The measurement of air supply volumes and velocities in cleanrooms

Air supply volumes and velocities in cleanrooms are monitored by airflow measuring hoods and anemometers but these measuring methods can be inaccurate if used incorrectly. It is demonstrated in this article that measuring hoods are accurate if the air supply passes evenly out of the hood, as occurs when the air volume is measured from a four-way diffuser or no air supply diffuser. However, when a swirl diffuser was investigated, the measuring hood gave readings more than 50% greater than the true volume. The reasons for the inaccuracy, and methods to correct it were established. Vane anemometers give inaccurate readings at the face of high-efficiency air supply filters, and it was found that the most accurate reading was found about 15 cm from the filter face. The number of readings required across the filter face to obtain an accurate average velocity was investigated, as was a scanning method using overlapping passes

Removal of microbe-carrying particles by high efficiency air filters in cleanrooms

The removal efficiency of high efficiency air filters against microbe-carrying particles (MCPs) in the air supply of occupied rooms, such as cleanrooms, was determined. Knowing the size distribution of MCPs in the air to be filtered, and the removal efficiency of a filter against individual particle diameters, the overall removal efficiency was ascertained. A variety of filters were investigated, and it was found that a filter 90% efficient, when tested against sub-micrometre particles, used in standard classification methods such as EN 1822, was greater than 99.99% efficient in removing MCPs. The effect of filter efficiency on the quality of the air supply, and the concentration of MCPs in cleanroom air was also studied. No practical improvement in airborne concentrations was obtained by filters that had a removal efficiency greater than 99.99% against MCPs. Use of a filter suitable for removing MCPs, rather than sub-micrometre particles, would give a reduction of about 6 to 8-fold in the pressure drop over a filter, and a substantial reduction in the cost of running a cleanroom

Weaving a "Hybrid Mat": Samoa meets the Solomons.

Developed nations providing aid and educational support for less wealthy countries, have frequently imposed their own ideas and practices in a top-down manner. A recent collaborative aid project between the New Zealand and Solomon Islands Governments, has been more equitable by developing the project as a "Partnership". As a New Zealander involved with this project, I found participation in the Partnership activities to be rewarding and enlightening. The metaphor of a "hybrid mat" is used to weave together narratives from my pre-Partnership life and career events with narratives from my partnership experiences. Clandinin and Connelly's renowned concept of "stories" is utilised throughout to illustrate how perceptions of events can vary from person to person. "Cover" stories (the "official" narrative of events for outsiders); "secret" stories (narratives available only to insiders); and "re-storying" (placing a story within a context/place and negotiating the meanings of the story) are concepts used to illustrate the complexity and multiple explanations and understandings that come from narratives. It is through "re-storying" the combined "cover" and "secret" stories that a third space of understanding is revealed. This article traces the process and product of understanding and re-storying a particular "hybrid mat" for the writer

Experimental and CFD airflow studies of a cleanroom with special respect to air supply inlets

Investigations were carried out into the airflow in a non-unidirectional airflow cleanroom and its affect on the local airborne particle cleanliness The main influence was the method of air supply A supply inlet with no diffuser gave a pronounced downward jet flow and low levels of contamination below it, but poorer than average conditions in much of the rest of the room A 4-way diffuser gave much better air mixing and a more even airborne particle concentration throughout the cleanroom Other variables such as air inlet supply velocity, temperature difference between air supply and the room, and the release position of contamination also influenced the local airborne cleanliness A CFD analysis of airflow fields in a cleanroom was compared with measured values It was considered that a turbulent intensity of 6%, and a hydraulic diameter based on the actual size of the air inlet, should be used for the inlet boundary conditions and, when combined with a k-epsilon standard turbulence model, a reasonable prediction of the airflow and airborne particle concentration was obtained

Taking time to understand: articulating relationships between technologies and organizations

Dynamic relationships between technologies and organizations are investigated through research on digital visualization technologies and their use in the construction sector. Theoretical work highlights mutual adaptation between technologies and organizations but does not explain instances of sustained, sudden, or increasing maladaptation. By focusing on the technological field, I draw attention to hierarchical structuring around inter-dependent levels of technology; technological priorities of diverse groups; power asymmetries and disjunctures between contexts of development and use. For complex technologies, such as digital technologies, I argue these field-level features explain why organizations peripheral to the field may experience difficulty using emerging technology

Value of Joint Programs Underestimated

[Excerpt] I am happy to comment on a provocative monograph that raises important issues for union policies and strategies. The authors make two main points: 1. Unions should be proactive in developing worker participation programs in industry and should push them beyond the shopfloor into strategic economic and technological issues. 2. As far as possible, worker participation programs should be controlled by the union. Union leaders should firmly reject programs jointly controlled by union and management. I agree with the first point and disagree with the second. I also question what I see as a bias in selecting case examples to support the Banks-Metzgar thesis. If authors are free to choose any cases to support their arguments, they can prove almost anything

Assessment of degree of risk from sources of microbial contamination in cleanrooms; 2: surfaces and liquids

The degree of risk from microbial contamination of manufactured products in healthcare cleanrooms has been assessed in a series of three articles. The first article discussed airborne sources, and this second article considers surface contact and liquid sources. A final article will consider all sources and give further information on the application of the risk method. The degree of risk to products from micro-organisms transferred from sources by surface contact, or by liquids, has been assessed by the means of fundamental equations used to calculate the likely number of microbes deposited (NMD) onto, or into, a product. The method calculates the likely product contamination rate from each source and gives a more accurate risk assessment than those presently available. It also allows a direct comparison to be made between microbial transfer by different routes, i.e. surface, liquid and air

Deposition velocities of airborne microbe-carrying particles

The deposition velocity of airborne microbe-carrying particles (MCPs) falling towards surfaces was obtained experimentally in operating theatres and cleanrooms. The airborne concentrations of MCPs, and their deposition rate onto surfaces, are related by the deposition velocity, and measurements made by a microbial air sampler and settle plates allowed deposition velocities to be calculated. The deposition velocity of MCPs was found to vary with the airborne concentration, with higher deposition rates occurring at lower airborne concentrations. Knowledge of the deposition velocity allows the deposition on surfaces, such as product or settle plates, by a known airborne concentration of MCPs to be predicted, as well as the airborne concentration that should not be exceeded for a specified product contamination rate. The relationship of airborne concentration and settle plate counts of MCPs used in Annex 1 of the EU Guidelines to Good Manufacturing Practice to specify grades of pharmaceutical cleanrooms was reassessed, and improvements suggested

"I Saw You": searching for lost love via practices of reading, writing and responding

How do emotions move and how do emotions move us? How are feelings and recognitions distributed socio-materially? Based on a multi-site ethnographic study of a romantic correspondance system, this article explores the themes of love, privacy, identity and public displays. Informed by ethnomethodology and actor-network theory its investigations into these informal affairs are somewhat unusual in that much of the research carried out by those bodies of work concentrates on institutional settings such as laboratories, offices and courtrooms. In common with ethnomethodology it attempts to re-specify some topics of interest in the social sciences and humanities; in this case, documents and practices of writing and reading those documents. A key element of the approach taken is restoring to reading and writing their situated nature as observable, knowable, distributed community practices. Re-specifying topics for the social sciences involves the detailed description of several situated ways in which the romantic correspondence system is used. Detailing the translations, transformations and transportations of documents as 'quasi-objects' through several orderings, the article suggests that documents have no essential meaning and that making them meaningful is part of the work of those settings