BoilerFaultCodesYour boiler has detected a safety issue with how it clears exhaust fumes, causing it to shut down to prevent dangerous gases from entering your home.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: Air flow fault (RSF). Flue gas spillage (OF)
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that exhaust fumes are not being expelled correctly through the flue pipe to the outside. The most common reason is a mechanical failure of the fan or a blockage in the air pressure tubes, which prevents the boiler from confirming it is safe to ignite. Because the system cannot ensure toxic gases are being cleared, it shuts down immediately as a protective measure.
This fault can be more frequent during periods of high winds, which can create back-pressure in the flue and interfere with the air pressure switch readings.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like Domestic hot water demand indicator FLASHING FAST (five times per second) — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch 24/28CDi II RSF is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.