Cooker Hoods: Ducted or Recirculating, and How Powerful?

A cooker hood removes steam, grease and smells before they settle on walls and cupboards. Choosing one comes down to three questions: where the air goes, how much air it moves and how wide it is.

Ducted or recirculating?

Type	How it works	Pros	Cons
Ducted (extraction)	Air goes outside through a duct	Removes steam and smells properly	Needs a route to an outside wall or roof
Recirculating	Air passes through grease and charcoal filters, then back into the room	Fits anywhere	Does not remove moisture; charcoal filters need replacing

A slimline extractor hood above a two-burner gas hob, with its duct pipe exposed · Photo: Wu Samkors · CC BY-SA 3.0

How powerful?

A common rule of thumb is that a hood should change the air in the kitchen about 10 times an hour:

room length × width × height (in metres) × 10 = extraction rate in m³/h

Kitchen size	Room volume	Aim for
3 × 3 m, 2.4 m ceiling	21.6 m³	about 220 m³/h
4 × 3.5 m, 2.4 m ceiling	33.6 m³	about 340 m³/h
6 × 4 m open-plan, 2.4 m ceiling	57.6 m³	about 580 m³/h

The legal minimum in England: Approved Document F asks for at least 30 litres a second (108 m³/h) from a cooker hood that extracts outside, or 60 l/s (216 m³/h) where there is no hood or the hood only recirculates. A recirculating hood on its own does not count as ventilation. Look for the noise level in dB on the energy label as well: a hood you avoid using because it is loud does no good.

Size and height

Width: at least as wide as the hob, ideally a little wider.
Height above the hob: follow the hood maker's instructions; if none are given, Approved Document F suggests 650–750 mm for a ducted hood.

In an old fireplace

A range cooker set into a chimney breast often has a hood fitted inside the opening: see inglenooks and chimney breasts and our range cooker guide.

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Frequently asked questions

Does a recirculating cooker hood meet Building Regulations?

Not on its own. Approved Document F says a recirculating hood does not provide compliant ventilation, so a kitchen with one needs a separate extract fan of at least 60 litres a second.

How high should a cooker hood be above the hob?

Follow the hood maker's instructions. If they give no figure, Approved Document F suggests 650–750 mm above the hob for a hood that extracts outside.

Is a bigger extraction rate always better?

Not always. Above what the room needs, a stronger motor mostly adds noise. Size the hood to the room and check the noise level in dB.