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Safety Advice

It is commonly believed that only gas appliances produce carbon monoxide. All appliances that burn fuel produce carbon monoxide your solid fuel stove or open fire produce 100’s of times that of gas or oil appliances. This, and the risk of a chimney fire, is why it is important to have your chimney swept by a trained and competent person, after all no one wants to become a number on next year’s carbon monoxide or fire statistics. The number of chimney fires is increasing every year in the UK with as many as 32,000 homes in the a UK having a chimney fire in 2010. A significant number will be largely due to not getting the chimney swept often enough.

Other contributing factors are:

  • Burning fuel that is inappropriate for the appliance.
  • Burning fuel with too high a moisture content (logs should be less than 20% water).
  • Overnight burning / slumbering fire – please don’t do this, it can be dangerous and costly and is highly polluting.
  • Unsuitable or inefficient stove or chimney.

A NACS Chimney Sweep will be able to provide you with good basic information on the use of your appliance and fuel. This advice may well save you the cost of their visit in fuel savings each and every year.

Some Insurance companies will no longer pay out for chimney fire damage unless the flue has been swept and maintained by a professional chimney sweep who can issue a valid certificate of sweeping recognised by the insurance companies themselves. NACS sweeps are required to issue these certificates for every chimney cleaned.  Also, if the fire brigade is called out due to a chimney fire and it is proven that the chimney has not been maintained the local council can bill you for the call out, and this has been known to be up to £2000 per fire crew.

If your chimney is clean it will not catch fire (there is nothing in it to burn!) A NACS sweep has been trained and educated to clean and inspect your solid fuel appliance and flue. They will also be able to recommend any repairs needed, recording them on your sweeping certificate. We recommend that you call a NACS certified sweep, since they have passed their assessment and their understanding of the complexities of chimney and venting systems is vast.

Sweeping frequency:

  • Smokeless coals: At least once a year (Often believed to not need cleaning)
  • Wood: Once a season when in use on open fires, twice a season for stoves
  • Bitumous coal: Twice a year
  • Oil: Once a year
  • Gas: Once a year


Fuels: Correct Fuel, Correct Use

It is very important to burn the correct fuels on your solid fuel appliance to both keep it and the flue in good condition and to get the most efficient use from it.

Make sure the liner fitted is suitable for the fuel you want to burn or that the fuel is suitable for existing liners. Using the wrong type of fuel on a liner will reduce the life of the liner considerably due to increased corrosion. This can create a dangerous situation. The liner life may be reduced to as little as 3 years if the correct fuel is not used.

The flue will soot up at a vastly increased rate if the right fuel for the appliance is not used. This is due to the reduced efficiency of the appliance. Using the wrong fuel will also increase the sweeping frequency required to maintain a safe level of soot in the flue / chimney.

Burning coal or smokeless fuel in a wood burner will produce very little heat but lots of soot due to the appliance not being designed for that fuel. Wood burning on an open fire will give very little heat for a lot of fuel consumed and high fuel consumption leads to more build up of soot or tar.

Suitable seasoned timber must be used in all solid fuel stoves. No man made wood such as MDF, ply board and chip board should be burnt. Failure to do so will result in low heat output and a build up of tar in the flue / chimney. Tar in chimneys is very flammable and carries a very high risk of chimney fire. Removing this tar is a very specialist job and can cost a lot of money due to it not being removable by normal BS6461 methods. It is usually easier to remove the liner and fit another if this build up is too severe as damage to the liner is very likely to be caused during the process.

Beware of the word seasoning. Many retailers sell seasoned wood. The only thing that matters is the moisture content and this should be less than 20%

Wood storage is very important; it needs to be kept in a dry store that lets the air get round it – stack it don’t pile it up. Good ventilation is more important than keeping the rain off. Correctly stacked logs will continue to lose internal moisture even if they are rained on from time to time. That said the best store will have a roof to keep rain off.

If the wood is not kept aired then it will start to rot meaning it will not burn fully and have a reduced calorific value.



It is very important to let you solid fuel appliance breath properly or the flue will be unable to take away the fumes effectively which will lead to smoking back or slow gas speed meaning that the flue will soot up quicker. Insufficient air flow will also lead to incomplete combustion, low levels of heat output and increased pollution.

Ventilation requirements

Open fires

In the case of an open fire with or without boiler an air opening or openings with a total free area of at least 50 per cent of the throat opening area should be provided, this is usually 16,500mm2 for a typical open fire. This is ventilation to the room from outside the building.

Stoves and room heaters

Houses built before 2008 have a 5KW size allowance without the need for a vent. If the stove is bigger than 5KW a vent must be fitted. The vent needs to be 550mm2 per KW over 5KW this means an 8KW stove would need a vent of 1,650mm2.

If the house is built after 2008 then a vent needs to be fitted that is 550mm2 per KW so an 8KW stove in a new build would need a vent of 4,400mm2

NOTE: It is sometimes necessary to fit a vent in an older property with a 5KW stove if there is not sufficient air flow.

Your NACS sweep will be able to advise you on your ventilation requirements.


Fire Safety

UK fire statistics show that each year on average over 31,000 houses have chimney fires. Around 9,500 of these cause damage to the property and great inconvenience to the home owner and their family.

This will be due in a large part to not getting the chimney swept often enough or burning fuel that is inappropriate for the appliance and causing tar to build up in the chimney. Badly installed appliances can also cause chimney fires, a NACS sweep will be able to point out any problems with your installation if there is any.

As most insurance companies will no longer pay out for claims made due to chimney fires unless the chimney has been swept by a professional chimney sweep and a valid certificate of sweeping issued that is recognised by insurance companies, it is especially important to make sure it does not happen to you. It is bad enough being an entry on the UK fire statistics but even worse if the insurance does not cover the bill.


To help prevent chimney fires

Chimney fires can burn explosively – noisy and dramatic enough to be detected by neighbours or passers-by. Flames or dense smoke may shoot from the top of the chimney. Homeowners report being startled by a low rumbling sound that reminds them of a freight train or a low flying airplane. These types of fire will most likely cause damage. This damage may not be apparent and everything may seem fine. Do not use the appliance / chimney until a full survey has been carried out and a report produced (this applies even more to steel chimney systems).

These, however, are only the chimney fires you know about. Slow-burning chimney fires don’t get enough air or have enough fuel to be as dramatic or visible as their more spectacular cousins but the temperatures they reach are very high. This can cause damage to the chimney structure and nearby combustible parts of the house.

Chimney fires don’t have to happen. Here are some ways to avoid them:

  • Use seasoned woods only (dryness is more important than hard wood versus soft wood considerations) many suppliers also sell sawdust logs and other log substitutes that will help keep your chimney cleaner. We advise using logs with a water content of less than 20%.
  • Build smaller, hotter fires that burn more completely.
  • Never burn cardboard boxes, waste paper or Christmas trees; these can start a chimney fire as bits from them can get sucked up the flue and set fire to soot in the chimney.
  • Burn Recommended fuels ONLY and NEVER use your fire as a waste paper bin. It has been proven that this practice starts chimney fires and produces toxic chemicals.
  • Use only recommended fuels for your appliance and flue type (If you are unsure check your manufactures instruction or ask your stove supplier). Your local fuel merchant may also be able to give you advice.
  • Extra information is available from insurance companies if you have a thatch property and it is very important to follow your insurance companies’ recommendations.

To help prevent chimney fires

  • Comply with building regulations and to make sure that the person undertaking the work is competent to undertake such work. Lining chimneys in thatch properties is very specialist work. Make sure your engineer knows of the differences in the regulations for installations in thatched properties and those properties with non-combustible roof materials.
  • The best way to install a chimney liner into any chimney is to use the proper liner for the fuel type that the liner is serving. It is recommended that a HETAS registered engineer carries out the work.
  • Make sure that you have a regular sweeping programme in place with a sweep who is trained and registered and can issue you with certificates.
  • For the liner to be supported properly to keep it away from the sides of the chimney.
  • For the register plate and supports for same to be made from non-combustible material, preferably metal, and be held in place with suitable fixing such as raw bolts, not plastic plugs that will melt in the event of a fire.
  • For the whole void of the chimney to be in filled with non-combustible insulative material (micro fill or similar) or be well vented in accordance with the manufactures instructions.
  • For the liner to be finished off within the chimney as per manufacturers recommendations.
  • Remember that when a liner is fitted it should be easily accessible in order for it to be swept regularly. All NACS sweeps are required to carry equipment to clean metal liners as a requirement of their assessment and membership.
  • The liner should not have a spark guard or any cowl type fitted unless it is cleaned regularly. Please consult with your insurance company.

Make sure you are aware of the frequency that your chimney must be swept in order to comply with your insurance policy. Your NACS sweep may advise a more regular sweeping frequency than your insurance company requires depending on your situation and what they find in your chimney.



Damaged Chimneys – stacks, liners, etc.

The two main reasons for damage to a chimney stack are,

  • A chimney fire (see fire safety)
  • Weathering with age.

A chimney is built in the most exposed part of the house, sun, wind, rain and frost it weathers it all for years, and then we light fires under it and fill it full of corrosive soot that eats away at it from the inside. It is no wonder that it needs maintenance from time to time.

The chimney’s other big problem is that it is built on top of the house where the home owner does not look at it. Only when things go wrong with it does it get looked at, by this time the damage is more advanced than it needs to be, having not been inspected regularly. Your local NACS sweep will always check your stack (usually with binoculars) before sweeping the flue to make sure it is sound and that no further damage is caused.

Damage to the chimney stack and flue can affect the performance of your chimney and reduce its ability to remove the harmful gasses that the appliance produced, flue damage can also create leaks into the bedroom and loft area of the house which can result in injury or death in extreme cases, this is why we recommend that a full survey is carried out on the installation and flue before it is used again after a known chimney fire.

Fire and weather damage to the stack also has the additional problem that falling masonry from high can cause large scale damage to property and injury or death to residents or passers-by. This problem will not arise if your chimney is swept annually by a NACS sweep due to regular inspections and repair recommendations. It is worth keeping on top of these repairs as insurance companies will not pay out for large scale wear and tear repair bills.


Barkers Chimney Sweep