Preferably, the moisture may be added to achieve {HEAD ~ a predetermined level} of humidity in {TAIL ~ the selected gas component} 
in
Preferably , the moisture may be added to achieve { HEAD ~ a predetermined level } of humidity in { TAIL ~ the selected gas component }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL