","journal-title":"Spectrochim. Acta Part B At. Spectrosc."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1007\/s00340-009-3881-5","article-title":"Simulation-based comparison of noise effects in wavelength modulation spectroscopy and direct absorption TDLAS","volume":"100","author":"Lins","year":"2010","journal-title":"Appl. Phys. B"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"132082","DOI":"10.1016\/j.fuel.2024.132082","article-title":"Advancing hydrodesulfurization in heavy Oil: Recent developments, challenges, and future prospects","volume":"372","author":"Pham","year":"2024","journal-title":"Fuel"},{"key":"ref_28","first-page":"151","article-title":"Co-Processing of Atmospheric Residue With Vacuum Gas Oil in a Fluid Catalytic Cracking Pilot Plant\u2014Effects on Product Spectra and Carbonyl Sulfide Formation","volume":"135","author":"Swoboda","year":"2019","journal-title":"Erdoel Erdgas Kohle\/EKEP"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"729","DOI":"10.1007\/s00216-016-9923-z","article-title":"Implementation of a quantum cascade laser-based gas sensor prototype for sub-ppmv H2S measurements in a petrochemical process gas stream","volume":"409","author":"Moser","year":"2016","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Moser, H., Waclawek, J.P., Genner, A., Gasser, C., and Lendl, B. (2018, January 13\u201318). A triple quantum cascade laser based sulfur species sensor for H2S, CH3SH and COS in petrochemical process streams. Proceedings of the Conference on Lasers and Electro-Optics, San Jose, CA, USA.","DOI":"10.1364\/CLEO_AT.2018.AM2M.7"},{"key":"ref_31","first-page":"685","article-title":"Information-calculating system Spectroscopy of Atmospheric Gases. The structure and main functions","volume":"18","author":"Mikhailenko","year":"2005","journal-title":"Atmos. Ocean. Opt."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1016\/j.jqsrt.2013.07.002","article-title":"The HITRAN2012 molecular spectroscopic database","volume":"130","author":"Rothman","year":"2013","journal-title":"J. Quant. Spectrosc. Radiat. Transf."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"31329","DOI":"10.1364\/OE.495505","article-title":"Simple approach for spectral beam combination of narrowband laser sources for spectroscopic applications","volume":"31","author":"Moser","year":"2023","journal-title":"Opt. Express"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"023707","DOI":"10.1063\/1.4865841","article-title":"A high-bandwidth amplitude estimation technique for dynamic mode atomic force microscopy A high-bandwidth amplitude estimation technique for dynamic mode atomic force microscopy","volume":"85","author":"Karvinen","year":"2014","journal-title":"Rev. Sci. Instrum."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1109\/TASSP.1981.1163535","article-title":"An Economical Class of Digital Filters for Decimation and Interpolation","volume":"29","author":"Hogenauer","year":"1981","journal-title":"IEEE Trans. Acoust."},{"key":"ref_36","unstructured":"(2014). Explosive Atmospheres\u2014Part 2: Equipment Protection by Pressurized Enclosure \u201cp\u201d (Standard No. DIN IEC 60079-2:2014). German version EN 60079-2:2014."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"467","DOI":"10.1007\/s00340-008-3137-9","article-title":"Design considerations in high-sensitivity off-axis integrated cavity output spectroscopy","volume":"92","author":"Moyer","year":"2008","journal-title":"Appl. Phys. B"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Genner, A., Mart\u00edn-mateos, P., Moser, H., and Lendl, B. (2020). A quantum cascade laser-based multi-gas sensor for ambient air monitoring. Sensors, 20.","DOI":"10.3390\/s20071850"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"7794","DOI":"10.1364\/OE.416536","article-title":"Balanced-detection interferometric cavity-assisted photothermal spectroscopy employing an all-fiber-coupled probe laser configuration","volume":"29","author":"Waclawek","year":"2021","journal-title":"Opt. Express"},{"key":"ref_40","first-page":"1","article-title":"Direct High-Frequency Modulation of a Quantum Cascade Laser for High-Sensitivity Molecular Dispersion Spectroscopy at Ambient Pressure","volume":"73","author":"Giraud","year":"2024","journal-title":"IEEE Trans. Instrum. Meas."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/25\/3\/635\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,8]],"date-time":"2025-10-08T10:33:36Z","timestamp":1759919616000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/25\/3\/635"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,1,22]]},"references-count":40,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2025,2]]}},"alternative-id":["s25030635"],"URL":"https:\/\/doi.org\/10.3390\/s25030635","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,1,22]]}}}