Cooker Extractor fan, more noise than extraction

Cooker hood with extractor fan but there doesn't seem to be much extraction.
The motor is similar to one of these:
https://www.luxairhoods.com/cooker-hood-filters-spares-parts/cooker-hood-motors
There are three filter sections to the hood and if I hold them up to the light I can see quite clearly through them all but if I put a small tissue against even on full it will barely hold.
If I wet my finger and put it near the motor it almost feels as if more air is on the motor side pushing out than on the other side of my finger being drawn in. Yet the flap on the extractor exit outside does open so somethings getting out.
Are they inherently inefficient? Or am I expecting too much? Any clues to actually get kitchen smells to exit?
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AnthonyL

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On Wednesday, 15 August 2018 18:20:26 UTC+1, AnthonyL wrote:

The velocity of the air in the duct changes with the cross sectional area. So if the duct is small the flow will be more easily detected.
Air needs to get into the room to replace that extracted, ideally over the top of the hob. If it can't, there will be no extraction.
The filters are intended to catch fat so there is reduced build up in the ducts which might catch fire.
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Expecting too much. Has to be a pressure difference if the flap opens I would have thought. Maybe there is another route for the air to take from where the smell is generated and its being diverted that way. I could never get a cooker hood to do anything. Don't have one any more, mind you its only me here now so nobody to annoy with smelly fish etc! Brian
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Mine goes off with a hell of a bang and given that its in the outside wall, it does suck a lot of air out of the room.

Mine works very well.

I mostly use it when grilling steaks.

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