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