Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 91·B.12
Corrosion resistance classes
Corrosion resistance classes for chimneys and flue systems are categorized as 1, 2, or 3 based on the type of fuel being burned, with different sulphur content thresholds for gaseous and liquid fuels.
Corrosion resistance classes are set out in Table B3 – this is fuel dependant and expressed as 1, 2 or 3.
Table B3 Corrosion resistance classes (from BS EN 1443)
Corrosion resistance class 1
Possible fuel types
gas: Natural gas L + H
liquid: kerosene: sulphur-content ≤ 50 mg/m³; oil: sulphur-content ≤ 0.2 mass %
wood: —
coal: —
peat: —
Corrosion resistance class 2
Possible fuel types
gas: Natural gas L + H; gas: sulphur content ≤ 50 mg/m³
liquid: kerosene: sulphur-content ≥ 50 mg/m³; oil: sulphur-content > 0.2 mass %
wood: wood in open fire places
coal: —
peat: —
Corrosion resistance class 3
Possible fuel types
gas: Natural gas L + H
liquid: kerosene: sulphur-content ≥ 50 mg/m³; oil: sulphur-content > 0.2 mass %
wood: wood in closed stoves
coal: coal
peat: peat
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