The output signals from transducers and are used by {HEAD ~ data processing unit} to compute the total concentration of hydrocarbon gases and vapors and {TAIL ~ the concentration} of methane gas within cells and  
The output signals from transducers and are used by { HEAD ~ data processing unit } to compute the total concentration of hydrocarbon gases and vapors and { TAIL ~ the concentration } of methane gas within cells and
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH