Contaminants, airborne

Three approaches have been identified that reduce susceptibility of CA resists to airborne contamination. In the first, process engineering changes such as the addition of special activated carbon filters to the environmental chambers surrounding the exposure tools (76,79), overcoating the resist with a soluble protective film to isolate the resist from the environment (77,80,81), or modifications of the process flow to minimize the time interval between exposure and post-exposure bake have been shown to improve CA resist processibibty. 

Board on Toxicology and Environmental Health Ha2ards, National Research Council, Emergeny and Continuous Exposure Eimitsfor Selected Airborne Contaminants, Vol. 1, National Academy Press, Washiagton, D.C., Apr. 1984. 

The most common supported tubes are those with membranes cast in place (Fig. 17). These porous tubes are made of resin-impregnated fiber glass, sintered polyolefins, and similar materials. Typical inside diameters are ca 25 mm. The tubes are most often shrouded to aid in permeate collection and reduce airborne contamination. 

Foulants enter a cooling system with makeup water, airborne contamination, process leaks, and corrosion. Most potential foulants enter with makeup water as particulate matter, such as clay, sdt, and iron oxides. Insoluble aluminum and iron hydroxides enter a system from makeup water pretreatment operations. Some well waters contain high levels of soluble ferrous iron that is later oxidized to ferric iron by dissolved oxygen in the recirculating cooling water. Because it is insoluble, the ferric iron precipitates. The steel corrosion process is also a source of ferrous iron and, consequendy, contributes to fouling. 

Both iron and aluminum are particulady troublesome because of their abiUty to act as coagulants. Also, their soluble and insoluble hydroxide forms can each cause precipitation of some water treatment chemicals, such as orthophosphate. Airborne contaminants usually consist of clay and dirt particles but can include gases such as hydrogen sulfide, which forms insoluble precipitates with many metal ions. Process leaks introduce a variety of contaminants that accelerate deposition and corrosion. 

IDLH means immediately dangerous to life and health. This is a concentration at which immediate action is required. The exac4 effect on an individual depends on the individuals physical condition and susceptibility to the toxic agent involved. It is the maximum airborne contamination concentration from which one could escape within 30 min without any escape-impairing symptoms or irreversible health effects (developed by NIOSH). 

Constance, J. D. 1983. Controlling In-Plant Airborne Contaminants. Marcel Dekker, New York. 

ISA S71.04. 1986. Environmental Conditions for Process Measurement and Control Systems Airborne Contaminants. Instrument Society of America, Research Triangle Park, N.C. 

In the case of animals we are concerned primarily with a two-step process accumulation of airborne contaminants on or in vegetation or forage that serves as their feed and subsequent effects of the ingested herbage on animals. In addition to pollution-affected vegetation, carnivores (humans... 

DUST Solid particles generated by mechanical action, present as airborne contaminant (e.g. <75 pm in size). 

PARAOCCUPATIONAL EXPOSURE Exposufe of wofkers to an airborne contaminant from a nearby process or operation not forming part of their jobs. Also termed neighbourhood exposure . 

Use handling technique that avoids airborne contamination Mechanical handling... 

Process Associated problems Hazardous airborne contaminants liberated (in addition to tbe principal reagents)... 

British Occupational Hygiene Society (1988J Controlling Airborne Contaminants in the Workplace, Technical Guide No. 7, BOHS, Norwood, Science Reviews. 

In recent years, the use of solvent-borne adhesives has been seriously restricted. Solvents are, in general, volatile, flammable and toxic. Further, solvent may react with other airborne contaminants contributing to smog formation and workplace exposure. These arguments have limited the use of solvent-bome adhesives by different national and European regulations. Although solvent recovery systems and afterburners can be effectively attached to ventilation equipment, many factories are switching to the use of water-borne rubber adhesives, hot melts or 100% solids reactive systems, often at the expense of product performance or labour efficiency. 

Take photographs, as appropriate, and detailed notes concerning visible airborne contaminants, work practices, potential interferences, movements, and other conditions to assist in determining appropriate engineering controls. 

In exposures by inhalation of airborne materials, the dose is the concentration multiplied by the time (CT), and is roughly a constant for any given material and specified effect. The CT value can be used to provide a rough approximation of other combinations of concentration and time which would have about the same effect. Although this concept must be used very cautiously and cannot be applied at extreme conditions of either concentration or time, it is most important in setting limits for airborne contaminants and physical agents in respect to environmental exposures. The worker is exposed for various periods of time, day after day, to the... 

The TLVs, as recommended and published by the ACGIH, refer to concentrations of airborne contaminants or levels of physical agents, and represent the conditions to which it is believed nearly all workers may be repeatedly exposed day after day without adverse effects. TLVs are based on the results of animal experiments, limited human experiments, some industrial experience and, when possible, a combination of all three. 

The TLVs for airborne contaminants are based on the premise that although all chemical substances are toxic at some concentration for some period of time, a concentration exists for all substances from which no toxicity may be expected no matter how often the exposure is repeated. A similar premise holds for substances producing irritation, discomfort and nuisance. In using these limits, items such as excursion factors, ceiling values, "skin" notations, mixtures of substances, and inert material should be considered. These factors are discussed below. 

Airflow Systems, Inc Resource for the collection and filtration of dust, smoke, mist, fumes and other airborne contaminants generated during industrial and commercial manufacturing and processing applications. http., llwww.air, flowsvstems. com... 

Loose, fixed, surface, subsurface, or airborne contamination... 

The employer is required to identify hazardous airborne contaminants that employees may inhale and make a reasonable estimate of employee exposure in determining the appropriate respirator for employees to use. Oxygen-deficient atmospheres and those atmospheres that are not or cannot be estimated should be treated as IDLH environments. 

Generation of airborne contaminants from improper use of equipment (i.e., jet sprayers, vacuum cleaners) [2]... 

This chapter describes calculation models for building energy demand and air flow in and around industrial buildings. Special attention is paid to simulation of airborne contaminant control. 

However, assessing occupational exposure to airborne contaminants in a representative way is not an easy task and requires a good deal of professional judgment and reliance on a good methodology. There are many issues to be resolved, such as... 

Among the major potential hazards affecting working environment are chemical (airborne contaminants), biological, and physical hazards,. ir contaminants are commonly classified as either particulate contaminants or gas and vapor contaminants. Common particulate contaminants include dusts, fumes, mists, aerosols, and fibers. 

Airborne contaminant movement in the building depends upon the type of heat and contaminant sources, which can be classified as (1) buoyant (e.g., heat) sources, (2) nonbuoyant (diffusion) sources, and (d) dynamic sources.- With the first type of sources, contaminants move in the space primarily due to the heat energy as buoyant plumes over the heated surfaces. The second type of sources is characterized by cimtaminant diffusion in the room in all directions due to the concentration gradient in all directions (e.g., in the case of emission from painted surfaces). The emission rare in this case is significantly affected by the intensity of the ambient air turbulence and air velocity, dhe third type of sources is characterized by contaminant movement in the space with an air jet (e.g., linear jet over the tank with a push-pull ventilation), or particle flow (e.g., from a grinding wheel). In some cases, the above factors influencing contaminant distribution in the room are combined. 

A workbench makes use of a local air supply in conjunction with exhaust air to ensure good control of the contaminants generated on a bench process. The local exhaust removes the contaminants, while the local supply air protects the operator and/or the products against airborne contaminants. The local supply air improves the thermal environmental conditions by introducing cool dehumidified air in a hot environment. This ensures that the operator s thermal comfort is maintained in areas of high temperature, where full air conditioning of the entire workspace is nor economically feasible. 

Contaminant concentrations Dispersal of airborne contaminants such as odors, fumes, smoke, VOCs, etc. transported by these airflows and transformed by a variety of processes including chemical and radiochemical transformation, adsorption, desorption to building materials, filtration, and deposition to surfaces evolution of contaminant concentrations in the individual zones air quality checks in terms of CO2 levels cross-contamination evaluation of zones air quality evaluations in relation to perception as well as health. Methods ate also applicable to smoke control design. 

Personal exposure Predictions of exposure of occupants to airborne contaminants for risk assessment, inhaled doses, or time-integrated concentration values. 

Air cleaner A device that removes airborne contaminants from air. 

Air cleaning equipment Equipment that removes airborne contaminants, either... 

Air-purifying respirator A respirator that removes airborne contaminants, such as particulates, gases, vapors and fumes, from ambient air through filtration, absorption, adsorption, or chemical reactions on the media contained in the cartridge or filter. 

Detector tube A direct method for identifying airborne contaminants, also known as length-of-stain tube. It is a convenient tool for detecting and quantifying contaminants in field or emergency situations. 

Immediately dangerous to life and health (IDLH) A condition that poses a threat of exposure to airborne contamination likely to cause death or immediate or delayed permanent adverse health effects, or that prevents escape. 

All finishes should be selected to be resilient to expected average and worst-case environmental exposure such as high/low humidity or temperature, airborne contaminants, vibration, possible aggressive liquid spillages, cleanliness/hygiene requirements, etc. 

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