Product review (1 stars): Usless.  Poor Engineering.
This hood is poorly designed.  The fan box is not constructed so as to direct the exhaust to the exhaust louvers.  Instead, the air sucked in is reflected back into the fan itself, creating a back pressure which causes the fan to slow down.  As a result most of the cooking steam escapes around the side of the hood rather than passing through the filter.  I would estimate that maybe 10% of the steam actually makes it to the filter.