Analysis of damaged floor coverings emissions in indoor air quality with cantilever-enhanced

photoacoustic spectroscopy

Dr. Ismo Kauppinen, CEO, Gasera Ltd. Pittcon 2016, 8. March 2016, 10:25 pm Gasera Ltd. Tykistökatu 4, 20520 Turku, Finland

Indoor air quality

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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 moulds, decomposing floor covering, tobacco smoke, outgassing from furniture

Indoor Air Quality

Air quality pollutants

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Contaminant Source Carbon monoxide (CO) Incomplete combustion in fireplaces, ovens and other heating appliances, and

tobacco smoking Carbon dioxide (CO2) The metabolism of building occupants and pets. Nitrogen oxides (NOx) Side product of combustion. Indoor sources: gas fires, cooking and heating

appliances, smoking Indoor-generated particulate matter and dust Carpets, textiles, food, animal and plant proteins in dust, and occupants

(especially in buildings with a high density of occupants) Chemicals, volatile organic compounds (VOCs) All man-made building materials emit VOCs, especially when new or damaged.

Cleaning products. Formaldehyde Building materials, particle boards, household chemicals, ETS, and carpets and

other household textiles. Man-made mineral fibres (MMMF) MMMF are used in insulation materials, and acoustic linings. Fibres are irritants. Mould (fragments, mouldy material, spores, microbial VOCs)

Mould growth depends on moisture: wet structures, water leakages, condensation, 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 Aromatic Hydrocarbons) Building materials, Fiberboard, Chipboard, Dust, Cooking, Smoking PCBs (Polychlorinated Biphenyls) Building materials, Fiberboard, Chipboard PBDEs (Polybrominated Diphenyl Ethers) Plasticizers, flame retardants

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Floor coverings degrade if installed on concrete that has not been dried enough In some cases, the coverings are installed on wet concrete on purpose to avoid contractual penalties due to delays in construction projects This happens frequently Typically the problems do not appear immediately

Reasons for floor coverings emissions

Current solution for floor coverings emissions detection techniques

Field and Laboratory Emission Cell (FLEC)

A hood to collect VOCs over a long time period

The sample is analyzed in laboratory afterwards

Time-consuming & expensive which limits the number of samples taken

Laboratory analysis of the samples takes usually weeks

Often the laboratory analysis result is useless because of leaking during the sampling

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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 spectroscopy

PHOTOACOUSTIC GAS CELL IR SOURCE

MICROPHONE

IR FILTER

CHOPPER

A typical setup of a conventional PAS system

GAS SAMPLE

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Key inventions Cantilever sensor

  Over 100 times greater physical movement can be achieved compared to conventional microphone membrane – cantilever has very low string constant 1 N/m

  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

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Benefits of cantilever enhanced PAS

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stability , reliability, easy to use Absorption is measured directly in PAS, which makes the measurement very accurate and free of drift

below ppb detection limits Cantilever sensor provides high sensitivity

wide linear dynamic range, miniaturization, low sample volume Sensitivity is not dependent on the optical path length

multi-gas capability Many different sources can be connected to one cell

suitable to wide range of process applications Possibility to heat the sample cell

Concept

Sensitivity – Patented cantilever sensor

Reliability – Photoacoustic principle

Versatility – can be combined with different types of light sources (NIR-TDL, DFB-QCL, EC-QCL, OPO, Broadband IR and filters)

Selection of the source

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Optical microphone DSP unit

Laser driver

TEC controller

Readout interferometer

Sample cell

Cantilever

OPO source

Aspheric lens Laser beam

Beam dump

Gas

IN

Gas

OU

T

Balance cell

Gas exchange controller

Gas exchange unit

Gas valves

Proposed measurement setup

Typically 10 cm or less

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Analysis of damaged floor coverings emissions

•  2-ethyl-1-hexanol (2-EH) is the marker compound for the damage

•  Photoacoustic spectrum of 2-EH in nitrogen background between 3398-3458 nm was recorded using a pulsed OPO as a source

•  The spectral shape of measured spectrum matches well with the PNNL library spectrum

•  Detection limit of the setup for 2-EH is 125 ppt (0.67 µg/m3) for 1 min measurement time

•  Same detection limit level than with time-consuming laboratory techniques was achieved

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Analysis of real samples

•  A floor covering sample from a building with known indoor air quality issues was measured

•  Emissions of the sample were measured with a headspace measurement

•  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

•  Other features in the spectrum are due to moisture

•  The sample strongly emits 2-EH but very little other VOCs that are absorbing in this 3398-3458 nm region

•  High sensitivity and selectivity can be achieved

Thank you!

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