Flue accessories installed in extractor fans could benefit from professional cleaning now and again, alongside fan blades.
Most components of a common kitchen extractor fan can be cleaned manually by owners - with most models capable of being dismantled and washed with water or in a dishwasher.
While this kind of approach is suitable for charcoal filters and grills, fan blades may require more delicate attention.
Calling in a professional engineer to clean fan blades may be necessary, so it may also be worth asking for flue accessories integral to the fan to be serviced at the same.
This may be particularly necessary if your haven't ever had your fan serviced, or if you cook fatty foods on the hob fairly regularly.
Fat deposits within the flue system or on the fan and filter itself can pose a significant fire hazard, so dealing with the problem early could be the difference between remaining safe or causing a life-threatening fire.