means for attenuating high frequency electrical signals and for blocking {HEAD ~ the passage} of {TAIL ~ gas} through the passageway, said means including 
of
means for attenuating high frequency electrical signals and for blocking { HEAD ~ the passage } of { TAIL ~ gas } through the passageway , said means including
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH