Particulates accumulate in {HEAD ~ the trap} 2 over {TAIL ~ a period} of time, and, the extent of accumulation of the particulates is detected by the pressure sensors 11a and 11b 
over
Particulates accumulate in { HEAD ~ the trap } 2 over { TAIL ~ a period } of time , and , the extent of accumulation of the particulates is detected by the pressure sensors 11a and 11b
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH