Toxic atmospheres monitoring

Toxic atmospheres monitoring, 308 sources, 67, 229 Toxic chemicals ... 

Kimbell CL. 1982. Atmospheric monitoring for hydrogen sulfide by photorateometric analysis. Toxic Materials in the Atmosphere ASTM STP 786 60-69. 

J. W. Scientific Corporation, Product literature and catalog, Folsom, CA 1995. Kimbell, C. L., Atmospheric monitoring for hydrogen sulfide by photorateometric analysis, in Toxic Materials in the Atmosphere Sampling and Analysis, ASTM special technical publication 786, American Society for Testing and Materials, Philadelphia, PA, 1982, 60. 

The major topics related to managing hazardous air pollutants are addressed in this book, such as national and International approaches to regulating air toxics, research activities, stack and atmospheric monitoring, and the fate of toxics emissions in the atmosphere. 

Electrochemical H2S sensors are among the most dependable, stable and reliable type of gas detecting sensors available. However, no sensor can detect gas unless it is used. The only way of being sure that toxic contaminants are not present in dangerous concentrations is to look for them with an atmospheric monitor designed for their detection, and take action at the appropriate concentration. 

The widest application of PTR-MS is in the field of atmospheric monitoring. In air, VOCs originate from diverse sources but primarily from biogenic origin. Many VOCs have effects on the sources and sinks of ozone, aerosol formation, and climate change. In addition, some VOCs are also toxic to human beings [34], so it is important to monitor their concentrations in wider environments. Nowadays, PTR-MS has been used to detect VOCs from plants, forest, and human activities. 

Other oxygen and toxic-gas monitors are based on fuel-cell technology, the current being measured between a porous fuel cell working electrode and a counter-electrode. The problems and successes of this approach are very similar to those of the membrane cells described above. An interesting variation has been used to manufacture a breathalyser which has been accepted by several national and state police forces. It is based on two Pt-catalysed porous fuel cell electrodes (Fig. 12.14). The cathode is open to the atmosphere so that the reduction of oxygen can occur when a suitable fuel is present at the anode and to... 

Hundreds of chemical species are present in urban atmospheres. The gaseous air pollutants most commonly monitored are CO, O3, NO2, SO2, and nonmethane volatile organic compounds (NMVOCs), Measurement of specific hydrocarbon compounds is becoming routine in the United States for two reasons (1) their potential role as air toxics and (2) the need for detailed hydrocarbon data for control of urban ozone concentrations. Hydrochloric acid (HCl), ammonia (NH3), and hydrogen fluoride (HF) are occasionally measured. Calibration standards and procedures are available for all of these analytic techniques, ensuring the quality of the analytical results... 

As mentioned earlier, toxic releases may consist of continuous releases or instantaneous emissions. Continuous releases usually involve low levels of to.xic emissions, wiiich are regularly monitored and/or controlled. Such releases include conlinuous slack emissions and open or aerated chemical processes in wliich certain volatile compounds are allowed to be stripped off into the atmosphere tliroiigh aeration or agitation. Mathematical models for these releases to tlie enviroiuncnt are covered in detail in Part III. 

Thermal desorption is a technique that involves the pre-concentration of substances prior to chromatography. For example, it enables the build-up of volatile materials such as toxic solvent vapours in an industrial or laboratory environment to be monitored. The vapours are allowed to pass through a small tube containing an absorbent such as Tenax or Poropak by atmospheric diffusion for a prescribed period of time. The tube is subsequently connected to the injection port of the chromatograph and purged with carrier gas whilst being rapidly heated. This causes any previously adsorbed substance to be thermally desorbed and swept onto the column in a narrow band to be separated in the normal way. 

The odor threshold, 0.58 ppm to 5.0 ppm (Amoore and Hautala 1983 Ruth 1986) is low compared with irritant or toxic concentrations. No acute exposures were located resulting in mild effects in humans. Three monitoring studies, involving no symptoms to mild symptoms during chronic occupational exposures of adult males, are relevant to development of AEGL-1 values. The symptoms and blood concentrations of cyanide in the monitoring study of Chandra et al. (1980) indicate that the workers may have been exposed at higher atmospheric concentrations than those reported. 

Data Adequacy Although human data are limited to primarily occupational monitoring studies, the data base on animal studies is good. The test atmosphere in the key study was supplied via a face mask to the restrained test subjects restrained animals have been shown to be more sensitive than unrestrained animals to inhaled toxicants. Relative species sensitivity to inhaled HCN may be related to breathing rate. Compared to rodents, the slower breathing rate of humans and monkeys may make them less sensitive to the effects of HCN. 

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