As a Class 2B carcinogen, C<sub>8</sub>H<sub>8</sub> has great hidden danger to human health. Domestic research on the detection of styrene in the atmosphere is relatively lacking. Therefore, this article determined proper retrieval range of wavelength and a method to eliminate interference based on the absorption feature in the UV region. An open optical path detection system was set up based on the principle of ultraviolet differential absorption spectroscopy. The detection limit of C<sub>8</sub>H<sub>8</sub> is 9.0μg/m<sup>3</sup> when the optical path reaches 100m. The outdoor field measurement of C<sub>8</sub>H<sub>8</sub> was carried out in Binjiang District of Hangzhou, indicating the daily average variation of styrene gas. The results showed that the maximum concentration of C<sub>8</sub>H<sub>8</sub> is 60.6μg/m<sup>3</sup>, the minimum concentration is 38.2μg/m<sup>3</sup> and the average concentration is 53.5μg/m<sup>3</sup>.
An ultra-low emission Cl<sub>2</sub> monitoring optical system based on differential optical absorption spectroscopy has been set up. We have found through comparison experiments that UV reflection enhanced aluminum is damaged and the dielectric film mirror is intact under high concentration of Cl<sub>2</sub>. Then verify the performance characteristics of ultralow Cl<sub>2</sub> emission online monitoring device. The maximum absorbance of 50ppm Cl<sub>2</sub> exceeds 0.1, while the 30ppm Cl<sub>2</sub> reaches 0.063, so the measurement range can be 0-95 mg/m<sup>3</sup>, which meets the maximum allowable emission concentration of Cl<sub>2</sub> required by the new regulations for detection of 65mg/m<sup>3</sup>.
This paper describes a set of ultra-low smoke emission monitoring optical devices based on differential absorption spectroscopy (DOAS), which mainly includes a xenon lamp source, a sample cell, a spectrometer for light detection, and a Y-type optical fiber. The device utilizes a newly developed ultraviolet long path gas chamber, the energy of the ultraviolet spectrum is high, and the energy of the xenon lamp in the experiment is only enough to meet the application requirements. As well, based on DOAS optical device it has the advantages of high ultraviolet energy, small volume and high measurement accuracy. Therefore, the system solves the difficult problem of low concentration flue gas emission monitoring. The lower limit of detection of SO<sub>2</sub>, NO and NO<sub>2</sub> concentration was 0.21 mg/m<sup>3</sup>, 0.13 mg/m<sup>3</sup> and 0.61 mg/m<sup>3</sup>, respectively. Comparison of on-site field monitoring with high temperature FTIR (Fourier Transform Infrared Spectroscopy) flue gas emission monitor, the average concentrations of SO<sub>2</sub>, NO and NO<sub>2</sub> measured by the two instruments were less than 14 mg/m<sup>3</sup>, 39 mg/m<sup>3</sup> and 25 mg/m<sup>3</sup> respectively, and the correlations were all above 0.995.
In this paper, based on the analysis of the shortcomings of three-point comparison odor bag method, gas chromatography method and gas sensor, a malodorous gas monitoring device based on differential optical absorption spectroscopy (DOAS) is designed. This paper focuses on testing six gases, including carbon disulfide, styrene, dimethyl disulfide and so on. The total length of the optical path is 60cm. When the standard deviation is twice, the detection limit of these gases is around 0.10ppm. The results of mixed malodorous by measured show that the interference between components is very small, and the relative error of each component is less than 3% of the full scale by least square method. The odor gas emission monitoring device based on DOAS technology designed in this paper has the advantages of simple device and high measurement accuracy, which can meet the application requirements of field measurement.