How a Cooker Hood Works

There are two types of cooker hood available - recirculating and extracting - and these both work in different ways, as outlined below.

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In a recirculating cooker hood, air is typically drawn in by the fan through a carbon filter to reduce smells before being vented back into the kitchen. Steam travels through the cooker hood filter, with most of the moisture being passed straight back into the kitchen.

As a result condensation forms on windows and a higher level of air flow from them is necessary to prevent damp building up. In addition, some moisture is typically left behind in the filters and this may drip if the cooker hood is switched off immediately after venting a lot of steam from a saucepan or fryer.

To prevent this it is important to run the hood for several minutes after you have finished cooking to evaporate the excess moisture. In the case of a hot chip pan, any water that drips into it will instantly boil so also cover any hot oil as a precaution.

These factors are less of an issue with extracting cooker hoods, as the steam is drawn through the hood by the fan and blown out of the kitchen through ducting. While this helps to reduce the amount of condensation within the kitchen, it is important to note that the air drawn out of the room will need to be replaced by air drawn in.

If your home has been thoroughly draft-proofed with no air allowed into it this type of extractor hood will quickly reduce its air flow until it can no longer extract any air, steam or smells.

Something else to consider with extractor hoods is the length, diameter and number of bends of any ductwork for the air to pass through before being vented out of the building. Depending on these factors the air flow can be significantly reduced and, in longer pipework, it may be necessary to add an additional fan in the ductwork to help air flow. In the case of new DIY installations, check the installation guide for information regarding the recommended duct length and size.

If your cooker hood no longer works efficiently but the motor is running and making the same level of noise, you should first check the filters (and replace them, if necessary). It may even be possible to temporarily remove these to confirm the motor is working correctly.

For information on replacing filters see our article "How to Change a Cooker Hood Filter" article

* All information provided is a guide only. BuySpares accepts no liability for any problems occurred while attempting any advice shown. If in any doubt contact a qualified repair service.