Final answer:
The question pertains to ISO cleanroom standards for Particle Emission Control (PEC) in engineering environments. The ISO classification determines the level of airborne particle cleanliness necessary for various industry-specific applications to prevent contamination.
Step-by-step explanation:
The question appears to be related to cleanroom standards, particularly pertaining to Particle Emission Control (PEC) in an engineering or manufacturing context. The blank in the question 'PECs must be ISO ____ or cleaner' is likely referring to the ISO 14644-1 classification of cleanrooms and associated controlled environments. ISO 14644-1 is an international standard that specifies the classification of air cleanliness in terms of the concentration of airborne particles. For example, 'ISO 5' would denote a cleanroom with a certain maximum allowable particle concentration.
Cleanroom standards are critical for industries where small particles can adversely affect the manufacturing process, such as semiconductor manufacturing, pharmaceuticals, biotechnology, and medical devices. The specific ISO class required for PECs would depend on the industry and the level of cleanliness necessary to protect the product or process from contamination.
Understanding and maintaining the requisite cleanroom standards is essential for product quality and compliance with industry regulations.