HEPA filter treatment

Other applications of filters include sterilization of venting or displacement air in tissue and microbiological culture (carbon filters and hydrophobic membrane filters) decontamination of air in mechanical ventilators (glass fibre filters) treatment of exhausted air ftom microbiological safety cabinets (HEPA filters) and the clarification and sterilization of medical gases (glass wool depth filters and hydrophobic membrane filters). 

PET bottles are made from resin chips in a two-stage process (even if made on one machine). A preform is injection moulded and is sterile when formed this is then blown into the final shape. If the machine is enclosed in an HEPA-filtered environment and the bottles blown with sterile air, the machine produces a sterile bottle. The bottle can be transferred to the filler within an enclosed sterile ah conveyor and filled without further treatment, thus eliminating the need for rinsing and chemical treatment. Carbonated products can be filled if the carbon dioxide is sterilised. 

In terms of decontamination, the ceric leaching appears adequate for HEPA filters. The experimental studies (5>15 >l6) have achieved 99 99% dissolution of the most refractory of the tetravalent actinides. However, the leaching of the incinerator ashes (5l>16 ) has been less successful, since as much as 5 of the alpha activity initially in this waste does not dissolve with ceric treatment alone. However, this last 5 may be recovered by dissolving the ash residuum entirely with fluoride. (This 5 loss would represent about 0.05 of the actinide feed to the main plant.)... 

Reisman R, Mauriello R Davis G, et al. A double-blind study of the effectiveness of a high efficiency particulate air (HEPA) filter in the treatment of patients with perennial allergic rhinitis and asthma J Allergy CUn Immunol 1990 85 1050-1057. 

Offgas treatment is extensive and involves use of sintered metal filters, quench systems, venturi scrubbers, a condenser, a mist eliminator, an offgas heater, parallel HEPA filters, a carbon filter for radioactive iodine removal, a baghouse, and a selective catalytic reduction unit a packed tower scrubber system is used as a backup. 

Specific treatment combinations can be designed to match airborne contaminants from the physical or chemical operations, the type of sample (solid, liquid, gas), and the quantity that is processed. For example, sample preparation rooms where soil and vegetation are dried, ashed, ground and sieved require particle filter combinations but not charcoal beds and scrubbers. For treating laboratory air, the multiple stage filter system should be based on the expected maximum radionuclide concentration and airborne fraction of the processed samples. Typical combinations include pre-filters, HEPA filters and charcoal beds. 

Concerning radiation protection outside the plant, a barrier concept with progressive rates of vacuum from inside (e.g., glove boxes) to the outer atmosphere in connection with the ventilation system and treatment of off-gas by HEPA filters will achieve protection of the population. Emission of airborne radioactivity is monitored and the radioactivity of liquid effluents is controlled. 

Wet Scrubber Cell. The wet scrubber forms the second part of the secondary off-gas treatment. It removes active volatile contaminants from the off-gas stream, together with some of the remaining particulates before filtration. The wet scrubber operates continuously. Filter Cell. The filter cell contains banks of HEPA filters, associated ductwork, and ancillary equipment. The function of the filter cell is to filter the off-gas from the vessel and cell ventilation systems before the off-gas is discharged to the environment. 

Hoods used for work with radioactive sources or materials should be designed so that they can be decontaminated completely on a regular basis. A usual feature is a one-piece, stainless steel, welded hner with smooth, curved comers, which can be cleaned easily and completely. The superstructure of radioisotope hoods is usually made stronger than that of a conventional hood in order to support lead bricks and other shielding that may be required in the hood. Special treatment of the exhaust from radioisotope hoods may be required by government agencies to prevent the release of radioactive mataial into the environment. This usually involves the use of high-efficiency particulate air (HEPA) filters (see section 8.C.8.4). 

The gaseous waste treatment system prowdes storage of radioactive effluent until it decays down to a value allowable for discharge to the environment through the HEPA filter and iodine filter into the plant stack. 

Filters used during offgas treatment (carbon, HEPA, etc.). 

The offgas treatment systems and agent filter area (AFA) have filtering systems that will produce waste. These include particulate filter w aste, iron sponge absorber waste, prefilters, and high-efficiency particulate air (HEPA) and activated carbon filters. Activated carbon is used as filter medium in... 

A basic clean-room system will normally be connected to a factory s centfal air treatment system, with HEPA/ULPA filtration as close to the clean room as possible (Eigure 6.12). The figure shows two different clean room arrangements connected to the air-conditioning system s manifold, each with high efficiency filters as near as possible to the air outlet into the room concerned. The very clean inlet air is optimally mixed with the room air so that the desired degree of purity is achieved. 

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