This document discusses the design and operation of clean rooms. It defines clean rooms and aseptic areas as spaces with controlled particulate and microbial contamination to reduce product contamination. The main sources of contamination are the atmosphere, operators, working surfaces, equipment, and raw materials. Clean rooms are classified based on particle counts, with Class 100 allowing fewer than 100 particles per cubic foot above 0.5 microns. Proper air flow design via conventional, unidirectional laminar, or isolator systems controls contamination. High-efficiency particulate air and ultra-low particulate air filters are used to filter air entering the clean room.