Emergency
C33 on Baxi Suprima 40

Your boiler is having trouble sensing the correct airflow through the flue, which safely prevents the boiler from starting to avoid dangerous gas buildup.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Flue Types

From this model's manual
Verified against the Baxi Suprima 40 installation & service manual, page 7.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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