Gas system contamination monitor - esp for monitoring traces of oil in compressed air lines

Device consists of a narrow linear branch attached to flow system, with inlet and outlet at opposite ends, through which gas from system can be vented. Colouring agent is provided near inlet to dye the contaminants, and adsorbant is packed in the narrow passage, the flow rate of gas through passage being maintained at a predetermined level by needle valve, the flow rate and pressure drop being sufficiently high to allow rapid expansion of gas, with sufficient turbulence to cause agglomeration of the impurities, allow them to become coloured, and then be retained on adsorbant, the progressive colouring along the length of the passage being observed.