Cleanrooms are classified according to the number and size of particles permitted per volume of air. The most common standards are set by the International Organization for Standardization (ISO). For example, an ISO 1 cleanroom allows only 12 particles per cubic meter, whereas an ISO 8 cleanroom allows up to 3,520,000 particles per cubic meter. For nanotechnology applications, cleanrooms typically fall within the range of ISO 1 to ISO 5.
