BoilerFaultCodes AL 01 Emergency
Boiler Fault Code AL 01
Also written as AL01 — same fault.
Reviewed by the BoilerFaultCodes Editorial Team Last reviewed
Fault code AL 01 appears across 1 boiler brand and 13 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.
Most common meaning Your boiler has detected that dangerous exhaust gases are not being cleared safely through the chimney, causing it to shut down to prevent carbon monoxide from entering your home. (As reported on Sime Ecomfort System Plus HE EV)
Pick your boiler brand for the AL 01 fix
Source
Information for the AL 01 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026