Airborne contamination protection against

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. 

Application of a protective overcoat to seal off airborne contaminants was also a popular approach initially. Although many polymers, lipophilic and hydrophilic, have been evaluated as a topcoat, water-soluble poly[ (meth)acryhc acid] is most commonly employed, which can be cast from a water solution without interfacial mixing with the resist layer and can be removed during aqueous base development. However, it has been reported that a poly(acrylic acid) overcoat allows diffusion of water, which reportedly contaminates a chemical amplification resist [211]. Poly(cx-methylstyrene) has been recommended as a good barrier against both airborne base and water [211]. 

Self-contained breathing apparatus (SCBA) Atmosphere-supplying Highest level of protection against airborne contaminants and oxygen deficiency. Highest level of protection under strenuous work conditions... 

In addition, depending on the type of chemicals and type of exposure, the respiratory tract should also be protected against inhalation of airborne contaminants, which can be in the form of particles, vapors or gases. Also, hearing protectors should not be forgotten. The need to use hearing protectors starts when the noise level, in spite of engineering control measures, exceeds the national limit value, which is 90 or 85 dB in many countries (Korhonen 1997). 

Probably the least understood piece of safety equipment is the respirator. Although dust masks may protect workers against many airborne particulates, these offer little or no protection against volatile chemicals. Respirators should be considered for use only by trained and certified employees, only under special circumstances, and only after all other controls of airborne contaminants have been implemented. In the laboratory, exhaust fans and fume hoods represent the first line of defense to contain and/or exhaust volatile hazardous materials. Without appropriate training, certification, medical approval, and careful fitting to the user s face, the use of respirators may, by itself, pose a significant health hazard. 

Service air is supplied at outlets throughout the plant to power air-operated tools and is used as a motive force for air-powered pumps. The service air subsystem is also utilized as a supply source for breathing air. Individually packaged air purification equipment is used to produce breathing quality air for protection against airborne contamination. 

Handling and Disposal of Chemicals in Laboratories Flammability of Chemical Substances Threshold Limits for Airborne Contaminants Octanol-Water Partition Coefficients Protection Against Ionizing Radiation Annual Limits on Intakes of Radionuclides Chemical Carcinogens... 

For many agents there is no acceptable, safe level of exposure. For example, only complete protection of the eyes against acid splashes, or the skin from contact with caustic liquids, is tolerable. However, for many airborne contaminants, the occupational exposure limit (OEL) or some fraction of it is usually specified as the acceptable level. 

Transmission of an organism or biotoxin can occur by various mechanisms, including droplet spread, direct physical contact or airborne spread. Mode of exposure will vary independently of the mechanism of transmission. For example, exposure from droplet spread of a viral agent may be inhaled from the atmosphere directly, or occur by physical contact with surface contamination and later oral ingestion. In terms of public health risk, agents that are reliably transmitted by airborne spread are fhe most dangerous, and most difficult to protect against. 

Any product that can be contaminated by airborne bacteria must be protected against them. In the case of foods, beverages and chemicals produced by fermentation, ingress of bacteria would cause serious defects in the products, if not their complete rejection. 

Topcoats also provide a protective function against airborne molecular contaminants such as amines. Figure 13.53 shows PEB delay stabilty of up to 15 minutes obtained on a resist film protected with a topcoat. Following the indicated PEB delay times, the resist film was postexposure baked and developed. Even after 15 minutes, the CD values of the 80-nm and 90-nm lines/space features remained remarkably stable. This is considerably better performance than that achieved when topcoat is not used. 

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