Clean Processing Environments
A wide range of manufacturing processes and scientific research facilities require environments where a low level of contamination or pollutants are present, which could otherwise adversely affect the product or research process. These environments are known as cleanrooms, where contamination or pollutants are controlled to a specified “cleanliness” classification standard. The cleanroom classification standards for the UK are laid down in the European Standard BS EN ISO 14644-1 which dictates the requirement for specific particle count measurements and calculations to classify the cleanliness level of a cleanroom or clean area. The classifications range from ISO Class 1 (highest classification) to ISO Class 9 (lowest classification), which specify the number of particles (usually specified at a particle size of 0.1 µm or 0,5 µm) permitted per cubic metre of air.
The cleanroom is designed to control the level of pollutants which may be present in the form of dust, airborne microbes, aerosol particles and chemical vapours. Particulate control is typically achieved by recirculation of air which has been passed through High Efficiency Particulate Air (HEPA) or Ultra Low Particulate Air (ULPA) filters which are used to trap and retain particles larger than the specified size dictated by the cleanroom classification. The number of air changes required through the cleanroom typically rises as the cleanliness class becomes more stringent. The air can be moved through the cleanroom either in a turbulent (multidirectional) or laminar (unidirectional) manner, with air usually supplied from ceiling level and then recirculated either through the floor of the cleanroom or if the cleanroom classification permits, via low level sidewall return grilles.
The control of pollutants inherently involves the requirement for personnel within the cleanroom to comply with a gowning procedure which involves all occupants wearing a combination of gowns, hairnets, masks, clean shoes/boots and even breathing apparatus. Restrictions are also typically placed on the introduction of items into the cleanroom which could generate harmful particulate into the cleanroom environment, for example wood or paper.
The size and configuration of the cleanroom can vary, but can be adopted in industries such as pharmaceutical research and production, biotechnology, medical devices, life sciences and semiconductor manufacture. In tandem with the need to control particulate, it is often a requirement to provide close control of the temperature, pressure and humidity conditions within the cleanroom. Cleanroom temperature and humidity tolerances can be controlled to +/-1oC and +/-5%RH respectively, should the process or environmental conditions dictate this is required. A cleanroom will inherently have a requirement to maintain a suitable pressure regime to minimise the introduction of pollutants/particulate from the outside environment. Where multiple clean areas are being provided, it would be typical to provide a pressure cascade, where the highest classification areas are kept at the highest pressure relative to the outside world, with pressurisation air then being allowed to spill to cleanroom areas of a lower classification, e.g. personnel change areas or cleanroom equipment support aisles. The pressurisation regime ensures the integrity of the cleanroom with respect to the introduction of pollutants and particulate from the outside environment.
The successful design of cleanroom environments therefore requires specialist knowledge to ensure that the associated air handling, cooling, heating, humidification and dehumidification plant are all designed appropriately, taking into consideration the climate local to the cleanroom and the sensible and latent heat gains presented to the cleanroom by the equipment and any occupants. The Directors of Callidus Design Limited have a extensive track record in this field. All are former employees of M&E design consultancies specialising in this sector.
Some examples of our cleanroom design experience can be seen in these examples from our project profile section of this website.
Please get in touch if Callidus Design can be of assistance with the design of your new cleanroom facility.