Each of the sections is separated by a retainer ring having an opening therein smaller in {HEAD ~ area} than {TAIL ~ the area} of the next preceeding scrubber chamber 
than
Each of the sections is separated by a retainer ring having an opening therein smaller in { HEAD ~ area } than { TAIL ~ the area } of the next preceeding scrubber chamber
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH