You need to periodically clean your over-the-stove vent hood. The thin, silvery screen is the grease filter (there may be more than one). It traps airborne oils and grease to keep them out of the blower and exhaust vent. To clean the filter, remove it and soak it in a degreasing solution until the grease is dissolved. Next, wash it with warm, soapy water to remove any traces of the degreaser. Then put it in the upper rack of the dishwasher and run it through a normal cycle.
Note… If your unit circulates the air rather than vents it, it may have one or more activated charcoal filters. Don't wash these. Just replace them when they lose their effectiveness.
Warning! Be sure the unit is turned off before you clean it. Also avoid spraying cleaner directly onto the light bulb or light bulb socket.
Clean the interior of the vent hood with a standard household degreaser/cleaner.
Clean the exterior of your vent hood with a degreaser/cleaner or a non-abrasive cleanser.
Most vent hood fan motors don't need any maintenance. Over time, the motor and bearings may become stiff because of the constant heat, humidity, and grease to which they're subjected.
Also over time, the blower wheel gets greasy and dirty, which can slow down the fan or cause vibration. Remove the wheel and clean it with a degreaser. Then, if the fan is still slow or if it vibrates, you need to replace the fan motor.
If your fan vents (rather than just circulates), you need to regularly check the vent that leads from the vent hood to the outside, to make sure that grease isn't building-up on the inside of it. If it is, contact a vent-cleaning contractor to clean the vent properly. (You may find such a contractor under "chimney sweeps," or "HVAC duct cleaning," or "ventilation cleaning" in your telephone book Yellow Pages.)