Cleaning out your kitchen exhaust system prevents a seriously dangerous fire hazard from being present. Exhaust systems collect grease and other substances, and when they build up, the extractor may fail, which then reduces the air flow within the kitchen, making it the right type of environment for a fire to start.

Birds also like to build nests in these vents because of the constant warm air coming out of them. 

We Clean them just like we do dryer vents.