A method 1 wherein {HEAD ~ the oxygen content} of {TAIL ~ the gas} is from about 1% to about 100% 
of
A method 1 wherein { HEAD ~ the oxygen content } of { TAIL ~ the gas } is from about 1 % to about 100 %
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH