Apparatus for monitoring {HEAD ~ the accumulation} of {TAIL ~ particulates} on the lining of an exhaust duct or the like for a combustion device, comprising: 
Apparatus for monitoring { HEAD ~ the accumulation } of { TAIL ~ particulates } on the lining of an exhaust duct or the like for a combustion device , comprising :
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 OTH OTH OTH OTH OTH