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