Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 77·5.25
Flues for appliances burning Class D (Gas oil) fuel
Flues serving gas oil appliances must be made of acid-resistant materials meeting specific flue designations depending on whether the appliance is condensing or non-condensing.
A flue serving an appliance burning Class D (Gas oil) fuel should be made of materials which are resistant to the acids of sulphur, i.e. minimum flue designation 'D2' for non-condensing appliances or 'W2' for condensing appliances, according to the designation system in BS EN 1443 and related flue standards.
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