Nitrogen dioxide gas is sensed in accordance with a color change before and after {HEAD ~ the sensor element} is exposed to {TAIL ~ air} to be measured for a predetermined time 
is exposed to
Nitrogen dioxide gas is sensed in accordance with a color change before and after { HEAD ~ the sensor element } is exposed to { TAIL ~ air } to be measured for a predetermined time
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH