{TAIL ~ The unburned particulate accumulation} in the exhaust duct of {HEAD ~ a combustion system}, such as the flue lining of a stove, is monitored by a circuit which receives a temperature indicating signal from a temperature sensing device mounted within the duct 
{ TAIL ~ The unburned particulate accumulation } in the exhaust duct of { HEAD ~ a combustion system } , such as the flue lining of a stove , is monitored by a circuit which receives a temperature indicating signal from a temperature sensing device mounted within the duct
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