Clean air measures

SI I97I/I6I Clean Air (Measurement of Grit and Dust from Eurnaces) Regulations... 

Cyclone Pressure Drop. Typical cyclone pressure drops range from 250 to 2000 Pa. Most data are reported for clean air flowing through the cyclone and these data are conservative for design purposes. Many investigators have unsuccessfully attempted to relate pressure drops to inlet and oudet dimension ratios. Manufacturers caUbration curves or experimental measurements on cyclones of similar dimension should be used where possible. If a rehable experimental measurement is available, however, the pressure drop at other conditions can be estimated by first evaluating the constant i in equation 17. 

In the United States, the Clean Air Act of 1990 requires plants to reduce emissions of 189 toxic and carcinogenic substances such as chlorine, chloroform, and 2,3,7,8-TCDD (dioxin) by 90% over the 1990s. The U.S. Environmental Protection Agency is working to develop standards based on maximum achievable control technologies and the industry has invested bUHons of doUars in capital investments to retrofit or rebuUd plant equipment to meet these measures. 

The AeroSizer, manufactured by Amherst Process Instmments Inc. (Hadley, Massachusetts), is equipped with a special device called the AeroDisperser for ensuring efficient dispersal of the powders to be inspected. The disperser and the measurement instmment are shown schematically in Figure 13. The aerosol particles to be characterized are sucked into the inspection zone which operates at a partial vacuum. As the air leaves the nozzle at near sonic velocities, the particles in the stream are accelerated across an inspection zone where they cross two laser beams. The time of flight between the two laser beams is used to deduce the size of the particles. The instmment is caUbrated with latex particles of known size. A stream of clean air confines the aerosol stream to the measurement zone. This technique is known as hydrodynamic focusing. A computer correlation estabUshes which peak in the second laser inspection matches the initiation of action from the first laser beam. The equipment can measure particles at a rate of 10,000/s. The output from the AeroSizer can either be displayed as a number count or a volume percentage count. 

Glean Air Act as Amended in 1990. The Clean Air Act Amendments of 1990 represent a mote recent effort by the U.S. Congress to address clean air concerns. The first Clean Air Act, passed ia 1967, provided authority to estabUsh air quaUty standards. Further legislation passed ia 1970, 1974, and 1977 extended and modified the original act. The seven tides of the 1990 Act not only extended previous measures, but also broke new conceptual ground. 

For combustible dusts, the explosibility limits do not have the same meaning as with flammable gases and flammable vapors, owing to the interaction between dust layers and suspended dust. This protective measure can, for example, be used when dust deposits are avoided in operating areas or in the air stream of clean air lines after filter installations WTiere in normal operation the lower explosibility limit is not reached. However, dust deposits must be anticipated with time. When these dust deposits are whirled up in the air, an explosion hazard can arise. Such a hazard can be avoided by regular cleaning. The dust can be extracted directly at its point of origin by suitable ventilation measures. 

Compare visibility measurements at a nearby airport with those of particle-free clean air. 

The results of this study demonstrated that the rate of oxygen transfer across a clean air-water interface was diffusion-controlled on the time scale of SECM measurements. The rate of this transfer process was, however, significantly reduced with increasing compression of a 1-octadecanol monolayer. Figure 28 illustrates this point, showing approach curves for O2 reduction recorded with the monolayer at different surface pressures. The transfer rate was found to depend on the accessible free area of the interface, as described by the following equation ... 

Excretion of hydrogen sulfide was documented after dermal exposure in rabbits. Trunk fiir of rabbits was clipped and left intact or abraded for exposure to hydrogen sulfide gas (unknown concentrations) for 1.5-2 hours the animals then breathed clean air (Laug and Draize 1942). Evidence for the excretion of hydrogen sulfide by the rabbits was a sulfide reaction of the expired air with lead acetate paper (Laug and Draize 1942). Sulfides in the expired air were noted in one rabbit with intact skin after 7 minutes of exposure. This study was limited by the lack of measurement of exposure concentrations and the small number of animals used. 

Highly toxic air pollutants fall under Section 112 of the Clean Air Act. Unlike criteria pollutants, these hazardous air pollutants must be controlled to protect the public health with an "ample margin of safety." Implied in this language is the belief in a discrete threshold of exposure below which no effects occur and from which a safety margin can be measured. Subsequent interpretations, however, indicated clearly that Congress did not equate safeguarding the public health with complete risk elimination. 

Fig. 3.34 LDA of the microarray signal patterns obtained in practical KAMINA tests to detect gaseous precursors of smoldering fires through overheated cable insulation. Prior to the LDA the measured resistances of the sensor segments were normalized to the median of all sensor segments and the number of variables was reduced by a Principal Component Analysis (PCA) to cutback the noise. Clear distinction is achieved between clean air...

Abstract. Model-measurement comparisons of HOx in extremely clean air ([NO]<3 ppt) are reported. Measurements were made during the second Southern Ocean Photochemistry Experiment (SOAPEX-2), held in austral summer 1999 at the Cape Grim Baseline Air Pollution Station in northwestern Tasmania, Australia. 

Measurement or estimation of health impacts under TSCA would be premature, since relatively little has been done to regulate new or existing chemicals that could result in health benefits. The principal exception to this generalization is the ban on aerosol uses of CFCs, whose chronic effects on human health derive from their environmental impact rather than direct biological toxicity. Compared with other environmental laws, such as the Clean Air Act, the regulatory accomplishments of TSCA are somewhat insubstantial. 

The required data generally are obtained by administering a measured dose of the candidate compound -- often isotopically labelled -- to the rat or mouse either by injection or per os. The animal is housed in a glass metabolism "cage" where it receives food, water, and clean air, and its urine, feces, and respired gases are collected and examined for the parent chemical and its metabolites. Eventual postmortem tissue analysis and calculation of material balance complete the measurements necessary to satisfy the above purposes of metabolism and pharmacokinetic experiments. While in vitro biochemical studies are important adjuncts, it is also apparent that only experiments with intact, healthy, living animals will suffice to meet EPA criteria. 

The results from total odour strength measurements of different chemical scrubbers, show odour reduction efficiencies between 95 per cent and 98 per cent. ED50 of the cleaned air has been found to be between 50 and 100, and the air has been characterized as free from sewage odours, but it smells like chemicals . It seems as if a chemical sembber always gives this scrubber odour . 

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