Grease collected over a period of time is hard to remove and cleaning by hand means you won’t be able to reach inside the filter, so you’ll only ever be cleaning the surface meaning that they remain an ignition point. If you put the filters in the dishwasher, particles of metal from the filters will shed into your dishwasher and a build up of these metal particles will eventually break your dishwasher. The excessive amount of pure grease contained within the filters means that a film of grease will remain on your dishwasher walls which will then contaminate dishes washed in the machine thereafter. Dishwasher detergent contains aggressive chemical cleaners which will degrade the integrity of the grease filter. Additionally uncontrolled discharge of FOG (Fats, oils and grease) from a food service establishment into the mains drain could contravene Section 111 of the Water Industry Act 1991 and result in the water and sewerage company bringing a prosecution against you with recovery of their costs and a potential fine if proven. Furthermore any in-house cleaning will not be independently recorded as required by your insurance.
TR19 Guidelines state that periodic specialist cleaning of canopies, filters and associated drains and traps in accordance with manufacturers' recommendations is best practice and as the canopy is an area of higher fire risk, consideration should be given to more frequent cleaning in accordance with insurers' requirements.