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Measurement of VOCs for Air Quality Using Widely Tunable Mid-Infrared Laser Source Combined with Cantilever Enhanced Photoacoustic Detection

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  • 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

  • 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 Qu

    ality

  • AIR QUALITY POLLUTANTS

    - 3 -

    Contaminant Source Carbonmonoxide(CO) Incomplete combus7on infireplaces, ovens andotherhea7ngappliances, and tobacco

    smoking Carbondioxide(CO2) Themetabolismofbuildingoccupantsandpets. Nitrogenoxides(NOx) Sideproductof combus7on. Indoor sources: gasfires, cookingandhea7ngappliances,

    smoking Indoor-generatedpar7culatemaFeranddust Carpets, tex7les, food, animal and plant proteins in dust, and occupants (especially in

    buildingswithahighdensityofoccupants) Vola/leorganiccompounds(VOCs) Allman-madebuildingmaterialsemitVOCs,especiallywhennewordamaged.

    Cleaningproducts. Formaldehyde Buildingmaterials,par/cleboards,householdchemicals,ETS,andcarpetsand

    otherhouseholdtex/les. Man-mademineralfibres(MMMF) MMMFareusedininsula7onmaterials,andacous7clinings.Fibresareirritants. Mould (fragments, mouldy material, spores, microbialVOCs)

    Mouldgrowthdependsonmoisture:wetstructures,waterleakages,condensa7on,highindoorhumidity

    Limonene Freshners,Cleaningproducts,Personalcareproducts InorganicIons Cooking,Smoking Metals Cooking,Smoking,Dust Elementalcarbon(EC),OrganicCarbon(OC) Cooking,Smoking,Dust

    PAHs(PolycyclicAroma7cHydrocarbons) Buildingmaterials,Fiberboard,Chipboard,Dust,Cooking,Smoking PCBs(PolychlorinatedBiphenyls) Buildingmaterials,Fiberboard,Chipboard PBDEs(PolybrominatedDiphenylEthers) Plas7cizers,flameretardants

    March 2017

  • TECHNOLOGY & INVENTIONS

  • 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

    Gaseras 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

  • GASERAS 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

  • CONCEPT

    March 2017

    Sensi/vityPatentedcan7leversensorReliabilityPhotoacous7cprincipleVersa/litycanbecombinedwithdifferenttypesoflightsources(NIR-TDL,DFB-QCL,EC-QCL,OPO,BroadbandIRandfilters)

  • 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-QCL OPO

  • CASE STUDIES

  • 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

  • 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 g/m3) for 1 min measurement time

  • 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)

  • 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)

  • 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)

  • FORMALDEHYDE WITH DFB-QCL

    Detection limit (1) is 3 ppb for 1-minute response time and 1 ppb for 10-minute response time.

  • 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

  • CONTACT AND FOLLOW Lemminkisenkatu 59

    20520 Turku Finland

    [email protected] [email protected] www.gasera.fi

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