Normally a hood filter is good for 4 - 6 months, depending on usage and types of cooking.
The filter should not be cleaned but should be replaced at the end of its service life.
This could be due to a problem with the motor or the hood filter getting clogged up.
The amount of smoke extraction depends the cooking method. For methods with high heat e.g. deep frying or wok-frying, the percentage is approx. 30%. For boiling, the percentage can go up to 70%.