The selective transmission may be achieved by providing a wall section consisting of a selectively permeable material, chosen to permit {TAIL ~ the transfer} of {HEAD ~ only the gaseous substance} to be monitored between the interior and the exterior of the chamber 
The selective transmission may be achieved by providing a wall section consisting of a selectively permeable material , chosen to permit { TAIL ~ the transfer } of { HEAD ~ only the gaseous substance } to be monitored between the interior and the exterior of the chamber
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH