Answer: Pre-filters are generally used downstream of compressors (aftercoolers) and are not very demanding in their use.
Primary filters are generally used for tools, electric motors, cylinders, etc.
Fine filters are generally used for painting, injection molding, instruments, control valves, transmissions, stirring, electronic component manufacturing, nitrogen separation, etc.
Activated carbon filters are generally used in food and pharmaceutical manufacturing, breathing air, gas processing, etc.