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SAND is very harmful to engines. During recent tests conducted by me in the North African Deserts, as much as half a pound of sand has been collected in ten minutes in each air intake of a Mosquito aircraft taxying, alone, downwind on a desert airfield. Had the Mosquito been following another aircraft, or had its air intake been situated lower, the quantity of sand would have been much larger. Under such conditions the importance of having efficient air cleaning intakes fitted to every aircraft engine is obvious. Sandy conditions are not confined to desert airfields, some airfields in this country and on the Continent are as bad.

Purpose – Emissions trading is often heralded as an efficient approach to environmental regulation. In the mid-90s Communities for a Better Environment (CBE), a Los Angeles-based advocacy organization, raised concerns that emissions trading in the South Coast Air Basin, the most polluted region in Southern California, would result in environmental injustice. The organizations concerns received mixed responses from regulators. Historical analysis is used to assess the clash between emissions trading and environmental justice (EJ).

Methodology/approach – Emissions trading and EJ arose side by side between the 1960s and the 1990s, yet they disagree on how to clean the air. Historical analysis of legal documents, presidential addresses, letters, working papers, reports, and the like offers a better understanding of the development of emissions trading and EJ, and their intersection in environmental policy.

Findings – Emissions trading was grafted onto Clean Air Act policies not inherently designed for their incorporation. As a result, emissions trading came into direct philosophical opposition with EJ as political pressures calling for both economically efficient antiregulatory-ism and environmental equity forced their intersection. Formally, regional and national government accepted EJ as part of law. However, in principle, emissions trading undermined this acceptance. As a result, CBE could not easily win or explicitly lose its battle against emissions trading.

Originality/value of paper – Previous work on the relationship between emissions trading and EJ tend to focus on legal analysis and normative implications of emissions trading. Putting emissions trading and environment justice into historical perspective helps to illuminate larger questions about EJ activism and policy. Also, as California, the United States, and Europe turn to emissions trading to combat not only air pollution but also climate change, important lessons can be learned from the histories and collision of emissions trading and EJ.

In a paper presented to the Society of Automobile Engineers at Seattle in August, H. M. Turner, of the Donaldson Company, Inc. gave a paper on air cleaners, and discussed the choice of wet or dry cleaners, and put the case for a composite type of dry air cleaner. Fig. 1 shows the importance of air filters in the case of rock crushers and earth moving equipment of all types. The rock crusher air cleaner has to handle 1,300 times the dust that the automobile air cleaner does, more than 100 times that of the farm tractor and about 6 times that of the crawler tractor.

Surface preparation—Reasons and Methods To determine the reason why we prepare the metal surface, we first consider the end result we wish to achieve. Exposure to the elements will rapidly corrode metals and lead to destruction by erosion, particularly in salt‐laden air. We must, therefore, bond on to this surface a complete barrier to external destruction by means of a protective coating. (We do not ‘paint the boxes’, we apply a protective coating).

Indoor biocontamination is recognized as a potential public health problem. The concentration of indoor pollutants is varied, depending on air filtration, air distribution systems and air cleaning devices. One portable air cleaning device, “Ionizer Air clean‐er/Air clinic” was investigated. The ability of particles to remain airborne or pass through filters depends on the size and density of particles. Air clinic device removed bacterial and mould contaminants in efficiencies up to 98.7 per cent and 67 per cent respectively, after 30 minutes of operation. After purification, Penicilliumspecies were predominant. Small particles (≤q4μm) are passed through filter mates. The negative ions produced by the device are effective for removing suspended particulates in efficiency up to 99 per cent. The disadvantages of this device are: the need to change the filter after short period of operation, and the unpleasant odour emitted from the device during operation due to ionization of particles.

The next month or two behind us and this decade will have passed, to merge in the drab background of the post‐war years, part of the pattern of frustration, failure and fear. The ‘swinging sixties’ some called it, but to an older and perhaps slightly jaundiced eye, the only swinging seemed to be from one crisis to another, like the monkey swinging from bough to bough in his home among the trees; the ‘swingers’ among men also have their heads in the clouds! In the seemingly endless struggle against inflation since the end of the War, it would be futile to fail to see that the country is in retreat all the time. One can almost hear that shaft of MacLeodian wit christening the approaching decade as the ‘sinking seventies’, but it may not be as bad as all that, and certainly not if the innate good sense and political soundness of the British gives them insight into their perilous plight.

Cleanrooms are highly controlled enclosed rooms where air quality is monitored and ensured to have less contamination according to standard cleanliness level. Air filters are used to optimize indoor air quality and remove air pollutants. Filter media and filtering system are decided as per requirement. Depth filter media are mostly used in cleanroom filtrations. This paper aims to present a comprehensive review of the evolution of cleanroom filter media. It evaluates the advantages and disadvantages of air filter media. It is also studied which air filters have additional properties such as anti-microbial properties, anti-odour properties and chemical absorbent. Development and innovation of air filters and filtration techniques are necessary to improve the performance via the synergistic effect and it can be a possible avenue of future research.

This paper aims to drive the future of air filter research and development in achieving high-performance filtration with high filtration efficiency, low operational cost and high durability. Air pollutants are classified into three types: suspended particles, volatile organic pollutants and microorganisms. Technologies involved in purification are filtration, water washing purification, electrostatic precipitation and anion technology. They purify the air by running it through a filter medium that traps dust, hair, pet fur and debris. As air passes through the filter media, they function as a sieve, capturing particles. The fibres in the filter medium provide a winding path for airflow. There are different types of air filters such as the high-efficiency particulate air filter, fibreglass air filter and ultra-low particulate air filter.

Emerging filtration technologies and filters such as nanofibres, filters with polytetrafluoroethylene membrane are likely to become prevalent over the coming years globally. The introduction of indoor air filtration with thermal comfort can be a possible avenue of future research along with expanding indoor environment monitoring and improving air quality predictions. New air filters and filtration technologies having better performance with low cost and high durability must be developed which can restrict multiple types of pollutants at the same time.

The systematic literature review approach used in this paper highlights the emerging trends and issues in cleanroom filtration in a structured and thematic manner, enabling future work to progress as it will continue to develop and evolve.

Wherever solvents and solvent containing systems are employed, protection for people and the environment is a vital factor in the way that they are used. The paper addresses the following: Minimum contamination of the environment (air and water) by solvent emission; adherence to existing occupational safety laws: process technology and equipment that ensure high safety levels, and non polluting waste disposal.

Today's electronic assembly manufacturing operations can be complex combinations of process steps such as IR reflow, wave soldering, special soldering of connectors or sensitive components, cleaning, rework, etc. Such multiple exposures to elevated temperatures and/or oxidising environments (e.g., aqueous cleaning) can have a negative effect on the solderability of printed wiring board (PWB) surfaces. This in turn may limit the effectiveness of subsequent soldering operations, such as wave soldering following an IR reflow step. The purpose of this study is to assess the impact of individual assembly process steps on the solderability of PWB surfaces. The PWB surfaces are initially treated with protective coatings of benzotriazole (BTA). The process steps investigated include: IR reflow in air and in nitrogen; vapour phase reflow; aqueous cleaning; adhesive cure; and wave soldering as a function of solder temperature and flux type. Meniscograph wettability testing is used to measure relative solderability changes, and Auger electron spectroscopy (AES) is used to monitor surface chemical changes, particularly oxide formation. The overall result is a body of fundamental information providing insight into optimisations of process flows, equipment operating specifications, process temperatures and selection of flux types.