Combining coalescing and activated carbon filters in series provides clean, oil free air by removing both oil aerosols and vapors in pneumatic control systems. Note: The air supply to this filter combination must be from a properly broken-in-air compressor producing less than 6 ppm aerosol oil (as measured by a Johnson Controls® A-4000-120 Oil Indicator on the compressor tank outlet) and must also pass through a properly operating air dryer.