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BACKGROUND Surgical helmet systems commonly are stand-alone systems with a single fan blowing air into the suit, creating positive pressure that blows particles out through areas of low resistance, possibly contaminating surgical attire and the surgical field. Two-fan systems were developed more recently to release spent air, also theoretically lowering pressure in the suit and decreasing the aforementioned risk of particle contamination. To our knowledge no study to date has measured the potential differences in gown particle contamination to support this hypothesis. QUESTIONS/PURPOSES We compared a commonly used single-fan system versus a two-fan system and asked: (1) Which fan system results in less gown particle contamination? (2) Are there differences between the systems in the location of contamination? METHODS Using an existing experimental study model, two surgeons performed five 30-minute TKA simulations comparing a single-fan to a double-fan helmet system after applying fluorescent powder to the hands, axillae, and chest. Both are two-piece hood and gown systems. The single-fan sits on top of the helmet blowing air into the suit; the double-fan system has a second fan positioned at the rear blowing out spent air. Ultraviolet light-enhanced photographs were subsequently obtained of the flexor and extensor surfaces of the arms, axillary areas, and front and back of the chest. We chose these locations because they all contain either a seam or an overlap between gown and hood or gloves through which particles can escape. The images were scored for contamination on a scale of 1 (zero specks) to 4 (> 100 specks) by three independent observers. Interobserver correlation was assessed through Spearman's test yielding 0.91 (95% CI 0.86 to 0.94; p < 0.0001), 0.81 (95% CI 0.73 to 0.87; p < 0.0001) and 0.87 (95% CI 0.80 to 0.91; p < 0.0001) between observers 1 and 2, observers 1 and 3, and observers 2 and 3, rendering the used scale reliable. Results of the observers were averaged and compared using the Mann-Whitney U test. RESULTS There was no difference in overall gown particle contamination between the systems (overall single-fan median contamination score 2.5 of 4 [interquartile range Q1-Q3 0-3.42] versus double fan 1 out of 4 (Q1-Q3 0-3); p = 0.082), but all tests showed there was contamination at the gown-glove interface. In general, there were few differences between the two systems in terms of location of the contamination; however, when comparing only the axillary regions, we found that the single-fan group (median score 3.67 [Q1-Q3 3-4]) showed more contamination than the double-fan group (2.33 [Q1-Q3 0-3.08]); p = 0.01. CONCLUSION We found no difference in gown particle contamination between a single-fan and a double-fan helmet design. However, we note that contamination was present in all tests with both systems, so surgeons should not assume that these systems provide a contamination-free environment. CLINICAL RELEVANCE When using such helmets, the surgeon should not place items close to the axillary region because the seam of the gown may have low resistance to particle contamination. Gown designs could be improved by creating better seals, especially at the arm-body seam.

Silica substrates coated with organic thin films were exposed to stainless steel and silica micro-particles to determine the effectiveness in preventing particle contamination and cleaning efficiency by air flows. Three specially designed monolayers coatings were developed and tested. Laser induced damage tests were conducted to confirm that the coatings do not affect the LIDT values. The results suggest that although the accumulation of particles is not significantly affected, the coated substrates exhibit significantly improved cleaning efficiency with air flow. A size distribution analysis was conducted to study the adsorption and cleaning efficiency of particles of different sizes.

Oil contamination resulting from externally ingested particles is one of the major causes of journal bearing failure in industrial machinery. The present study has been carried out to assess the case of externally ingested particle contaminants in a journal bearing lubrication using acoustic emission (AE) and vibration monitoring techniques. Besides quantitative evaluation, the features of AE and vibration spectra have been classified and key parameters for condition monitoring deduced. Furthermore, cases involving different particles sizes and concentrations have been exhaustively examined and illustrated; and the capability of these two methods described in terms of detectability.

The presence of contaminants in polyethylene terephthalate (PET) bottles and derived materials from the various steps in the recycling loop is studied. Based on these measurements, a model is proposed to generically describe the accumulation of these contaminants within closed‐loop recycling schemes for PET bottles. The measured levels of particle contamination and chlorine content of PET bottles, pellets, and intermediate recycling products are used to derive the modelling parameters. Previously determined relations between these measured parameters and critical bottle properties are used to model the effect of the accumulation of the contaminants on the bottle properties. The measurements reveal that the type of collection system influences the accumulation of contaminants in PET bottles greatly. PET bottles in mono‐collection systems accumulate less contaminants than PET bottles in co‐collection systems do. Therefore, PET bottles within recycling schemes using mono‐collection systems can contain more recycled content than those from co‐collection systems, without exceeding acceptation limits on critical bottle properties such as haziness, yellowing, and migration.

Nowadays, power transformer is most crucial electrical equipment in a power system. Researcher has been emphasized a lot of researches on natural ester oils to replace mineral oil that act as insulating liquid in power transformer. In this paper, an effort has been made to investigate corn oil (CO) as alternate liquid insulation to mineral oil (MO). Copper are used as particles contamination in this project. There are 12 oil samples has been prepared. Two samples which are pure MO and pure CO for before aging and 10 oil samples which are five samples of pure MO and five samples of pure CO for after aging. The particles contamination that used in this experiment which is copper with different size of length was added in each sample for after aging. The length sizes of copper were 5cm, 10cm, 15 cm, 20cm, 25cm and 30cm. In this report, the investigation of AC breakdown voltage involved two stages which are before aging and after aging. For before aging, two oil samples are only conducting AC breakdown voltage. Moreover, for after aging another 10 sample has been heated in the oven with temperature 115°C at 96 hours in order to investigate the effect of particle contamination in the transformer oil. From the experiment result that conducted, pure CO higher value of AC breakdown voltage than pure MO for before aging. But, after aging process, the value of pure MO with difference size of copper is higher than pure CO. It show that CO is good oil insulator to replaced MO for the future, but for use in long term, MO still the best insulator because has higher AC breakdown voltage than CO after aging process.

With the introduction of the NXE:3400B scanner, ASML has brought EUV to High-Volume Manufacturing (HVM). In this context, ASML is pursuing a dual-path approach towards zero reticle defectivity: EUV-compatible pellicle or zero particles towards reticle by advanced particle contamination control. This paper will focus on the latter approach of advanced particle contamination control and will show that we are able to reduce particle contamination towards reticle to a level that is compatible with HVM requirements for sub-10nm node lithography.

Heat transfer fluid (HTF) cleanliness is critical to the effectiveness and safety of an HTF system. Routine monitoring of HTF condition is a critical part of ongoing HTF system maintenance. However, the condition of any fluid introduced into a HTF system needs to be monitored closely to ensure that foreign contaminants are not introduced. Such contaminants act to accelerate the ageing of an HTF once in operation. The current research concerns the flushing and cleaning protocol that is used to remove foreign contaminants during the building of a new HTF system. The current study was performed in Scandinavia for a client building a new HTF system that had a capacity of 100 metric tons. The system was flushed with Globaltherm® C1 was used to flush and clean the system prior to filling with a synthetic HTF. The value of the protocol was assessed in terms of its ability to remove contaminants – water, environmental and system build contaminants. The protocol involved the use of a fine filter (15 microns pores) and laboratory analysis to assess cleanliness of the fluid. The results from nineteen fluid samples are presented herein. Results show the presence of water and particle contaminants (4, 6 and 14 microns in size) including silicon, aluminium, iron, calcium and zinc. The flushing and cleaning fluid works by suspending particles in solution and these are subsequently drained from the HTF system. The detection of particles in the fluid demonstrates that the flushing and cleaning fluid and the protocol are effective in removing finer particles from a system. Further analysis assessed the relationship between water and particle contaminants. Results showed a positive association between water and the presence of larger particles (i.e., 14 microns). No association was found between water and smaller particles (4 and 6 microns). These data highlight the value of monitoring both water and particle contamination, and that water may be a substitute method to measuring particles directly. The presence of water in a fluid can be observed and detected onsite, so this may be an early sign of other contaminants present in a newly build HTF system. To conclude, the flushing and cleaning protocol described herein is effective in the removal of contaminants during a HTF system build. This protocol has been shown to be effective by subsequent laboratory analysis. The presence of water may be an early sign of environmental contamination and the formation of rust.

Plastic particles are small micro and nano range materials internationally produced for industrial applications or as a result of the breakdown of larger plastics. The accumulation of plastic particles varies spatially and temporally, with locations, hydrodynamic conditions, environmental pressure, time, and anthropogenic factors accounting for the disparities in dispersal and distribution. The accelerating global release of plastic particles into the environment seems unending, with long-term consequences for water quality, biodiversity, biological conservation, and human health. In this paper, we review the formation, presence, and toxicity of plastic particles in water, land, and air. Plastic wastes and plastic particles are increasing in abundance every year with increased consumption and rise in the global population. These materials are easily transported over long distances and become ubiquitous in their distribution on land, water, and air with unknown and unproven ecological and human health risks. Notwithstanding the potential threats to ecological health, literary records of plastic particle contamination of environmental media in Africa are very scanty. Managing environmental waste plastics and plastic particles and ensuring effective intervention policies and practices requires an understanding of plastic particles sources, transport, and fate, through regional and international collaboration, and interdisciplinary research. In consideration of the potential threats of plastic particles to ecological functions and human health risks, we recommend specific regulation of microplastics in consumer products. The information contained in this paper adds to the growing body of knowledge in the study of micro- and nano-plastic particles worldwide but with particular reference to developing countries.

This chapter provides an overview of contamination that can be encountered during semiconductor device manufacturing. Contamination can have a detrimental impact on yield and reliability, but also on process control. In the conventional classification scheme, a distinction is made between particle contamination, metallic contamination, and airborne molecular contamination. For each of these contaminants, a brief overview is given of the sources of contamination and the mechanisms by which the contamination is deposited on the substrate surface. Also general properties and possible effects of the contamination are discussed. In addition, possible detrimental effects of contaminant removal and cleaning are reviewed.

For class II, type A2 biological safety cabinets (BSC), NSF/ANSI Standard 49 should be conformed in cabinet airflow velocity derivation, particle contamination, and aerodynamic flow properties. However, there exists a potential problem. It has been built that the cabinet air flow stabilize is influenced by the quantity of downflow of air and the height above the cabinet exhaust opening. Three air downflow quantities were compared as an operating apparatus was placed from 20 to 40 cm above the bench of the cabinet. The results show that the BSC air downflow velocity is a function of increased sampling height, displaying that containment is improvingly permitted over product protection as the sampling height decreases. This study investigated the concentration gradient of particles at various heights and downflow air quantity from the bench of the BSC. Experiment results indicate that performance near the bench was better than in the rest of the BSC. In terms of height, the best cleanliness was measured at a height of 10 cm over the bench; it reduced actually with add in height. The empirical curves accommodate, founded on the concentration gradient of particle created was elaborated for evaluating the particle concentration at different heights and downflow air quantity from the source of the bench of the BSC. The particle image velocimetry system applied for BSC airflow research to fix amount of airflow patterns and air distribution measurement and results of measurements show how obstructions can greatly influence the airflow and contaminant transportation in a BSC.

Background The original Charnley-type negative-pressure body exhaust suit reduced infection rates in randomized trials of total joint arthroplasty (TJA) decades ago. However, modern positive-pressure surgical helmet systems have not shown similar benefit, and several recent studies have raised the question of whether these gowning systems result in increased wound contamination and infections. The gown-glove interface may be one source of particle contamination.

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)., Organic dust and related microbial exposures are the main inducers of several respiratory symptoms. Occupational exposure to organic dust is very common and has been reported in diverse settings. In vitro tests using relevant cell cultures can be very useful for characterizing the toxicity of complex mixtures present in the air of occupational environments such as organic dust. In this study, the cell viability and the inflammatory response, as measured by the production of pro-inflammatory cytokines tumor necrosis factor-α (TNFα) and interleukin-1 β (IL-1β), were determined in human macrophages derived from THP-1 monocytic cells. These cells were exposed to air samples from five occupational settings known to possess high levels of contamination of organic dust: poultry and swine feed industries, waste sorting, poultry production and slaughterhouses. Additionally, fungi and particle contamination of those settings was studied to better characterize the organic dust composition. All air samples collected from the assessed workplaces caused both cytotoxic and pro-inflammatory effects. The highest responses were observed in the feed industry, particularly in swine feed production. This study emphasizes the importance of measuring the organic dust/mixture effects in occupational settings and suggests that differences in the organic dust content may result in differences in health effects for exposed workers.

International audience; Particle fallout in cleanrooms is a primary concern for industries manufacturing critical products with surfaces highly susceptible to particulate contamination. Limited research has been conducted to measure the deposited particles in cleanroom. In the frame of the ISO 14644-3, this paper compares the traditional technique for particle fallout measurements using witness plates to a real-time and in situ measurement done by an innovative device: CLEAPART-100. The CLEAPART-100 detects the same contamination event as optical counters detect. The comparison with the settle plates observed under a microscope shows the loss of particles using that indirect measurement which is unacceptable for an accurate risk analysis assessment.

In spite of the great progress made toward addressing the challenge of particle contamination in nanomanufacturing, its deleterious effect on yield is still not negligible. This is particularly true for nanofabrication processes that involve close proximity or contact between two or more surfaces. One such process is Jet-and-Flash Imprint Lithography (J-FIL™), which involves the formation of a nanoscale liquid film between a patterned template and a substrate. In this process, the presence of any frontside particle taller than the liquid film thickness, which is typically sub-25 nm, can not only disrupt the continuity of this liquid film but also damage the expensive template upon contact. The detection of these particles has typically relied on the use of subwavelength optical techniques such as scatterometry that can suffer from low throughput for nanoscale particles. In this paper, a novel mechanics-based method has been proposed as an alternative to these techniques. It can provide a nearly 1000 × amplification of the particle size, thereby allowing for optical microscopy based detection. This technique has been supported by an experimentally validated multiphysics model which also allows for estimation of the loss in yield and potential contact-related template damage because of the particle encounter. Also, finer inspection of template damage needs to be carried out over a much smaller area, thereby increasing throughput of the overall process. This technique also has the potential for inline integration, thereby circumventing the need for separate tooling for subwavelength optical inspection of substrates.

The contamination of slider air bearing surfaces may lead to a critical failure of hard disk drive systems. The contamination may be classified into two types: the liquid-like contamination and the particle contamination. In this study, the liquid-like contamination is concerned. It is assumed that the liquid-like contamination is caused by the adsorption of contaminant molecules in air. A mathematic model has been developed to predict the accumulating process of the liquid-like contaminant on air bearing surfaces. Numerical analysis of the behavior of the liquid-like adsorbed film for two different types of air bearing surfaces was conducted by using the proposed model based on the Langmuir adsorption. The results show that the contaminant tends to accumulate on the recession area of the air bearing surface when the viscosity of the liquid-like adsorbed film is low. However it may also accumulate in the front area of the air bearing surface when the viscosity is as high as 20 Pa s.

As a result of shrinking dimensions and technology nodes, nanoelectronics manufacturing and handling processes demand growing requirements to the cleanliness of the air inside cleanrooms and microenvironments. Besides the limitation of particle contamination, the limitation of airborne molecular contamination (AMC) is necessary to ensure yield and quality of nanoelectronics production lines.

This study was designed to standardize dust collection in recently built operating theatres equipped with a continuous monitoring system. The objectives were to establish the relationship between microbiological and dust contamination, and then to compare those parameters with the main indicators of surgical activity in order to better define risk factors affecting air quality. The air quality during 23 surgical operations was studied in three conventionally ventilated operating theatres. Microbiological air counts were taken using both passive and active sampling methods. Air dust particles, > or =0.5 and > or =5 microm in size, were measured using a light-scattering particle analyser. The overall dust load was mainly (98%) composed of fine particulate matter, most probably due to its longer suspension time before settlement. These particles positively correlated with operation length, but not with surgical technique, suggesting that fine particles may be a good tracer of operation complexity. In contrast, the surgical technique was the main predictor for the concentration of particles > or =5 microm, with a higher risk from general conventional surgery compared with scope surgery. The frequency of door-opening, taken as an index of staff and visitor movement, was the main negative predictor of over-threshold values of both fine and larger dust particles but, conversely, was a positive predictor of raised bacterial counts.

The lubrication industry strives continuously to meet the evolving needs of the food processing industry. For example, NSF H1 registered food grade lubricants can minimize risks associated with low levels of lubricant contamination in foods and beverages. However, contaminants can compromise the performance of any lubricant. Furthermore, microscopic particle contaminants can cause irreversible damage to machinery. This article discusses sources of contamination, their deleterious effects, methods to measure particle contamination, and means to ensure lubricant cleanliness.

Control of chemical contaminant has become of great importance in addition to particle contamination in a clean room for manufacturing semiconductors, liquid crystal device and other electronics devices. In particular, acid gases, base gases, hydrocarbon gases, boron and phosphor could damage electrical properties of these devices. Therefore, the reduction of contaminant concentration in clean room air is required. In this paper, constitute materials for a clean room newly developed as countermeasure for chemical contamination are introduced. Then, their analysis and evaluation methods for chemical contamination are also described.

The particle contamination on the optical components would degrade the detection performance of the infrared optical systems and even make the detection task failure for the case of the optical components seriously contamitated. With the use of ASAP optical analysis software, a typical infrared optical-mechanical three-dimensional stimulation model has been built up. The particle distributions on the surface of the optical components have been studied and the particle distribution model has also been given. Furthermore, the influence of particle contamination on the stray light radiation characteristic of the infrared optical system has been analyzed in detail. The result shows that contamination particles randomly undergo collisions and small particles are loosely attached to each other at their first contact location and finally deposited as random single-particle aggregation and cluster-cluster aggregation, resulting in an obviously affect on the stray radiation performance of the infrared optical system. Furthermore, the change of the deposition positions of the contaminants aggregation also has a certain influence on the stray light radiation characteristics. In practical applications, it seems particularly important to control strictly over the contamination of optical surface during the operation of the infrared optical system.

In January 2011, Brisbane, Australia, experienced a major river flooding event. We aimed to investigate its effects on air quality and assess the role of prompt cleaning activities in reducing the airborne exposure risk. A comprehensive, multi-parameter indoor and outdoor measurement campaign was conducted in 41 residential houses, 2 and 6 months after the flood. The median indoor air concentrations of supermicrometer particle number (PN), PM10, fungi and bacteria 2 months after the flood were comparable to those previously measured in Brisbane. These were 2.88 p cm−3, 15 μg m−3, 804 cfu m−3 and 177 cfu m−3 for flood-affected houses (AFH), and 2.74 p cm−3, 15 μg m−3, 547 cfu m−3 and 167 cfu m−3 for non-affected houses (NFH), respectively. The I/O (indoor/outdoor) ratios of these pollutants were 1.08, 1.38, 0.74 and 1.76 for AFH and 1.03, 1.32, 0.83 and 2.17 for NFH, respectively. The average of total elements (together with transition metals) in indoor dust was 2296 ± 1328 μg m−2 for AFH and 1454 ± 678 μg m−2 for NFH, respectively. In general, the differences between AFH and NFH were not statistically significant, implying the absence of a measureable effect on air quality from the flood. We postulate that this was due to the very swift and effective cleaning of the flooded houses by 60,000 volunteers. Among the various cleaning methods, the use of both detergent and bleach was the most efficient at controlling indoor bacteria. All cleaning methods were equally effective for indoor fungi. This study provides quantitative evidence of the significant impact of immediate post-flood cleaning on mitigating the effects of flooding on indoor bioaerosol contamination and other pollutants. Keywords: Indoor air, Particle number, PM10, Fungi, Bacteria, Indoor dust

This paper presents a method for reducing particle contamination on sliders. A model for simulating particle movement in an air bearing is developed and solved numerically. Through the simulation, the paths of particles moving in the air bearing are studied for various designs of sliders. It is found that some slider designs have good characteristics that make most of the particles entering the air bearing leave the slider from the sides instead of from the trailing edge, which is regarded as beneficial to reduce the particle contamination on the sliders.

Monitoring of particle contamination by statistically based methods is used extensively in semiconductor manufacturing. Often Shewhart-type control charts are used for this purpose. These charts suffer from some potential disadvantages in this application environment. Specifically, they are slow to detect shifts or changes in the level of particle contamination and, in some situations, the underlying statistical assumptions of the charts are inappropriate for contamination data. We suggest the use of cumulative sum and exponentially weighted moving average control charts for monitoring particle contamination. The advantages of these charts for the types of particle contamination data typically encountered in semiconductor manufacturing are discussed and illustrated with examples.

The importance of controlling airborne particle contamination in clean rooms and wafer environment is well-known and much effort has been devoted to keep the particle contamination from wafer environment. Table 1 shows particle detection limit on wafer suggested by ITRS 2012 that is desirable in the future flash half pitch size. It indicates wide diameter range of airborne particles, from the size smaller than 100 nm, is required to be detected and controlled with the device pattern size becoming smaller and smaller. This study is focused on particle contamination from clean rooms into wafer environment. Front opening unified pods (FOUP) and equipment front end modules (EFEM) were taken as an example of wafer environment. Furthermore, the possible future work on keeping the contamination from wafer environment was discussed.

Contamination-sensitive space flight hardware is typically built in cleanroom facilities in order to protect the hardware from particle contamination. Forest wildfires near the facilities greatly increase the number of particles and amount of vapors in the ambient outside air. Reasonable questions arise as to whether typical cleanroom facilities can adequately protect the hardware from these adverse environmental conditions. On Monday September 6, 2010 (Labor Day Holiday), a large wildfire ignited near the Boulder, Colorado Campus of Ball Aerospace. The fire was approximately 6 miles from the Boulder City limits. Smoke levels from the fire stayed very high in Boulder for the majority of the week after the fire began. Cleanroom operations were halted temporarily on contamination sensitive hardware, until particulate and non-volatile residue (NVR) sampling could be performed. Immediate monitoring showed little, if any effect on the cleanroom facilities, so programs were allowed to resume work while monitoring continued for several days and beyond in some cases. Little, if any, effect was ever noticed in the monitoring performed.

Publisher Summary This chapter explores basics and sampling of particles for size analysis and identi?cation. Contamination in particle form can originate from the facility, from tooling and work surfaces, from the piece parts, from indirect materials and packaging, and from people. These categories have been discussed to provide a better understanding of the complexity of sources that must be considered in a particle contamination control program. Particles can be sampled from air, compressed gases, liquids, and surfaces. One of the most common applications of sampling of airborne particles occurs in cleanrooms, both to demonstrate regulatory compliance and to maximize yield and reliability. In order to plan sampling locations, considerable focus has been placed on the air?ow in cleanrooms. It is found that when performing airborne particle sampling in a cleanroom, clean bench, or minienvironment, air?ow visualization and air velocity measurements are made. These measurements show problems that are likely to contribute to contamination problems. Some simple examples of methods for correcting air?ow problems are also elaborated.

The introduction of EUV Lithography for the next node has two major obstacles at the moment; the first is source power and reliability and the second is defect free reticles and damage free cleaning of reticles. We present our results on our investigation for damage free cleaning of EUV reticles with remote plasma cleaning for molecular (carbon) contamination and nanobubbles for particle removal. We believe that a multi step approach is necessary for cleaning of reticles as a single cleaning step will not be sufficient for the efficient removal of molecular as well as particle contamination. Remote plasma seems to be the favorable technique for carbon cleaning and repeated cleaning up to 85 nm of carbon removal shows no degradation of the reticle material. © 2012 SPIE.

An analytical chemistry clean room was established by renovating an ordinary chemistry laboratory; 8.75x8.20x2.9 meters3. The main aim is to develop a contamination free area for trace and ultratrace analysis of metals. The metallic parts in the laboratory were either replaced by high quality polymer material or covered with epoxy paint. The walls, floor and ceiling were covered with good quality wall paper (avoiding the metal base colors) and epoxy paint. Polymer sheet with adhesive was used to cover the laboratory bench and the working area in the fume hood. In designing the clean room , the necessary feature is to keep the room free from particle contamination. The air circulating in the clean room is controlled by the HEPA filter and a modified air conditioner to provide an air inlet of 1,000 CFM and an outlet of more than 850 CFM, the loss is due to the sucking motor for GFAAS and fume hood. Essential equipment situated in this clean room are laminar flow work station, high purity water unit...

A study was initiated in an IC manufacturing clean-room in Allentown, Pennsylvania to evaluate ultrafine airborne particle contamination in the processing environment. Airborne concentrations of > 0.01μm particles were continuously monitored at live locations within the cleanroom. The data exhibited a background concentration of typically 50–100 particles/ft3 on which were superimposed “hot spot” incidents with concentrations as high as 105 particles/ft3. A statistical evaluation was undertaken to find explanations for (a) the short term readings of high particle concentration and (b) longer term fluctuations in the background levels. No correlations across sampling locations were found for (a), indicating that the majority of these events were caused by very localized activities within the cleanroom. There were also no correlations between the event frequency for high particle concentrations and time of day, except that few events were evident when the cleanroom was quiet. For example, no such events wer...

The hazardous effects due to the insoluble microparticles generated in the injections have been pointed out. To our knowledge, however, there have been no reports about insoluble microparticulate contamination at ampoule opening. Therefore, we performed this study to evaluate the relationship between time and glass particulate sedimentation to examine the effect of swabbing the ampoule neck on particle generation to clarify the relationship between the inner-diameter size of an ampoule and the amount of glass particulate sedimentation to find out the effect of methods for ampule opening, and compare particle contamination in glass ampoule and that of plastic, after ampoule opening and assessed the contribution of material of ampoule to the particle generation. We observed that the glass particulate contamination of accumulation value at a size over 2 mum increased significantly after 60 seconds, the swabbing the neck of the ampoule prior to opening had a negative effect on prevention of glass particulate contamination, the glass particulate contamination was positively influenced by the inner-diameter size of the ampoule, but not by the thickness of the ampoule walls, the particulate contamination derived from glass significantly increased by general method as well as using ampoule open adaptor compared with our method, and the insoluble microparticulate contamination in plastic ampoule was significantly lower than that in glass ampoule. The present findings might provide an useful information to reduce glass particules after ampoule opening performed in clinical practice.

One closed-loop and eight single-pass plutonium production reactors originally operated on the Columbia river. During the 26 years of single-pass reactor operations, small amounts of radioactive particles were released in liquid discharges to the Columbia river and were deposited in sediment and cobble along the shoreline and on islands in the river. Islands located adjacent to D island and immediately downstream of D island had the greatest density of particles. In 1979, the small particles contained between 63 and 890 kBq of cobalt-60 activity. Dose rates emanating from those particles ranged from 1 to 14 microGy h(-1). Because of the short half-life of cobalt-60 (5.3 y), the hot-particle problem at Hanford has taken care of itself through radiological decay. Some scientists have proposed that it is economically and environmentally advantageous to manage isolated low-level contaminated sites with institutional controls until the activity decays and the sites can be released rather than to pursue expensive clean-up options.

High power laser systems require nearly contamination free optics to maintain desired transport efficiency and to minimize optic damage. The required cleanliness is generally achieved through practices that preclude or remove foreign particle contamination. However, laser optic systems may also be contaminated by vapor-borne contaminants from material outgassing, by particles ablated from surfaces exposed to amplifier or laser light, or by contact with items used in the production and cleaning of optics and components. To minimize such contamination on the optics of the National Ignition Facility (NIF), a rigorous screening test program was introduced. This test program replicates conditions in the beam path as well as conditions during production and cleaning. The former is represented by sol-gel exposure tests and by subjecting materials to amplifier flashlamp light and 1ω laser light. The latter is represented by organic solvent extraction tests and surface contact tests for items that could contact optic surfaces. This paper will discuss the methodology for, and administration of, these tests and present results for selected materials.

In this three-stage study, we test the hypothesis that supplementary cleaning with potassium permanganateor =4 mg.l(-1) eliminates protein and particle contamination from the reusable Classic laryngeal mask airway. The first stage involved supplementary cleaning of 70 1 x 1 cm segments from deliberately contaminated laryngeal mask airways using potassium permanganate at 0, 2, 4, 8, 16, 32 and 64 mg.l(-1) and testing for protein staining. This showed that the lowest concentration required to eliminate protein contamination was 8 mg.l(-1). The second stage involved supplementary cleaning of 50 used laryngeal mask airways with either potassium permanganate 8 mg.l(-1) or saline and testing for protein staining. This showed that protein contamination was lower in the potassium permanganate group (p0.00001): all laryngeal mask airways in the control group and none in the potassium permanganate group were contaminated. The third stage involved scanning electron microscopic examination of 1 x 1 cm segments from three laryngeal mask airways used in the control group, three from the potassium permanganate group, plus three brand new laryngeal mask airways. The mean density ofor =1 mum surface particles was lower in the potassium permanganate 8 mg.l(-1) than the control group (21 vs. 121 .cm(-2), p0.0001) and was similar to brand new laryngeal mask airways (24 .cm(-2)). We conclude that supplementary cleaning with potassium permanganate 8 mg.l(-1) eliminates protein deposits from reusable laryngeal mask airways and reduces particle contamination to similar levels to brand new laryngeal mask airways.

A key lesson learned from the earliest optics installed in the National Ignition Facility (NIF) was that the traditional approach for maintaining cleanliness, such as the use of cleanrooms and associated garments and protocols, is inadequate. Assembly activities often negate the benefits provided by cleanrooms, and in fact generate contamination with high damage potential. As a result, NIF introduced ''clean assembly protocols'' and related practices to supplement the traditional clean room protocols. These new protocols included ''clean-as-you-go'' activities and regular bright light inspections. Introduction of these new protocols has greatly reduced the particle contamination found on more recently installed optics. In this paper we will describe the contamination mechanisms we have observed and the details of the clean assembly protocols we have successfully introduced to mitigate them.

The problems encountered in the transmission of high-power (kilowatts to megawatts) in extraterrestrial environments are reviewed. A summary of the work at Auburn University in the study of these problems is presented. These studies include high-voltage breakdown in the space environment as influenced by gas contamination and thermal stress, the modeling of lunar transmission lines, particle contamination, and material degradation by the hypervelocity impact of microparticles.

Various cleaning methods are available depending on the sizes of the parts, mounted or unmounted, and purpose of the cleaning. Dust and other particle contamination affect scattering and act as nuclei for defects in optical coatings. In some cases, these defects can initiate laser damage. Noncontact cleaning methods to eliminate particle contamination include blowing large particles from surfaces with an air bulb, "canned air," or a nitrogen gas jet, for a gentle cleaning and CO2 snow for more aggressive particle removal. Laser assisted particle removal is a new high tech method. A strip coating material applied to the surface and subsequently removed will remove large fresh particles and often fingerprints. Contamination films affect the quality and adherence of optical coatings. These are usually removed (from unmounted optics) by cleaning the surface in a detergent and water bath followed by extensive rinsing and non-contact drying. Alternate methods when immersion in water is not possible are drag wiping, or spraying or squirting organic solvents over the surface. Before cleaning, surfaces must be visually inspected to determine the type and location of the contamination, to decide if cleaning is necessary, and what type of cleaning technique to use. Finally, bad cleaning is much worse than no cleaning! Illustrations of the cleaning methods described above will be given.

The process performance of the Axcelis Technologies MC3, medium current implanter for 300 mm wafers, is reviewed. The MC3 is based on an evolutionary design approach. It uses proven beam transport, electrostatic scanning, beam parallelism, and energy purity schemes based on the successful 8250/sub HT/ design. Metals contamination, beam parallelism, energy purity, particles, and dose uniformity and repeatability are reviewed. The results show that metals contamination, parallelism, and particle contamination are better than those for the 8250/sub HT/. Energy purity, dose repeatability and uniformity are similar to the ones achieved with 8250/sub HT/.

In this paper, a new method of reducing particle contamination in semiconductor manufacturing is suggested. The factors of particle contamination are first listed by dividing the equipment into several blocks and several units. Then, these factors are investigated in order. In such a way, it becomes clear how the equipment generates the particles and where the particles move. Thus, we can take suitable measures to reduce particles.

Metal 1 sidewall polymer contamination was investigated in wafer fabrication. SEM and EDX techniques were used to identify the root cause. After metal 1 etching, particle contamination was found on metal 1 lines. Cross sectional SEM results showed the contamination was at the side of the metal lines. EDX results showed that C and Cl elements were detected. Failure analysis results indicated that the contamination was most likely sidewall polymer introduced during metal etching. Further fab investigation found that the sidewall polymer contamination was due to gas flow drifting from set point during metal etches. The solution is that the mass flow control is calibrated using two set points (at 30 and 60 sccm). This new calibration procedure was able to detect the MFC linearity problem. After implementing the two point calibration method, the sidewall polymer contamination was eliminated.

The design stress of sulphur hexafluoride Gas Insulated Switchgear (GIS) systems are limited by the harmful effects resulting from the almost inevitable presence of particulate contamination in GIS equipment. Mixing SF/sub 6/ with other gas is a possible way of improving GIS performance under particle contamination condition. This paper studies the breakdown of SF/sub 6/-gas mixture (SF/sub 6/-air, SF/sub 6/-N/sub 2/ and SF/sub 6/-C/sub 4/) in the presence of contaminating particles under applied DC voltage. The effect of particle dimensions on the breakdown voltage and so on the particle contamination factor (PCF) is presented in this work. The breakdown voltage-pressure characteristics for SF/sub 6/-gas mixture with different fractional concentration of SF/sub 6/ in mixture are carried out. Also, the particle contamination sensitivity is sought for different parameters and to obtain the optimum SF/sub 6/-gas mixtures for the case study. From this study it is concluded that some SF/sub 6/-gas mixtures have breakdown gradients comparable to that of pure SF/sub 6/ and are less sensitive to the presence of strong localized fields.

The concentrations of selected air quality parameters in aircraft cabins were investigated including particle numbers in cabin air compared to fresh air and recirculation air, the microbiological contamination and the concentration of volatile organic compounds (VOC). The Airbus types A310 of Swissair and A340 of Lufthansa were used for measurements. The particles were found to be mainly emitted by the passengers, especially by smokers. Depending on recirculation filter efficiency the recirculation air contained a lower or equal amount of particles compared to the fresh air, whereas the amount of bacteria exceeded reported concentrations within other indoor spaces. The detected species were mainly non-pathogenic, with droplet infection over short distances identified as the only health risk. The concentration of volatile organic compounds (VOC) were well below threshold values. Ethanol was identified as the compound with the highest amount in cabin air. Further organics were emitted by the passengers - as metabolic products or by smoking- and on ground as engine exhaust (bad airport air quality). Cleaning agents may be the source of further compounds.

This paper describes a finite-element numerical approach for predicting the time-dependent particulate motion of released particulate that complements the standard particulate redistribution model for predicting contamination levels of exposed payload surfaces during the ascent-phase. The particulate redistribution model is used to give a spatially and time averaged estimate of the contamination level during ascent that is considered to be very conservative. All particulates are assumed to be retained in the fairing/payload volume with none venting out of the volume. The new numerical model takes more comprehensive approach and attempts to estimate the time-dependent particulate surface-impingement flux by considering the key physical mechanisms believed to govern the gas/particulate transport problem. It solves the time-dependent fairing/payload gas transport (venting) and particulate transport problem during the ascent-phase. The gas transport model is used only up to point where gas flow no longer significantly impacts the partiality motion. Thus, only the continuum fluid regime is considered in the model. It is possible to treat particulate release beyond this point, but it has not been considered in the modeling effort described in this paper. Booster acceleration, gas motion during venting and particulate drag (due to gas flow) are treated. Released particulate trajectories and particulate impingement fluxes are predicted, and subsequent surface contamination levels are estimated. Results are presented for both Pegasus/TOMS and EOS during ascent. The final contamination levels predicted are considered to be the initial on-orbit particulate contamination levels.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper provides results from a study that characterized the particle distributions found from variable contaminated airstreams in energy recovery ventilators (ERV) during two different test scenarios. The first scenario involved the measurement of the particulate concentrations during an operational situation when the pressure differential forces cross-flow leakage between the exhaust and intake streams. The second scenario involved the characterization of aerosol particulate concentrations from the carry-over contamination when the wheel was not in operation. The findings from the study concluded that if a source of aerosol particulate matter is present in an environment utilizing an ERV system, then cross-over and carry-over contamination will occur proportionally to the amount of aerosol particulate matter released into the system.

Control of contamination on the surface of wafers during the manufacture of state-of-the-art microcircuits is imperative if high yields are to be obtained. Hence, wafers are often cleaned using a modified RCA clean to remove organic, metallic and particle contamination prior to microcircuit manufacture. Recently, wafers obtained from a particular vendor were found to have heavy particle contamination after a modified RCA clean. The wafers were also found to have a hydrophobic surface indicating the presence of heavy organic contamination. Analysis of the wafer surface revealed that it was covered with film of a polydimethylsiloxane-like compound. The source of the compound was found to be a gasket in the storage boxes used to transport the wafers. This paper describes the methodology used to identify the source of the contaminant and the cleaning methods developed to eliminate the particle contamination which it caused.

This paper reviews the application of light scattering to the detection and measurement of discrete contaminating particles on smooth surfaces. The optical properties of specular and diffuse reflecting surfaces, and those of isolated particles are summarized, followed by the behavior of surface-deposited particles. A discussion is presented on the parameters influencing the detectability of particles on surfaces, and the principal design criteria of light scattering inspection systems. Emphasis is placed on laser scanning systems which, at present, predominate as a versatile means of automated surface contamination detection. Both laser scanning and video inspection systems are discussed, and examples are presented of typical commercially available instruments incorporating these techniques.

A scaled dc transmission line insulator string has been implemented in sub-corona experiments to identify parameters important to the particle contamination process. Simple trajectory analysis of particle motion yields good agreement between predicted contamination features and observed phenomena, and suggests a model for the quantitative prediction of contamination of dc insulators on actual transmission lines in the field. The deposition rate on surfaces that become contaminated is experimentally shown to be given by the average product of particle mobility, particle mass density in the ambient air, and normal electric field on the insulator surface.