The function of a hood range filter is to capture any grease that passes through the exhaust fan filters of a stove hood. As a hood range filter performs its function, the amount of grease on its surface builds up, making it lose effectiveness over a period of time.
A dirty hood range filter can be cleaned by using a combination of boiling water, de-greasing dish soap and baking soda. As of 2015, certain types of range hood filters can also be washed in a dishwasher, though manual cleaning is recommended beforehand. An article on The Kithcn recommends that a greasy range hood filter be cleaned at least once every month.