means for generating an electrical signal correlated to the duration of time that said temperature is within a first temperature range wherein {HEAD ~ particulates} accumulate on {TAIL ~ said lining}; and 
accumulate on
means for generating an electrical signal correlated to the duration of time that said temperature is within a first temperature range wherein { HEAD ~ particulates } accumulate on { TAIL ~ said lining } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH