Measurement of VOCs for Air Quality Using Widely Tunable Mid-Infrared Laser Source Combined with Cantilever Enhanced Photoacoustic Detection
•
2 likes•865 views
Indoor Air Quality Indoor air quality has a large impact on health, quality of life and work efficiency. Numerous indoor air impurities are responsible for respiratory diseases , allergies, intoxication and certain types of cancer. Contaminants are caused by e.g. moulds, decomposing floor covering, tobacco smoke, outgassing from furniture. Photoacoustic detection combined with widely tunable mid-IR laser sources provides a versatile platform for various air quality applications. High-power EC-QCL in the fingerprint regions enables measurement of many VOCs and also other gases that typically are active in the common fingerprint region. Easy to operate, miniaturization possibilities and infrequent maintenance requirement provides additional benefit.
Report
Share
Measurement of VOCs for Air Quality Using Widely Tunable Mid-Infrared Laser Source Combined with Cantilever Enhanced Photoacoustic Detection
- 1. Measurement of VOCs for Air Quality Using Widely Tunable Mid-Infrared Laser Source Combined with Cantilever Enhanced Photoacoustic Detection Jussi Raittila, CTO, Gasera Ltd. Pittcon 2017, 8. March 2017, 10:05 am
- 2. Indoor air quality - 2 - • Most people spend approximately 80% to 90% of their time indoors • Indoor air quality has a large impact on health, quality of life and work efficiency • Numerous indoor air impurities are responsible for respiratory diseases , allergies, intoxication and certain types of cancer • Contaminants are caused by e.g. moulds, decomposing floor covering, tobacco smoke, outgassing from furniture Indoor Air Quality
- 3. AIR QUALITY POLLUTANTS - 3 - Contaminant Source Carbon monoxide (CO) Incomplete combus7on in fireplaces, ovens and other hea7ng appliances, and tobacco smoking Carbon dioxide (CO2) The metabolism of building occupants and pets. Nitrogen oxides (NOx) Side product of combus7on. Indoor sources: gas fires, cooking and hea7ng appliances, smoking Indoor-generated par7culate maFer and dust Carpets, tex7les, food, animal and plant proteins in dust, and occupants (especially in buildings with a high density of occupants) Vola/le organic compounds (VOCs) All man-made building materials emit VOCs, especially when new or damaged. Cleaning products. Formaldehyde Building materials, par/cle boards, household chemicals, ETS, and carpets and other household tex/les. Man-made mineral fibres (MMMF) MMMF are used in insula7on materials, and acous7c linings. Fibres are irritants. Mould (fragments, mouldy material, spores, microbial VOCs) Mould growth depends on moisture: wet structures, water leakages, condensa7on, high indoor humidity Limonene Freshners, Cleaning products, Personal care products Inorganic Ions Cooking, Smoking Metals Cooking, Smoking, Dust Elemental carbon (EC), Organic Carbon (OC) Cooking, Smoking, Dust PAHs (Polycyclic Aroma7c Hydrocarbons) Building materials, Fiberboard, Chipboard, Dust, Cooking, Smoking PCBs (Polychlorinated Biphenyls) Building materials, Fiberboard, Chipboard PBDEs (Polybrominated Diphenyl Ethers) Plas7cizers, flame retardants March 2017
- 5. PHOTOACOUSTIC SPECTROSCOPY • Photoacoustic effect was discovered in 1880 by Alexander Graham Bell • This theoretical potential has not been reached, since conventional microphones have been used for sensing the pressure pulses • Gasera’s novel cantilever sensor technology allows the use of the full potential of the photoacoustic phenomena Photoacoustic spectroscopy is based on the absorption of light leading to the local warming of the absorbing volume element. The subsequent expansion of the volume element generates a pressure wave proportional to the absorbed energy, which can be detected via a pressure detector. PHOTOACOUSTIC GAS CELL IR SOURCE MICROPHONE IR FILTER CHOPPER A typical setup of a conventional PAS system GAS SAMPLE
- 6. GASERA’S KEY INVENTIONS • Cantilever sensor • Over 100 times greater physical movement can be achieved compared to conventional microphone membrane • Highly linear response • Optical readout system • Contactless optical measurement based on laser interferometry • Measures cantilever displacements smaller than picometer (10-12 m) • Extremely wide dynamic measurement range
- 8. POWERFUL LASER SOURCES FOR VOC DETECTION March 2017 • Two common VOC fingerprint region can be accessed by either an OPO or an EC-QCL • Both OPO and EC-QCL have fairly similar optical characteristics, although the operational principle is completely different • OPO has slightly better output power whereas EC-QCL has a broader tuning range • For a complex VOC matrix, EC-QCL enables more selective detection of multiple gases due to more isolated spectral features EC-QCLOPO
- 9. CASE STUDIES
- 10. BTX MEASUREMENT WITH OPO • OPO source from Cobolt AB • Sample concentrations about 10 ppm • Pulsed OPO (100 mW) + Gasera PA201 (discrete sampling) • Detection limits approx. 10 ppb @ 1 second for all compounds • Multivariate DL below 1 ppb PNNL Photoacoustic
- 11. VOC FROM FLOOR COVERING WITH OPO • The damage in the floor coverings due to moisture is a common indoor air problem • The emissions of the damaged coverings lead often to several symptoms to the users of the building. • 2-ethyl-1-hexanol (2-EH) is the marker compound for the damage • Present analysis methods are expensive, time-consuming, limited and unreliable • Photoacoustic spectrum between 3398-3458 nm was recorded using a pulsed OPO as a source • The spectral shape of 2-EH can be clearly identified in the measured floor covering sample • Detection limit of the setup for 2-EH is 125 ppt (0.67 µg/m3) for 1 min measurement time
- 12. UNKNOWN GAS WITH EC-QCL • A case of an impurity in the air of a production plant • A clear impurity was recognized in the measured spectrum • Impurity was identified as methanol (fingerprint) • The methanol concentration was 3 ppm • Detection limit was 0.9 ppb (60 s)
- 13. ETHANOL WITH EC-QCL • Detection of EtOH in the presence of water and two other target gases is both selective and sensitive • Detection limit is in the low- ppb level (60 s) for EtOH and two other target gases (VOC and non-VOC)
- 14. VOCs WITH EC-QCL • Multi-gas analysis for air quality measurements • Tuning range: 1000 – 1250 cm-1 • Resolution: 1 cm-1 • 3 minutes response time • ppb-level detection limits (1 – 26 ppb with analysis)
- 15. FORMALDEHYDE WITH DFB-QCL Detection limit (1σ) is 3 ppb for 1-minute response time and 1 ppb for 10-minute response time.
- 16. CONCLUSIONS • Photoacoustic detection combined with widely tunable mid-IR laser sources provides a versatile platform for various air quality applications • High-power EC-QCL in the fingerprint regions enables measurement of many VOCs and also other gases that typically are active in the common fingerprint region • Easy to operate, miniaturization possibilities and infrequent maintenance requirement provides additional benefit
- 17. CONTACT AND FOLLOW • Lemminkäisenkatu 59 20520 Turku Finland • contact@gasera.fi • firstname.lastname@gasera.fi • www.gasera.fi • www.facebook.com/gaseraltd • www.youtube.com/gaseraltd • https://www.linkedin.com/company/ gaseraltd • @gaserafinland • slideshare.net/gasera