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