Except for acting as paths of hydrogen, the filtering rod 308 also has {HEAD ~ the function} of filtering impurities and {TAIL ~ other gases} 
of filtering
Except for acting as paths of hydrogen , the filtering rod 308 also has { HEAD ~ the function } of filtering impurities and { TAIL ~ other gases }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL