Cooker Hoods

Cooker hoods are used to extract airborne grease, steam and cooking odours from a kitchen to make them more comfortable to work in. Cooker hoods are available in various styles in different sizes to suit different hobs and from hidden integrated hoods to designer hoods that are designed to be.

Most cooker hoods can be installed to either extract air to outside of the building or to recirculated the air within – which is used can depend upon the distance to the outside of the building and also personal choice.

Air extraction to outside

Cooker hood extractionA Cooker Hood which extracts the air to the outside operates more efficiently than one that recirculates the air as a carbon filter (which removed the odours) is not needed – with an extracting Cooker Hood, only a grease filter is necessary. However the heat in the expelled air is lost to the building and needs to be replaced by cold air drawn in – in cold weather this will increase heating bills but in hot weather it can provide desired cooling.

The Cooker Hood needs ducting to transfer the air to an outside grill, the maximum length of ducting is limited, typically 3 metres is the maximum length of ducting which can be used but this will be reduced by each bend in the ducting run.  

Installation is more complicated than a recirculation hood as the ducting needs to pass through the structure of the building.

Air recirculation into kitchen

Cooker hood recirculationWhere a Cooker Hood is used recirculation mode, both a grease and charcoal filters are needed to remove the grease, steam and odours from the vapours from the hob.

The charcoal filter removes the smell from the air and the air is passed back into the kitchen.

The heat in the air is not lost to the building – this is probably desirable in cold weather although in hot weather it can make using the kitchen uncomfortable.

The filters

The grease filter

Grease filters are fitted to all extractor hoods, they are generally visible when looking underneath. They are usually made of aluminium, stainless steel, ceramic or a fleece material.

Grease filters need to be cleaned/replaced regularly – the frequency depends on usage but typically every 4 to 8 weeks for metal or ceramic filters – fleece filters are disposable and will need to be replaced about every 8 weeks. Some Cooker Hoods incorporate a saturation indicator which shows when a filter needs to be cleaned or changed.

Metal and ceramic filters should just be removed and cleaned – most are dishwasher proof which can make the job easier.

Replacement fleece filters are available from the cooker hood manufacturer – before purchasing a cooker hood which uses fleece filters, check that your supplier can supply replacement fleece filters or that they are available elsewhere locally; always be specific about the size and type of filter you need – there is nothing standard about them.

Charcoal filters

Charcoal filter are fitted to recirculating cooker hoods to remove the cooking odours, they are positioned above the grease filter so that the air passing through them is free of grease.

Charcoal filters cannot be cleaned but need to be replaced about every 9 to 12 months, but this does depend upon the usage of the cooker. Like fleece grease filters, this are not standard so always make sure replacements are available.

Cooker hood fan speed

Most cooker hoods have adjustable extraction rates (fan speed) which can be selected by switches on the hood, this may be just two speeds (high and low) or more.

The extraction rate is important as it should be able to move 10 times the air volume in the kitchen every hour. To calculate this, calculate the volume of the kitchen in cubic metres (length x width x height) and multiply that by 10, this gives the extraction rate per hour required. A cooker should have the maximum extraction rate quoted.


Cooker hoods generally have halogen or incandescent lights on the underside to illuminate the hob witch a switch on the hood.

Getting at the bulbs when one fails can be awkward depending upon the model.


The noise of the fan in the cooker hood can sometimes be intrusive especially when set to a  high speed, most hoods specify the noise in dBA, this should be for the highest fan speed and the lower the number the quieter.

If a cooker hood is switched on for a few minutes before starting to cook, the air will begin to circulate and a lower speed may be all that is required whilst cooking – beginning to cook without the extraction and only switch it on once steam and heat have built up will need a higher speed to clean it.

Installing a cooker hood

Being an electrical appliance in a kitchen Part P of the Building Regulations apply in England and Wales - a kitchen is a “special area” as defined by the Building Regulations.

Under this regulation the local authority do not need to be notified if a replacement cooker hood is being fitted or a new cooker hood installed which uses an existing power supply.

However, if a new power supply needs to be installed, Part P of the Building Regulations requires that the Local Authority Building Control office is notified unless the installation is carried out by a suitably certified electrician.

Style of Cooker Hoods

Although there are a number of cooker hood styles, when deciding which is appropriate for a kitchen, the size of hob needs to be considered as well as the look of the hood. An integrated cooker hood is ideal for a small, 4 ring hob but would be unsuitable for a large range. Ideally the lower face of the hood should be roughly the same width as the cooking area and extend out at least three quarters of the cooking area.

Integrated hoods

An Integrated cooker hood is the most discreet style as it fits behind a door panel above the hob and looks, from the front, just like another wall unit. If the wall behind the hob has other wall units, the cooker hood can just blend in with the run of units.

To operate the cooker hood, the front panel is just pulled out over the hob.

Conventional or visor hoods

A Conventional hood (or visor hood) is usually fitted under a bridging wall unit so that the hood is seen as part of the run of wall units. These cooker hoods are visible and are not hidden behind any casing or false door.

Chimney hoods

Chimney hoods come in many different shapes and sizes but are usually made from highly polished stainless steel sweeping in from a wide and deep lower end over the hob to a fairly narrow upper section which forms a chimney – hence the name. They are very visible and work well especially with wall units on each side.

Designer hoods

Designer cooker hoods are intended to give the ‘wow factor’. Although underneath they are just a cooker hood, they are designed to make a style statement in a kitchen – but whether they fit in with a kitchen design depends on the underling design of the kitchen – one would probably look out of place in a ‘country farm house’ type of style.

Island hoods

Island cooker hoods are specifically designed to fit to the ceiling above a hob built into island units in a kitchen. The hoods are designed so that they can be viewed from all angles around the island.