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