Cleanrooms have meticulous levels of contamination (ISO Class) specified by the number of particles per cubic meter at a specified particle size. Air entering a cleanroom from the outside must be filtered to exclude dust. The air inside a cleanroom must be constantly recirculated through high-efficiency particulate air (HEPA) filters to control contaminants that are generated inside the room. Particle levels are tested using a particle counter and microorganisms are detected and counted using environmental monitoring methods.
An overview of good cleanroom design is provided by Juan Miguel Cana Lopez and Kim Zurawski, Grifols, in Controlled Environments magazine.
Here is an extract: “Consideration must also be given to cleanroom features such as nonporous and smooth surfaces, including walls and ceilings that can withstand routine decontamination; proper pressure differentials between rooms, the most positive pressure being in the aseptic processing rooms or areas; use of unidirectional airflow in the immediate vicinity of exposed product or components; sufficient air change frequency; appropriate humidity and temperature environmental controls; and a documented sanitization program.”
Posted by Dr. Tim Sandle