Gasera - Model ONE HF - Hydrogen Fluoride Gas Monitor - Brochure

1 // 2 Application The exceptional moisture under the covering results in the chemical degradation of the flooring and its adhesive. Among other emissions, which are mostly Volatile Organic Com- pounds (VOC), there are some indicator compounds reveal- ing the damage: 2-ethyl-1-hexanol (2-EH) in older coverings and C9 alcohols in newer coverings. In case the flooring damage is not obvious by sensory ob- servations or moisture measurements, the condition of the flooring is investigated by VOC sampling of the indoor air or Field and Laboratory Emission Cell (FLEC) emission meas- urements on the surface of the covering. The sampling is very time-consuming and expensive, and therefore the amount of samples is usually limited even though the surface area, where the damages are suspected is usually large. Typically, the laboratory analysis of the samples takes several weeks. Therefore, costly and purposeless renovations are often made on the basis of few individual samples. This generates a need for a portable analyzer for fast on-site analysis. Technology The detection limits of the indoor air VOC sampling meth- ods depend on the investigated compound and are usually in the range of 0.1-1 µg//m3. The inaccuracy of the analysis method is about 20 – 30 % without the inaccuracy of sam- pling included. Extremely low detection limits set a need for an ultra-sensitive detection technique. The damage in floor coverings due to exceptional moisture is a common indoor air problem in both new and old buildings. The emissions of the damaged coverings often lead to several, mostly irritational symptoms to the users of the building. At present, the technologies used to detect the emissions are time-consuming, expensive and unreliable. The capability of Gasera LP1 portable analyzer in this application was demonstrated by rapid headspace detection of the emissions of a damaged floor covering sample. APPLICATION NOTE LP1 Analysis of damaged floor coverings emissions in indoor air quality Fig. 2. Odin Series tunable mid-infrared optical parametric oscillator from Cobolt AB. Fig. 1. Gasera LP1 laser-based portable photoacoustic gas analyzer. 2 // 2 Gasera Ltd. | Tykistökatu 4, 20520 Turku, FINLAND | www.gasera.fi | sales@gasera.fi The LP1 analyzer is designed to accommodate various in- frared sources for different applications. The strongest ab- sorption features of 2-EH are between 3300 and 3600 nm. A compact widely tunable optical parametric oscillator (OPO) from Cobolt AB is the best available infrared source for that region and was chosen for this application. The exceptional sensitivity and wide dynamic range of the patented optical cantilever microphone of the LP1 is combined with the high selectivity of the OPO. Measurements The performance of the LP1 is quantified by first measur- ing a pure 2-EH sample and calculating the detection limit, and then demonstrated measuring the emissions of an actual damaged floor covering sample. The technical details of the instrument and parameters used in the measurements are shown in Table I. Table I. Technical details and measurement parameters A calibrated 21 mg//m3 (4 ppm) sample of 2-EH was meas- ured with the LP1 analyzer to determine the detection limit. The measured photoacoustic spectrum and a PNNL library spectrum are displayed in Fig 3. Fig. 3. Measured photoacoustic spectrum of 2-EH plot- ted with a PNNL library spectrum. A good match between the measured and library spectrum is achieved. The detec- tion limit is in the sub-ppb range with a fast response time. The measured photoacoustic spectrum of 2-EH match- es well with the PNNL library spectrum. The detection limit was calculated from an average of three consecu- tive 2-EH measurements and the noise level of the ana- lyzer was quantified by calculating the root-mean-square (RMS) noise from a measured synthetic air background (zero-gas). The calculated detection limit of 2-EH (2xRMS) for 1 min measurement time was 0.67 µg//m3 (0.125 ppb), which is in the same range as the VOC sampling methods. The true test, however, is how well the analyzer performs with real covering samples. The emissions of a damaged floor covering sample from a property that has known indoor air quality issues was measured with the LP1. The measured spectrum is shown in Fig. 4 as well as the previously meas- ured spectrum of pure 2-EH. The spectral shape of 2-EH can be clearly identified in the measured floor covering sample. The additional features in the spectrum of the covering, for example between 3400-3415 nm and peaks in 3433 and 3455 nm are due to water vapor present in the headspace. Very good signal-to-noise ratio (SNR) with no interference from other emitted compounds was achieved with a fast head- space measurement with LP1. Fig. 4 Measured photoacoustic headspace spectrum of a damaged floor covering sample. The sample emits mostly 2-EH, which can be observed when comparing to the measured spectrum of pure 2-EH. Additional features in the spectrum between 3400-3415 nm, and in 3433 and 3455 nm are due to water vapor present in the headspace. Conclusion Cantilever-enhanced photoacoustic spectroscopy can meet the requirements for sensitivity, and the technology can be packed to portable size. The sensitivity and selectivity of the analysis comes from the combination of optical cantilever microphone and powerful optical parametric oscillator. Sub- ppb level detection limits for 2-ethyl-1-hexanol as well as a succesful measurement of an actual floor covering sample were demonstrated for a reliable floor coverings analysis. Laser output power 85-90 mW Laser wavelength tuning range 3398-3458 nm Laser dimensions 125 x 70 x 45 mm Modulation frequency 70 Hz PA cell length 100 mm PA cell pressure 1010 mbar PA cell temperature 50 °C Detection limit (2xRMS) of 2-EH (1 min measurement) 0.125 0.67 ppb µg//m3