High efficiency particle air

The number of air changes should generally be higher than 20 per hour in a room with good air flow pattern and appropriate high efficiency particle air (HEPA) filters. 

The number of air changes should generally be higher than 20 per hour in a room with good air flow pattern and appropriate high efficiency particle air (HEPA) filters. Laminar air-flow work station. Systems should provide homogeneous air speed of 0.3M/s vertical and 0.45 M/s horizontal flow. Only reliable when a large number of air samples is taken. Source Ref. 10. >>. - ... 

It is beyond the scope of this section to describe the lay-out of clean laboratory facilities in detail see the excellent reviews by Whyte (1991) and Liebennan (1992). TTie basic concept behind the operation of such rooms is that they are under positive pressure and that the air is first drawn through one or two pre-filters, and then forced through a high efficiency particle air (HEPA) filter which removes typically > 99.97 % of particles S 0.3 nm in diameter. 

High efficiency particle air (HEPA) filter (contamination control) See Mechanical filter. 

HEPA High efficiency particle air (see also ULPA)... 

The purpose of open unidirectional airflow benches is to protect products from particulate contaminants by creating a controlled environment. These benches are used, for example, in electronic, biological, pharmaceutical, and food industries. It should be mentioned that within pharmaceutical production, aseptic sterile processes must be carried out in a Class 100 environment (U.S. Federal Standard 209 E, Airborne Particulate Cleanliness Classes in Cleanrooms and Clean Zones). To avoid particle contamination in the bench, horizontal or vertical airflow with high-efficiency particulate air (HEPA)-filtered air is used. The air velocity is normally 0.4-0.5 ra s". Some examples of typical arrangements of open unidirectional airflow benches are shown in Fig. 10.51. 

Air filter A device that removes particulate matter from a gas flowing through it. These are classified as Absolute A high-efficiency particulate air filter that is at least 99.79% efficient in the removal of thermally generated mOnodisperse dioctylphthalate smoke particles with a diameter of 0.3 pm, also known as a HEPA filter. 

HEPA A high-efficiency particulate air filter designed to deal with particles below 1 pm with efficiencies... 

Efficiency testing of high-efficiency partieulate air (HEPA) filters used for the supply of sterile air to aseptie workplaces (Chapter 22) is normally achieved by the generation upstream of dioetylphthalate (DOP) or sodium ehloride particles of known dimension, followed by deteetion in downstream filtered air. Retention efficiency is reeorded as the percentage of partieles removed under defined test conditions. Microbiological tests are not normally performed. 

High-efficiency particulate air filters can remove lightweight particles such as pollens, mold spores, and cat allergen, thereby reducing allergic respiratory symptoms. 

Filter A High-Efficiency Particulate Air (HEPA) filter is at least 99.97 percent efficient in removing particles with a diameter of 0.3 microns. 

Shielding Rule 2 Heat the air of a sealed building to create positive pressure and prevent the infiltration of contaminants. Always use recirculated air or air purified by a high-efficiency particle arrestor (HEPA) filter. If this is not possible, turn the heating and air conditioning system off. 

Table 9-1 lists design features of the exposure chambers in the United States that have air-cleaning equipment. The facility at the University of Maryland Hospital, Baltimore, has a chamber with activated-charcoal and high-efficiency particle filters and controlled temperature and humidity. St. Vincent s Hospital and New York University, New York City, each have a clean-room facility. The University of Pennsylvania Hospital, Philadelphia, has a self-contained, reinforced-concrete... 

The largest volume of radioactive waste is made up of the ventilation air from processes, plants, and laboratories. However, the quantity of radioactivity is relatively low. It generally occurs in a particulate form readily removed by dry filters. A special class of paper filters developed for this purpose (HEPA or High Efficiency Particulate Air) removes 99.97 percent of 0.3-micron particles. These filters frequently are preceded by scrubbers, sorbers, and roughing filters to extend the life of the paper filter. 

Mechanical filtration systems are intended to limit the introduction of pollutants from outdoors to indoors. The efficiency of such systems generally depends on the filter properties and the aerodynamic properties of filtered particles [26]. The efficiency of filters varies from 5% to 40% for low-efficiency filters, such as dry media filters, panel and bag filters, from 60% to 90% for electrostatic precipitators to over 99% for high-efficiency particulate air filters. Not only the filters, but the whole heating, ventilation and air-conditioning system contributes to particle reduction, owing to particle losses on the cooling/heating coil and other parts of the system. The selection of a system depends on the type of indoor environment, outdoor and indoor sources, the demand on the level of reduction of pollutant concentrations and the cost associated with purchase, operation and maintenance of the system. 

Note The required degree of air cleanliness in most OSD manufacturing facilities can normally be achieved without the use of high-efficiency particulate air (HEPA) filters, provided the air is not recirculated. Many open product zones of OSD form facilities are capable of meeting ISO 14644-1 Class 8, at-rest condition, measured against particle sizes of 0.5 pm and 5 pm, but cleanliness may not be classified as such by manufacturers. 

An air filtration system removes aerosols, vapor, oil, and particles as small as 0.03 microns from cooling air that circulates under positive pressure within the system s protective shield, cleaning and cooling the camera, lens, and the achromatic relay lenses that carry the images of the flames from the lens to the camera. This self-purging, high-efficiency compressed air filter ensures trouble-free performance and a clear view of the furnace interior. The compressed air finally goes out the front end of the probe. 

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