Selection Method of Measuring Points for Cleanliness Recovery Test in Non-Unidirectional Cleanrooms

Abstract

Measurement of cleanliness recovery performance in non-unidirectional cleanrooms is described in ISO14644-3 (2005). However, evaluated results sometimes differ due to the selection of measuring points. In this work, the method to select proper points to perform the cleanliness recovery test was proposed. Distribution of airflow and local ventilation efficiency in various types of cleanrooms were simulated using CFD technique, and the relationship between local airflow speed and SVE3 (the 3rd. Scale for Ventilation Efficiency) was studied. As a result, proper evaluation was achieved when the measuring points at which airflow speed did not exceed 20% of supply air velocity were selected. Through study of various types of cleanrooms, this method was found to be applicable to most types of non-unidirectional cleanrooms, but not applicable to vector flow cleanrooms.