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Should I get my chimney swept before using my wood burner?

Posted by Trish O'Flynn on 12 December 2016 at 12:30 pm

Is your chimney clean enough for Santa to avoid getting stuck this year? Nobody wants smoke coming back down into the room, so getting the chimney and flue swept to free them of obstructions is a must if you want a safer, more efficient burn this winter.

Whatever fuel you are using, people often use the terms ‘flue’ and ‘chimney’ interchangeably. The flue is the working part of the chimney that takes the combustion gases from your boiler safely to the outside, it may be lined to improve efficiency and eliminate leakage. The chimney includes the shaft which houses one or more flues, but not all flues are placed in chimneys.

The type and location of the flue needs to be decided before your biomass boiler is installed. Mark Howard from Sungift Energy explains: “A certified boiler installer will survey your property and specify the flue (and cowl if needed) that is best for your boiler. They’ll make sure it meets the requirements of the manufacturer (which is important for the warranty) and the Building Regulations.”

Why is it important to clean your chimneys and flues regularly?

Apart from Christmas treats, there are two reasons to sweep the flues serving your solid fuel appliance: efficiency and safety.

Efficient burning relies on the flue taking the combustion gases out of your boiler. The updraught assists the complete combustion of the fuel, reducing smoke and emissions.

“Inefficient burning means a build-up of tar and soot in the flue, which can have a corrosive effect on the appliance and chimney. It also increases the risk of a chimney fire” says Mark Howard.

When it comes to safe operation of your boiler, insufficient draw or obstructions in your flue, such as birds’ nests or other debris, mean that dangerous exhaust gases can come back into the room. Audible carbon monoxide alarms are a legal requirement when installing solid fuel boilers and will keep you and your family safe from the risk of poisoning.

How often should I have my chimney swept?

The chimney should be cleaned before your boiler is installed and after that the frequency of cleaning will depend on the following factors:

  • type and quality of fuel,
  • boiler requirements,
  • type of flue or chimney,
  • how long the appliance is in use.

The Heating Equipment Testing and Approval Scheme (HETAS) recommends the following frequencies when burning different fuel types:

  • wood - at least twice a year
  • authorised smokeless fuels at least once a year

The quality of the fuel is an important factor. Unseasoned wood, for example, produces a lot of soot and tar deposits.

The installation commissioning form you got from your appliance installer should also indicate the recommended frequency of cleaning.

Apart from the flue, you should check the parts of the chimney (brickwork, flashings, terminals) that are open to the weather every year. Soot can build up on a terminal with anti-bird mesh and should be cleaned regularly.

If you have just moved house it makes sense to clean the chimney before using any solid fuel appliances.

If you have had a chimney fire, the chimney and appliance should be checked for damage before you use them again.

How do I choose a chimney sweep?

If you have the skills and equipment you can clean the chimney yourself but your house insurance may require that you use a qualified sweep. The British Flue and Chimney Manufacturers Association (BFCMA) say you should not try a 'controlled' chimney fire or over-firing (allowing the fuel to burn fiercely and out of control) to try and clean the chimney.

All HETAS approved sweeps are members of one of three trade associations, have attended a HETAS training course and have public liability insurance.

How much will it cost?

This will vary according to your location and the complexity of the installation with prices starting from about £45 (excluding VAT) for a straightforward job that takes about 30 minutes.  

What can I expect when my chimney is swept?

Before the sweep arrives you should clear space for them to work, including access to the chimney, and clear the grate. Remove ornaments and anything precious from around the fireplace and mantelpiece. Mince pies and carrots are permitted.

You should check with the sweep the cleaning method they are going to use. The BFCMA recommends mechanical sweeping, with a brush and rod, as it removes not just soot but mortar, birds’ nests and other debris. The brush should pass through the entire length of the chimney (cowl permitting).

Cleaning a flue using chemical chimney cleaners or vacuum cleaning alone is not recommended by the BFCMA. In fact, some chemical cleaners might invalidate your boiler warranty.

A qualified chimney sweep will give you a Certificate of Sweeping and an inspection report when they finish the job.

Find a HETAS approved sweep.


Image credit: FreeVector


1. British Flue and Chimney Manufacturers Association

More information on:

1. Chimneys and linings (HETAS)

 2. Chimney sweep trade associations

3. Carbon monoxide safety

4. Preventing chimney fires (Norfolk Fire and Rescue Service)

5. Carbon monoxide alarms for landlords of private rented properties.

More information about  Biomass Boilers and  Energy Saving and Renewable Energy on YouGen.


About the author: Trish is a web content writer with the National Energy Foundation.

If you have a question about anything in the above blog, please ask it in the comments section below.

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