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