Regular checks to support a periodic cleaning regimen are prudent as there systems get coated with dust and debris and saturated with oil and fat residues. There have been many fires associated with poor maintenance.

Interesting question! I have never seen general mechanical extraction counted as LEV in a kitchen environment. Extraction hoods are used to provide general ventilation of smells/ heat and the tiny amounts of the by products of combustion. I have seen then tested for efficiency after installation but know of no commercial kitchen that tests them on a 14 month basis. Cleaning and having filters changed on a regular basis is important but as Gas appliances deemed to emit high levels of CO2 are flued rather than relying on overhead extraction I would not expect Gas ovens to have overhead mechanical extraction subject to statutory inspection.

I don't think it is classed as LEV, however, adequate maintenance should be in place.

Speaking as an LA enforcement officer, we do not treat ventilation canopies above kitchen appliances as LEV and therefore do no seek documentary proof of statutory testing. We do, however, check cleaning regimes and view the systems as a possible fire hazard, therefore also advise duty holders to have the ducting professionally cleaned to avoid oil build-up and efficient operation.