A well-made and well-installed extractor hood in your kitchen can be a tremendous boon for both sanitary and safety reasons. The powerful fans in the hood extract airborne grease, smoke and other particulate matter from your kitchen, while its position above your stove top allows it to assist in suppressing and putting out grease fires.

However, any extractor hood is only as good as the ventilation system it is attached to--after all, all the air your hood extracts and cleans has to go somewhere. As such, the type of ventilation your hood will use is one of the first decisions you should make, as different types of ventilation will perform differently under different circumstances. You have two main types of ventilation systems to choose from--external ventilation or recirculation.

What are the pros and cons of choosing external ventilation?

Choosing an externally vented extractor hood comes with a range of advantages over recirculating models:

• Thorough air cleaning: Extractors hoods with external ventilation vent their air they suck up directly to the outdoors, so they can be relied upon to thoroughly remove airborne grease and contaminants from your kitchen.
• Filter-free: This external ventilation precludes the need for air filters found in recirculating extractor hoods, sidestepping the unpleasantly messy task of cleaning and/or replacing your hood filters.
• Power efficiency: Since externally vented hoods do not require fans to reintroduce cleaned air back into your kitchen, they are generally cheaper to run over the long term than recirculating hoods.

However, there are also a few disadvantages that you'll have to deal with:

• Noise: The ductwork connected to an externally venting hood can function as an echo chamber of sorts and dramatically increase the noise your hood generates, particularly if the duct is overly spacious or is lined with ageing materials.
• Difficulty of installation: If suitable ducting is not already present when you you come to install an externally venting hood, you will have to create one. You can construct small ducts yourself, but larger or more complicated ducts should always be installed professionally to prevent structural damage. You will also have to ensure that the hood's ducts vent to the outdoors, rather than a crawlspace, basement or loft.

What are the pros and cons of choosing a recirculating extractor hood?

These types of hoods are generally more complicated in form and function, but this added complexity comes with some distinct advantages:

• No ducting or ventilation required: Recirculating extractor hoods clean kitchen air of airborne contaminants using charcoal-filled cartridges before returning the cleaned air to the kitchen, rather than venting dirty air outside. This precludes the need for complicated and expensive ductwork installation, and  it significantly simplifies the installation process. It also means that hoods can be installed simply in kitchens that do not have easy external access, such as those found in high-rise apartments or basement properties.
• Low installation costs: Without the need to install ducts, recirculating hoods are subsequently much cheaper and faster to installed than externally venting models, and DIY-savvy home owners should be able to tackle installation themselves.  

They do, however, come with a number of drawbacks:

• Filtration quality: While modern recirculating hoods extract the vast majority of airborne contaminants from the air, they are not as efficient as externally venting models, and may not be up to scratch for people who suffer from sensitive food allergies or respiratory problems.
• Filter changes: Changing the filters in a recirculating hood frequently is vital to preserve proper functioning, and should be done regularly. Replacement filter cartridges can be relatively expensive, and may be difficult to find if you choose a lesser-known hood manufacturer.