检测有害气体的警报装置

防止泄漏的措施很多，在可动部件的转动处、滑动处、法兰连接等部位、清除口、安全阀、出口、排放管等处均应预防泄漏。而且，由于在定期检查、维修施工等情况下，操作现场的大气难以确保不受污染，所以，有害气体引起的危害性就进一步扩大。在这种情况下，对有害气体的检测大致可分为以下两个方面。     

有毒有害气体检测仪示值误差测量结果不确定度的评定

本文介绍了有毒有害气体检测仪示值误差测量结果不确定度的评定,并给出结果。     

火药燃烧有毒有害气体产物分析

在密闭容器中用SJ、GT火药模拟高能气体压裂不同燃烧压力下燃烧过程,通过红外光谱测定燃烧产物中有毒有害气体CO、NO的含量.结果表明:在高能气体压裂的压力范围内,SJ、GT火药CO的含量基本不受压力的影响,NO的含量随压力降低而增加;GT火药的燃烧产物中CO的含量低于SJ,NO的含量高于SJ.     

差分吸收光谱法在线测量排放烟气浓度研究

介绍了差分吸收光谱(DOAS)在线测量系统,分析了DOAS的光谱处理方法.研究了SO2气体浓度的DOAS测量方法,可以实现排放烟气中SO2的在线测量.DOAS法利用数学方法将吸收光谱分解成快变和慢变部分,他利用快变部分计算气体成分的浓度,这使得烟尘干扰和光源强度变化不影响烟气浓度测量精度.DOAS法用线测量代替点测量,可获得区域内更具有代表性的数据,能更准确的反映烟气排放情况;可同时对多种污染物的进行定性、定量分析;是非接触性测量,无需采样.     

资料影片库房内主要有害气体质量初步评价

本文通过对4个资料影片库房内的6种主要有害气体进行测定,取得了大量数据.采用大气质量指数评价模式中的普通单因子模式对4个库房内的有害气体质量进行了简单评价,对造成这4个库房有害气体质量评价结果的原因进行了分析.     

北京市居室几种常见有害气体全年污染水平调查

通过全年两月一次随机选择北京市共34处办公室和35处家居作为样点,按照国家标准方法采集氨、苯、甲醛、总挥发性有机化合物和氡几种常见有害气体,并进行浓度水平的分析,调查其污染水平及季节变化情况。结果表明:北京市室内环境中氨、甲醛和总挥发性有机化合物的超标现象严重,苯属轻度污染,氡完全符合室内环境质量标准。不同季节污染物水平表现出差异:甲醛浓度在7月最高,氨、苯浓度在9月最高,氡浓度在春季左右达到最高,总挥发性有机化合物成分复杂,随时间变化规律性不明显。     

非分散红外吸收光谱法空气痕量污染气体监测浓度算法

针对城市痕量污染气体检测中,所测气体浓度低、吸收弱,采用两点标定和高浓度标气定标造成吸收曲线误差增大的问题,本文提出了采用低浓度标气.多点定标的方法来获得吸收曲线的方法来建立吸收方程.该方法是基于比尔-朗伯吸收定律的吸收方程,当测量气体浓度较低时,其浓度和吸光度呈线性关系来完成.采用低浓度标气.多点定标两种方法的结合,来获得测量气体的吸收曲线.试验结果表明,有很高的测量精度.     

可燃及有害气体检测报警器的检定

<正>可燃气体检测报警仪也称测爆仪,它和有毒有害气体检测报警器广泛应用于焦化、化工、天然气、煤气等危险化学品场所中可燃性以及有害气体泄漏事故的检测报警,属于国家重点管理的工作用计量器具,国家早在20世纪90年代就陆续颁布了相关检定规程对它们实行法制管理。     

快速测量气体产品中PPm级氧浓度

<正>根据国家气体产品质量标准的规定,出厂气体产品必须进行严格抽检,对于氮、氩、氢、氦中氧的测定,往往由于操作不当,仪器性能欠佳,操作手续繁琐,难以测出满意结果,使厂家和用户都为之颇感费力。     

Assessment of multiphoton absorption in inert gases for the measurement of gas temperatures

A spatially resolved optical technique to measure gas temperature was assessed. The technique relies on multiphoton absorption in inert gases. In contrast to laser-induced fluorescence, absorption is insensitive to collisional deactivation, and, in contrast to one-photon absorption, multiphoton absorption only occurs around the focus point of a typical laser beam. Multiphoton absorption features both the merits of being insensitive to quenching and of being a spatially resolved technique. In a case study we assessed two-photon absorption in xenon upon exciting the 5p6 1S0-->5p56p[5/2]2 transition in xenon at a wavelength of 256 nm. The amount of light absorbed by xenon is related to the number density of the gas, and if the gas pressure is known then the gas temperature can be inferred from the number density. Two-photon absorbance was measured as a function of xenon number density and was used to validate a theoretical model of the absorption process. We discuss the circumnavigation of experimental challenges in applying this technique and analyze its precision in terms of the inferred gas temperature.     

Ground-based imaging differential optical absorption spectroscopy of atmospheric gases

We describe a compact remote-sensing instrument that permits spatially resolved mapping of atmospheric trace gases by passive differential optical absorption spectroscopy (DOAS) and present our first applications of imaging of the nitrogen dioxide contents of the exhaust plumes of two industrial emitters. DOAS permits the identification and quantification of various gases, e.g., NO2, SO2, and CH2O, from their specific narrowband (differential) absorption structures with high selectivity and sensitivity. With scattered sunlight as the light source, DOAS is used with an imaging spectrometer that is simultaneously acquiring spectral information on the incident light in one spatial dimension (column). The second spatial dimension is scanned by a moving mirror.     

Application of gas microstrip detectors for X-ray absorption spectroscopy in common process gases

We report upon the design of a new gas microstrip detector (GMSD) for use in X-ray absorption spectroscopy applied to the study of catalysis and material science. We show that GMSDs can operate not only with the gas mixtures normally used in proportional counters but also with the majority of gas mixtures used in common catalytic reactions. The detector functions well in the presence of water vapor. EXAFS investigations of a test system of NiO on Ni metal are discussed in which it is demonstrated that depth profiling using electron yield X-ray absorption spectroscopy is possible in a wide variety of gaseous environments. Electron detection of XAS using GMSDs is applicable to metals, semiconductors, and insulators presented in almost all forms of sample including films, pellets, powders, crystals, and liquids.     

Picosecond pump-probe absorption spectroscopy in gases: models and experimental validation

Picosecond pump-probe absorption spectroscopy is a spatially resolved technique that is capable of measuring species concentrations in an absolute sense without the need for calibrations. When laser pulses are used that are shorter than the collision time in a sample, this pump-probe technique exhibits reduced sensitivity to collisional effects such as electronic quenching. We describe modeling and experimental characterization of this technique. The model is developed from rate equations that describe the interactions of the pump and probe pulses with the sample. Calculations based on the density-matrix equations are used to identify limits of applicability for the model. Excellent agreement between the model and the experimental data is observed when both 1.3- and 65-ps pulses are used to detect potassium in a flame and in an atomic vapor cell.     

Extension of wavelength-modulation spectroscopy to large modulation depth for diode laser absorption measurements in high-pressure gases

Tunable diode laser absorption measurements at high pressures by use of wavelength-modulation spectroscopy (WMS) require large modulation depths for optimum detection of molecular absorption spectra blended by collisional broadening or dense spacing of the rovibrational transitions. Diode lasers have a large and nonlinear intensity modulation when the wavelength is modulated over a large range by injection-current tuning. In addition to this intensity modulation, other laser performance parameters are measured, including the phase shift between the frequency modulation and the intensity modulation. Following published theory, these parameters are incorporated into an improved model of the WMS signal. The influence of these nonideal laser effects is investigated by means of wavelength-scanned WMS measurements as a function of bath gas pressure on rovibrational transitions of water vapor near 1388 nm. Lock-in detection of the magnitude of the 2f signal is performed to remove the dependence on detection phase. We find good agreement between measurements and the improved model developed for the 2f component of the WMS signal. The effects of the nonideal performance parameters of commercial diode lasers are especially important away from the line center of discrete spectra, and these contributions become more pronounced for 2f signals with the large modulation depths needed for WMS at elevated pressures.     

Use of periodic-heating method for measurement of thermal activity coefficient of gases

A method of increasing the sensitivity of the circuit for measuring the thermal activity coefficient of gases by the periodic-heating method is proposed. The thermal activity of argon, carbon dioxide, and air at 1300°K was measured.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 3, pp. 466–471, March, 1979.     

Concurrent multiaxis differential optical absorption spectroscopy system for the measurement of tropospheric nitrogen dioxide

The development of a new concurrent multiaxis (CMAX) sky viewing spectrometer to monitor rapidly changing urban concentrations of nitrogen dioxide is detailed. The CMAX differential optical absorption spectroscopy (DOAS) technique involves simultaneous spectral imaging of the zenith and off-axis measurements of spatially resolved scattered sunlight. Trace-gas amounts are retrieved from the measured spectra using the established DOAS technique. The potential of the CMAX DOAS technique to derive information on rapidly changing concentrations and the spatial distribution of NO2 in an urban environment is demonstrated. Three example data sets are presented from measurements during 2004 of tropospheric NO2 over Leicester, UK (52.62 degrees N, 1.12 degrees W). The data demonstrate the current capabilities and future potential of the CMAX DOAS method in terms of the ability to measure real-time spatially disaggregated urban NO2.     

Sensitivity enhancement of laser absorption spectroscopy for atomic oxygen measurement in microwave air plasma

A high sensitive laser absorption spectroscopy system has been developed for the detection of atomic oxygen in a microwave plasma. Firstly, the sensitivity of this system was evaluated by ring-down time measurement. The effective absorbing pass length was extended up to 640 times as long as that of the conventional laser absorption spectroscopy. Then, the system was applied to the air plasma diagnostics. As a result, the absorption signal from the meta-stable atomic oxygen at 777.19 nm could be observed at the input enthalpy range from 0.93 MJ/kg to 467 MJ/kg. The detected minimum number density was 1.6 × 10¹¹ m⁻³ with temperature of 388 K, which correspond to the center fractional absorption of 1.4 × 10⁻²% in the LAS.     

Acousto-optic differential optical absorption spectroscopy for atmospheric measurement of nitrogen dioxide in Hong Kong

Measurement of the atmospheric concentration of nitrogen dioxide (NO(2)) pollutant was demonstrated by differential optical absorption spectroscopy (DOAS) using a visible acousto-optic tunable filter. In a traditional spectral scanning DOAS system for atmospheric concentration monitoring, a highly stable light source is required. When the light intensity fluctuates during scanning, the concentration retrieval will be inaccurate. In order to reduce the error due to intensity fluctuations, a modified DOAS system has been developed by introducing a broadband light intensity monitoring channel. Using the measured intensity of the broadband channel as the intensity of the light source, the spectrum can be de-biased and the residual intensity variation will primarily result from atmospheric extinction. In addition, by employing the lock-in detection technique, the background light interference is also removed in the modified DOAS system. The atmospheric NO(2) concentration measurement was performed at the campus of City University of Hong Kong, and the results were compared with the concentration reported from a nearby monitoring station in Sham Shui Po, operated by the Hong Kong Environmental Protection Department.