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