{HEAD ~ Commercially available sensors} which determine {TAIL ~ the type} of gas include depleting or non depleting sensors 
determine
{ HEAD ~ Commercially available sensors } which determine { TAIL ~ the type } of gas include depleting or non depleting sensors
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH