WELCOME TO CASTLE CHIMNEY SWEEPS A National Association of Chimney Sweeps Master Member
WELCOME TO CASTLE CHIMNEY SWEEPS A National Association of Chimney Sweeps Master Member

Questions, Facts, Misnomers and "Old Wives" Tales

Whenever I have conversations involving open fires, stoves, chimneys or sweeping generally, similar questions, misnomers and "old wives tales " usually emerge, some of which are amusing others potentially dangerous. The information below is intended to address some of the more common issues and themes.

Do you have to be qualified to sweep chimneys?

Unfortunately not. Chimney sweeping is currently an unregulated industry. Anyone can buy a set of drain rods, a brush and a domestic vacuum cleaner and legally call themselves a chimney sweep and I have to say some do. If your sweep turns up with some old curtains and a "Henry" or other domestic hoover this is probably a good indication as to the standard of work you can expect.
As a customer you want to know that the job you have paid for has been done properly by a competent person to recognised industry standards, after all your sweep is effectively undertaking safety maintenance in the heart of your home. 
My advice when choosing your sweep is to ensure they are registered with one of the industry approved bodies such as the National Association of Chimney Sweeps (NACS) or the Guild of Master Chimney Sweeps  (GMCS) this way you can be assured that your sweep is trained, qualified and carries the equipment necessary to do the job properly. Both NACS and GOMS work to the same standards and code of practice but don't forget to check on their websites to ensure your sweep is actually registered as a member.

Membership No 13/054



A Standard Open Fire set up



A sample of the equipment used



Why do I need to have my chimney swept?

Sweeping your chimney on a regular basis helps to remove the build up of soot, tar and other deposits that occur through the regular burning of carbon based fuels and therefore ensures there is a clear and safe passage for the exit of combustion by-products. All fuels contain carbon including oil, gas, wood, charcoal, coal and smokeless fuels and care should be taken to ensure flue ways remain clear and obstruction free. This will not only help prevent the risk of a chimney fire, but will also ensure your appliance burns efficiently and help prevent the production of carbon monoxide which results from the incomplete combustion of these fuels.
How often should I have my chimney swept?
This depends on the type of fuel used. Lincolnshire Fire and Rescue and the National Association of Chimney Sweeps (NACS) recommend:
  • Smokeless fuels - at least once per year
  • Bitumous coal - at least twice per year
  • Wood - four times a year (when in use)
  • Oil - once per year
  • Gas - once per year

What causes chimney fires?

Chimney fires usually occur because the deposits of combustion (soot, tar and creosote) are left within the flue ways. When high temperatures or flames from a very hot fire extend into the appliance outlet or flue they can ignite these deposits which in turn can lead to a serious house fire and cause structural damage to the chimney.

What is Carbon Monoxide?

Carbon Monoxide (CO) is a colourless, odourless, tasteless, poisonous gas that is produced from the incomplete combustion of carbon based fuels including gas, oil, wood and coal. It is only when the fuel does not burn properly that excess CO is produced. You can't see it, smell it or taste it and according to the Health and Safety executive around 20 people die each year as a result of CO poisoning from appliances and flues that have not been installed or maintained properly .

Should I fit a Carbon Monoxide (CO) Detector?

The short answer to this is a definite yes. All new installations are required to have a CO detector fitted in accordance with building regulations. CO detectors cost around £20, last for several years and could save your life. However a properly sited CO detector should be regarded as a last line of defense and is not a substitute for the proper fitting and maintenance of your appliance and flue. It has been a legal requirement since October 2015 for landlords to supply and fit Carbon Monoxide within their properties where solid fule appliances are in use.  

Do I need an external air supply for my appliance?

It is essential that your appliance and flue has an adequate supply of air to operate efficiently and to ensure that combustion gases are able to exit through the flue terminal.  All open fires and multi-fuel and wood burning stoves with a heat output above 5kw require an external air supply to operate efficiently, safely and to comply with current building regulations. Many problems occur as a result of the lack of an adequate air supply and often results in potentially harmful gases being allowed to enter back into the room.

Can I burn wood in a Smoke Control Area?

The answer to this question is yes and no. You are allowed to burn wood in a smoke control area or "smokeless zone" providing it is burnt on a DEFRA approved multi-fuel or wood burning stove that meets the requirements of the "Clean Air Act". Stoves that meet these requirements have a "secondary burn" system which forces combustion gases, that would otherwise exit into the atmosphere, back into the stoves combustion chamber resulting in more of the gases being burnt off.

Does it matter what type of chimney pot or cowl I fit?

The correct flue termination is essential to ensure your heating appliance (solid fuel, gas or oil) is able to work properly and safely. All appliances need to be able to breath in and out. There are many different pot and cowl designs available some of which are specific to certain types of appliances others are for capping off redundant flues. If you are unsure whether you have the correct pot or cowl you can check with your appliance manufacturer, HETAS registered installer or NACS sweep, all of which will be able to offer advice and guidance.

Does it matter what type of bird guard I fit?

There are both practical and safety issues to consider when fitting a bird guard to your flue terminal. Bird guards fitted to a flue serving Solid fuel appliances should have mesh no smaller than 25mm x 25mm to avoid the risk of deposits clogging up the mesh and potentially causing termination problems. In addition my advice would be to avoid the cheap wire "balls" that just sit in the top of your pot because when you come to have your chimney swept it is impossible to sweep all the way through your flue without knocking the guard off. The more robust guards which attach to the outside of your terminal usually allow the brush to exit the terminal without dislodging the guard providing adequate care is taken.

What causes a "smokey" fireplace?

A smokey fire place is probably the most common problem associated with burning solid fuels. Although there is no quick answer, as there are many factors that can prevent combustion gases from exiting your flue terminal, I have highlighted some of the more common problems below:
  • A dirty or blocked flue - this problem can be solved with regular sweeping of the flue.
  • Inadequate air supply - open a window about an inch and if this cures the problem then it is a good sign that your appliance and flue are not receiving enough air to allow the efficient extraction of the combustion gases. Fitting or clearing an existing external air supply will cure this problem.
  • Incorrect termination pot or cowl - different appliance types require specific pots and cowls to operate correctly. Check to ensure your pot or cowl is appropriate for the appliance it serves. If not change it.
  • Cold air trapped in the flue - For a chimney to work efficiently the air inside the flue needs to be at least the same temperature as the air inside the room. Cold air can sometimes become trapped inside the flue (external chimneys are particularly prone to this ) and in effect create a plug. To remove the cold air, warm the flue using either a blow torch or a torch made from paper prior to lighting the fire.
  • The "ratio" problem - this occurs when the flue is too small for the fireplace opening. A standard fireplace opening of up to 500mm x 550mm requires a minimum flue size of 200mm (8 inches ) to operate efficiently.
  • Pressure zones - A chimney requires negative air pressure to create its natural draw. A terminal exiting into a positive pressure zone (created by a prevailing wind) will prevent the gases exiting the flue terminal efficiently. This problem can be solved by extending the flue terminal above the pressure zone by either fitting a taller pot or extending the chimney structure. The fitting of an air supply on the same side as the prevailing wind may help to equalise the pressure at the top and bottom of the flue.
  • The down draught problem - Although there are circumstances which can conspire to create a genuine down draught, for example the prevailing wind being forced downwards onto the terminal as it flows over taller adjacent objects such as trees and buildings, these are rare. The down draught problem is more likely to be an up draught problem (or the lack of one) created by one or more of the problems above. However, a genuine down draught problem can be solved by the fitting of a suitable cowl or the construction of a "slab top" above the terminal.
I recently swept a flue serving an open fire for a customer who was convinced he had a down draught problem and as a result had a local builder fit an "anti down draught cowl" which the customer says made the problem worse. A few simple checks revealed that the real problem was the lack of an adequate air supply and the cowl fitted was actually a "flue vent stopper" designed to cap off redundant flues!

Why does my fire burn out of control?

There are several reasons why you may find it difficult to control the rate of burn within your multi-fuel or wood burning stove. It may simply be that you are burning the wrong type of fuel for your appliance. However it is probably more likely to be the lack of control over the amount of air allowed to enter the fire box. All stoves have air vents (some have flue dampners) which allow air to be regulated once the fire is established however, it is common for seals to perish or doors to warp which can allow air into the appliance even though the vents are closed. A simple test to check the integrity of your door seal is to attempt to trap a sheet of paper when the door is closed. If you can remove the paper without opening the door then the seal is potentially compromised.

Will you get soot all over my carpet?

No. All precautions are taken to ensure the surrounding area and appliance are protected and any soot and debris fall is contained within the appliance or fire place. The only sign that your sweep has been may be a slight sooty smell which will quickly clear and of course the certificate that will be left on completion.

A standard "open fire" set up

What type of wood is best to burn?

This is a question that I regularly get asked. Although some types of wood have a higher heat output than others, generally hard wood such as Oak, Ash, Yew and Beach will burn hotter and longer than softer woods. Avoid Firs, Spruce, Willow, Chesnut, Alder and Holly as these have poor heat output and can cause sap deposits to stick to the inside of the flue.
The important thing to remember is that your wood needs to be dry (seasoned) to burn efficiently, ideally with a moisture content of no more than 25%. Burning wet or "green" wood is the biggest single cause of tar build up within the chimney flue.

What is the best way to store wood?

Wood should be stored stacked, off the floor with roof and side protection. This will allow adequate ventilation and the movement of air to help the drying process and help prevent fungi growth. Lynx Outdoor Products based in Legbourne can supply a range of off the shelf and bespoke wood stores ideal for the task.
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