Equations for predicting airborne cleanliness in non-unidirectional airflow cleanrooms

Equations are derived in this paper for predicting the airborne concentration of particles and microbe-carrying particles in non-unidirectional airflow cleanrooms during manufacturing. The equations are obtained for a variety of ventilation systems with different configurations for mixing fresh and recirculated air, air filter placements, and number and efficiency of air filters. The variables in the equations are air supply rate, airborne dispersion rate of contamination from machinery and people, surface deposition of particles from air, particle concentration in fresh makeup air, proportion of make-up air, and air filter efficiencies. The equations are amenable to relatively simple modification for the study of different cleanroom ventilation systems. The use of these equations to investigate the effect of different configurations of ventilation systems and the relative importance of the equation variables on airborne concentrations will be reported in a further paper

Calculation of airborne cleanliness and air supply rate for non-unidirectional airflow cleanrooms

Equations have been recently derived by Whyte, Lenegan and Eaton for calculating the airborne concentration of particles and microbe-carrying particles in non-unidirectional airflow cleanrooms. These equations cover a variety of ventilation systems, and contain the variables of air supply rate, airborne dispersion rate of contamination from machinery and people, surface deposition of particles from the air, concentration of contamination in fresh make-up air, proportion of fresh air, and air filter efficiencies. The relative importance of these variables is investigated in this present research paper, with particular regard to the removal efficiency, location, and number of air filters. It was shown that air filters were important in ensuring low levels of contamination in cleanrooms but the types of filters specified in current cleanroom designs were very effective in ensuring a minimal contribution to the cleanroom’s airborne contamination especially when a secondary filter is used in addition to a primary and terminal filter. The most important determinants of airborne contamination were the air supply rate and the dispersion rate of contamination within the cleanroom, with a lesser effect from deposition of airborne particles onto cleanroom surfaces. The information gathered confirmed the usefulness of the equation previously used by Whyte, Whyte, Eaton and Lenegan to calculate the air supply rate required for a specified concentration of airborne contamination

Calculation of air supply rates and concentrations of airborne contamination in non-UDAF cleanrooms

This article reviews a series of scientific articles written by the authors, where the following topics were investigated in relation to non-unidirectional airflow cleanrooms. (1) The air supply rate required to obtain a specified concentration of airborne contamination. (2) The calculation of concentrations of airborne contaminants in different ventilation and dispersion of contamination situations. (3) The decay of airborne contamination (a) during the ‘clean up’ test described in Annex 1 of the EU Guidelines to Good Manufacturing Practice (2008); (b) during the recovery rate test described in Annex B12 of ISO 14644-3 (2005); (c) associated with clean areas, such as airlocks, to reduce airborne contamination before a door into a cleanroom is opened. Worked examples are provided to demonstrate the calculation methods to provide solutions to the above topics

Ensuring the air supply rate to a cleanroom complies with the EU GGMP and ISO 14644-3 recovery rate requirements

The European Union Guidelines to Good Manufacturing Practice (EU GGMP) includes a recommendation for a 'clean-up' of airborne particles in the cleanroom after completion of operations, where the concentration should decay by up to 100, or 10 fold, in 15 to 20 minutes. When designing a ventilation system for non-unidirectional airflow EU GGMP Grade B and C cleanrooms, it is necessary to determine if the proposed air supply rate will be sufficient to provide the air change rate for the clean-up specified in the EU GGMP, and such a method is provided in this article. The air change rates for other decay times and reductions in particle concentrations in cleanrooms can also be calculated by this method

Calculation of airborne cleanliness and air supply rate for non-unidirectional airflow cleanrooms

Equations have been recently derived by Whyte, Lenegan and Eaton for calculating the airborne concentration of particles and microbe-carrying particles in non-unidirectional airflow cleanrooms. These equations cover a variety of ventilation systems, and contain the variables of air supply rate, airborne dispersion rate of contamination from machinery and people, surface deposition of particles from the air, concentration of contamination in fresh make-up air, proportion of fresh air, and air filter efficiencies. The relative importance of these variables is investigated in this present research paper, with particular regard to the removal efficiency, location, and number of air filters. It was shown that air filters were important in ensuring low levels of contamination in cleanrooms but the types of filters specified in current cleanroom designs were very effective in ensuring a minimal contribution to the cleanroom’s airborne contamination especially when a secondary filter is used in addition to a primary and terminal filter. The most important determinants of airborne contamination were the air supply rate and the dispersion rate of contamination within the cleanroom, with a lesser effect from deposition of airborne particles onto cleanroom surfaces. The information gathered confirmed the usefulness of the equation previously used by Whyte, Whyte, Eaton and Lenegan to calculate the air supply rate required for a specified concentration of airborne contamination

Brandausbreitung bei verschiedenen Stoffen, die in lagermaessiger Anordnung gestapelt sind. T. 1 Literaturauswertung

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