Count the particles


Tony Sands talks about particle counting and its relativity and relevance, with particular reference to Optical Sciences Ltd

Consider the "man in the street". Is he thinking about particle counting while he shops, drinks his pint or waits for his bus? This would be highly unlikely unless he has an industrial background which brings him into direct contact with gases, liquids, food production, pharmaceuticals, oils or medical environments. The number of workers worldwide in these industries is small compared to our ever-increasing population. Understanding and using the science of particle counting, while essential to a tiny minority in controlling certain critical processes and techniques, is not widespread. The control we exercise over – or indeed the detailed knowledge we have about – our immediate personal environment outside these specific cases varies from minimal to non-existent. Mankind itself is a prime culprit for generating particulate pollution in our own personal environment, seriously contaminating the planet. The evidence of his activities in the pollution of atmosphere, ocean, soils and the upper atmosphere is not hard to find on a universal scale. Furthermore, the human race has some unfortunate traits in that only when an ultraclean environment is essential to achieving a commercial result will consideration be given to controlling the environment, representing a perverse kind of industrial selfishness. Historically, the areas of technology leading to the most financial reward have always been entered into with scant regard for the long-term environmental consequences. Examples being both fossil and nuclear fuelled power generation, petrol and diesel emissions, the spread of GM crop spores and, of course, the deterioration of the ozone layer, which alone could well finish mankind's abuse of the planet somewhat dramatically in the not too distant future. Fortunately for the processes requiring particulate monitoring, there is a growing science of particle detection, counting and analysis in both gaseous and liquid environments. It is again unfortunately true that the most compelling reasons for exercising detailed environmental control is not altruistic but imperative in order to achieve the specific commercial goals. For example: • Pharmaceutical preparations must be pure and consistent, otherwise the products could be unsafe • Cleanroom conditions are essential in medical surgery, otherwise infection and mortality occurs • Semiconductor manufacture, creating the tiny elements for computers using nanotechnology (building products on a molecular scale), must be totally uncontaminated, otherwise the computers that control our lives would be unreliable • Aircraft and commercial vehicle oils must be pure and particle free to avoid wear and tear, and failure in service • Saline and glucose drips for hospital patients must be uncontaminated and pure • Fluid logic systems which control chemical and major industrial plant processes must be reliable to avoid catastrophic failure. We have indicated that it is, at the same time, possible, desirable and essential to exercise the science of detecting alien particulate matter. In some cases (such as emulsions and suspensions in liquids) the presence of such particles may not be alien but indeed desirable in closely controlled quantities. We can see, therefore, that when we have to do something we react by developing the technology. But what of the "man in the street" we mentioned earlier? He is still waiting for his bus and breathing in significant quantities of particulate matter – some, if not most of which, could well have been generated by the very industrial processes that require ultra clean environments for their own survival and proliferation. A real environmental paradox. OptiCal Sciences Ltd of Northampton is a developing company specialising in devices and services for particle detection and size analysis. Started in 1996 by husband and wife team Ian and Wendy Askew, OptiCal Sciences supplies, calibrates and services a comprehensive range of equipment for:

• Particle counting • Cleanroom validation • Photometer filter testing • Aerosol generation • Liquid particle detection • Bottle sampling systems

On-site services and hire feature prominently in OptiCal's activities. Equipment available ranges from the very latest small, light, hand-held fully featured particle counter – the CLiMET® CI-550 illustrated in this article – through to complete installations with facility monitoring using a unique software package known as "Wonderware". The contamination spectrum and particle level which is considered adequate, for example, in pharmaceutical manufacturing of sterile products is quite specifically laid down in legislation as being typically a Class A EU cGMP (1997) or ISO-14644-1 class 5 environment. The spectrum must not include particles above 5.0µm in diameter and there must not be any of them in a cubic foot of sampled air. The spectrum shown in Fig. 1 – Cleanroom would be typical of a Pharmaceutical Manufacturing sterile area. We have actually carried out this measurement as a site test for our newest portable unit and a typical result is shown in Fig. 1 – Outside. As you can see we have a particle count in excess of 2.0 million and particle sizes ranging from 0.3µm to 5µm in diameter. This looks like a factor of 106 worse than the pharmaceutical case. In a city environment, going from the smallest at sub micron level, we have bacteria, dust and wheat germ, particularly if we are in the season for hay fever. The 1-10µm range would contain the sulphur and lead-based by-products of combustion and industrial pollution. Larger again, in the range 1-100 would be fabric hairs and airborne pieces of structural substances such as bricks and concrete particles carried on the wind and the largest item perhaps would be a world cup football from a Beckham free kick. It is possible to give accurate illustrations from our database of environments. Fig. 1 – Office shows a typical office reading. Obviously the office is a marginally cleaner spectrum than the street. The pattern, however, typifies a number of unfiltered environments and is usually made up of carpet dust and airborne fabric particles. Such would also be the case in a home environment, with a similar concentration of dust but also particles in the size range where dust mites and living organisms are found. These can cause allergies and in some cases carry infectious diseases. In the case of controlled industrial environments, standards exist which define acceptable levels. As stated earlier, these levels are necessary to prevent things going seriously wrong with a process. With regard to the "man in the street", or for that matter in the workplace, there is a health issue and I can foresee that some forward thinking and responsible, employers will consider testing and recording the working environment as part of their Quality Standards routines. Undertaking this would achieve two things: • First, it would identify any correctable element generating undesirable particulate matter, especially if, as is often the case, the company operates particle generating industrial processes in the same building. It makes sense to know the facts and to respond accordingly with preventive measures. • Second, it would give assurance to employees – many of whom suffer minor allergies such as hay fever – the confidence and knowledge that their welfare is being monitored. This can be carried out as a service at intervals by a contractor such as OptiCal or alternatively the latest units are economical to hire or purchase and are easy to use at critical points on a site require for regular periodic checks. If I were an industrial employer I would regard particle analysis of the working environment as important as analysing temperature, humidity, lighting and safety. The health of the individuals in the work force is just as important as the industrial process itself. Returning to human traits, it is a fact that once detailed knowledge emerges a reaction occurs among the informed. The trouble with science is, the bigger the issue, the more difficult it becomes to obtain consensus between theories. In the case of the ozone layer problem, for example, the blame has been placed variously on America's energy consumption, Brazilian forest fires and flatulent sheep in New Zealand, whereas it is probably due to all of these and more. The science of particle counting, however, is precise, available and indisputable in its conclusions. It has a high relevance to our daily lives and its more widespread use in habitat monitoring would appear to be a statistic that could prompt better understanding and control of our everyday environment.