Contaminant, definition

Before selecting or sizing a specific control device, a careful evaluation of all aspects of the process and contaminants must be made. Improper terminology can lead to poor design and/or operation of any type of device. A list of contaminant definitions in accordance with the USA Standards Institute includes the following. 

A definitive method is one which establishes the accuracy and precision for all other methodologies. It is also operationally defined as one where all principal variables are connected by hard evidence to the absolute mass of the substance (Pb in this case) with an extremely high level of confidence. Given the cost, extreme demands on laboratory performance in terms of steps and freedom from Pb contamination, definitive procedures are confined... 

Thermal treatment is used to destroy, break down, or aid in the desorption of contaminants in gases, vapors, Hquids, sludges, and soHds. There are a variety of thermal processes that destroy contaminants, most of which are classified as incineration. Incineration HteraHy means to become ash (from Medieval Latin, incinerare in or into ashes). With respect to the incineration of hazardous wastes regulated in the United States, however, there is a strict legal definition of what constitutes an incinerator. The Resource Conservation and Recovery Act (RCRA) definition of incinerator at 40 CFR 260.10 is... 

Thermoanalytical methods (tga, dta) often enable definite identification of the type of asbestos fibers (Fig. 7). For example, the strong exotherm observed with chrysotile at 830°C can be used as a routine indicator for determining the chrysotile content of talc (4,10). Thermal methods are also usefiil for determining certain mineral contaminants of asbestos fibers, for example bmcite and calcite in chrysotile. 

In both these continuous processes medium to high energy disperse dyes should be used to avoid the risk of dye subliming to contaminate the atmosphere of the fixation unit and then staining the print by vapor-phase dyeing, or to produce a loss of definition of the printed mark due to diffusion from the appHed thickened paste. 

Waste minimization generally considers all of the methods in the EPA hierarchy (except for disposal) appropriate to reduce the volume or quantity of waste requiring dispos (i.e., source reduction). The definition oi source reduction as applied in the Pollution Prevention Act, however, is any practice that reduces the amount of any hazardous substance, pollutant, or contaminant entering any waste stream... 

Control of metalloid content in natural objects, foodstuff and pharmaceuticals is an important task for modern analytical chemistry. Determination of elements such as Arsenic is necessary for evaluation of object toxicity, since their content in environment may exceed MCL (maximum contaminant level), posing hazard to human health. Elements such as Selenium in definite doses are healthy, but in greater quantities they produce toxic effect. 

Establishing the physical and analytical boundaries for a QRA is also a difficult task. Even though you will provide input, the scope definition will largely be made by the QRA project team. Defining the physical boundaries is relatively straightforward, but it does force the QRA team to explicitly identify and account for interfaces that may significantly affect the QRA results. Eor example, analysts often treat a connection to a power supply (e.g., a plug) or a feed source as a physical boundary yet, loss of power or contamination of the feed must be considered in the QRA model. 

Cleanliness of the fuel must be monitored if the fuel is naturally dirty or can pick up contaminants during transportation. The nature of the contaminants depends on the particular fuel. The definition of cleanliness here concerns particulates that can be strained out and is not concerned with soluble contaminants. These contaminants can cause damage or fouling in the fuel system and result in poor combustion. 

The most useful application of ISS is in the detection and identification of sur-fece contamination, which is one of the major causes of product failures and problems in product development. The surface composition of a solid material is almost always different than its bulk. Therefore, surface chemistry is usually the study of unknown surfaces of solid materials. To better understand the concept of surface analysis, which is used very loosely among many scientists, we must first establish a definition for that term. This is particularly Important when considering ISS... 

Threshold lamit Value - The term refers to toxicity by inhalation. The abbreviation used is TLV. The TLV is usually expressed in units of parts per million (ppm) - i.e., the parts of vapor (gas) per million parts of contaminated air by volume at 25 °C (77°F) and atmospheric pressure. For chemicals that form a fine mist or dust, the concentration is given in milligrams per cubic meter (mg/m ). The TLV is defined as the concentration of the chemical in air that can be breathed for five consecutive eight-hour workdays (i.e., 40 hours per week) by most people without suffering adverse health effiects. This is the definition given by the American Conference of Governmental Industrial Hygienists. 

As mentioned above, the traditional definition of ventilation efficiency or, in approved terms, contaminant removal effectiveness, is the ratio between contaminant concentration in the exhaust air and the concentration at a point in the occupied space, i.e.,... 

Local ventilation is used to diminish or, preferably, to prevent exposure to contaminants (including heat). This includes protection of persons, products, or animals from hazardous and/or nuisance contaminants. This task is not specific for local ventilation and different definitions exist. One is the following ... 

FIGURE 10.6 Definition of capture efficiency, a, M = contaminant source rate, m = contaminant transport (directly) into the exhaust hood, a — m/M. 

One of the commonly used ventilation parameters is ventilation effectiveness, and it shows how certain regions in the room are influenced by contaminant sources introduced into the room. Three definitions of ventilation effectiveness are often used, namely, the ventilation effectiveness in the occupied zone the local ventilation index and the mean ventilation effectiveness They are defined as... 

Considered are mass conservation of air and species (contaminants and humidity). Momentum equations are not considered on a global scale but have been used in some cases for the definition of the airflow-pressure relation of the individual links. Heat fluxes and thus energy conservation equations are not considered. 

For iridium the position is reversed. This time it is the black dioxide, Ir02, with the rutile structure (p. 961), which is the only definitely established oxide. It is obtained by heating the metal in oxygen or by dehydrating the precipitate produced when alkali is added to an aqueous solution of [IrCl6] . Contamination either by unreacted metal or by alkali is, however, difficult to avoid. The other oxide, Ir203, is said to be... 

Effluent-treatment plants fail most commonly because the design is based on an inadequate or faulty definition of the effluent problem. In an existing works it may take months of painstaking research to establish the true patterns of flow and contamination. Predicting these for a new project can be extremely difficult, and serious mistakes are common. 

Contamination by flies may occur directly in a factory, especially if material is allowed to stand unprotected for long periods while being held for processing. Failure to dispose of refuse promptly, particularly outside the plant, frequently creates ideal breeding and feeding places for these pests. Under such circumstances, parts of the adult vinegar fly, its larvae, or eggs, when found in the comminuted product, provide definite evidence of careless and insanitary operations. 

Early 2005, Leadbeater s team reported that the previously claimed tran-sition-metal-free Suzuki-type protocol was definitely palladium-catalyzed [ 53 ]. Palladium contaminants down to the level of 50 ppb found in commercially available sodium carbonate were responsible for the generation of the biaryl. For good product yields in a short reaction time under microwave irradiation, a loading of 1 ppm Pd was required. 

Agricultural crops, effect of acidification, 52 Agricultural productivity, biocides-net productivity relationship, 307-308 Agricultural technologies, changes, 311,313 Airborne contaminants, description, 135 Airborne pollutant, definition, 135 Air pollutants, classifications, 66 Air pollution effects, 166,167r scope, 21-22 sources, 165-166 state, 4... 

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