Method and {HEAD ~ system} for detecting {TAIL ~ one or more gases} or gas mixtures and for measuring the concentration of one or more gases or gas mixtures 
for detecting
Method and { HEAD ~ system } for detecting { TAIL ~ one or more gases } or gas mixtures and for measuring the concentration of one or more gases or gas mixtures
OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH