Elements of clean-room technology and contamination control

The heart of the clean room is the high efficiency particualte air (HEPA)/ultra-low penetration air (ULPA) filter, which provides the highest level of air cleaning ever achieved by a single-process step. Filter technology has seen tremendous growth in terms of ultimate performance and air handling capacity. Mere installation of ULPA filters of 99.99995 per cent efficiency for 0.2 mum aerosol is not sufficient for achieving the desired performance of a clean room. Other design aspects like flow fields, face velocity, number of air changes, make-up air fractions and precise control of other environmental parameters (temperature, humidity, airflow, noise, vibrations, electrostatic discharge, etc.) are equally important.