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