BoilerFaultCodesIntergas F018 Fault Code
The Intergas F018 fault code means: your boiler is struggling to breathe because the pipes that take exhaust gases away or bring fresh air in are restricted or blocked.. It appears on 5 Intergas models in our database.
Technical description: Flue and/or air supply duct is blocked.
What causes the Intergas F018 fault?
This fault occurs when the boiler's internal safety sensors detect that air cannot flow freely into the unit or exhaust gases cannot exit through the flue pipe. The most common reasons are a physical blockage in the external pipework, such as debris or a bird's nest, or a mechanical failure of the fan which is responsible for pushing these gases out.
This fault is more common during the autumn and winter months, as fallen leaves or heavy snow can physically obstruct the external flue terminal.
DIY fix possible
Check the external flue terminal on your outside wall for obstructions like bird nests, leaves, or debris.Ensure there are no items like garden furniture or storage boxes blocking the flue outlet.Clear any heavy snow or ice buildup from the end of the flue pipe.Reset the boiler once to see if the fault clears after removing external obstructions.
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Gas Safe Register →Intergas models that show the F018 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Intergas F018 fault code information on this page is sourced and cross-checked against the official Intergas service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026