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Why should I have my chimney swept?

For 2 main reasons:

  • To reduce the possibility of a chimney fire.
  • To reduce the volume of obnoxious or toxic gases (especially carbon monoxide) entering a room.

A cleaner chimney is a safer chimney

Why is an un-swept chimney more likely to catch fire?

An un-swept chimney above a used open fire or solid fuel burner will have deposits of soot or creosote or both present on its inside surface. The deposit will depend on the fuel being burned and the temperature at which it was burned.

As wood burns it gives off volatile hydrocarbon fumes which gives it the distinctive smell. These rise up the flue and some of them will condense into tar droplets as they come into contact with the cooler higher surface of flue. As it cools this tar will form creosote which is highly flammable at the right temperature – a temperature that can be reached inside a flue.

Soot is incompletely burned carbon and gets released from the fire at a later stage of the burning process than the hydro carbons that produce creosote. Soot is also flammable and will burn at the right temperature. Once hot enough it can be ignited by a stray ember floating up the chimney in the draft. Alternatively it will spontaneously combust if sufficiently heated.

If these soot and creosote deposits are not periodically removed on a regularly used appliance they will build up over time slowing the exit of subsequent exhausting gases causing them to cool and deposit more soot and creosote making the problem worse. Over time this soot and creosote builds up and comes lower down the chimney closer to the heat of the appliance which further increases the risk of them catching fire.

Chimney fires are dangerous and can quickly spread beyond the chimney itself into other parts of the building. A chimney that has had a fire should be inspected and any damage must be repaired before it can be safely used again which can involve a need to re-line the chimney.

Why is an un-swept chimney more likely to cause toxic fumes to spill into the room?

If the deposits that condense on the inside of a flue are allowed to build up they will start to reduce the size of the flue and the efficiency with which it can exhaust the toxic fumes from the appliance below. If these toxic fumes do not go up the flue they’ll come into the room.

This can, but won’t necessarily, create an unpleasant smell in the room causing the user to take preventative action. Among these gases is carbon monoxide which is highly toxic to humans and animals but is invisible and has no smell so can go undetected. The toxic effects of carbon monoxide cause many symptoms which are likely to be mistaken as originating from other causes, explained below, and can lead to death.

Carbon monoxide poisoning is more common than most people realise and very poorly understood by the public at large. At the very least ensure a carbon monoxide alarm is fitted in any room you have with a solid fuel appliance and better still read up on carbon monoxide poisoning, how to prevent it and how to read the symptoms. See further down this list for more information.

Why is carbon monoxide (CO) dangerous and what are the symptoms of CO Poisoning?

Factors that contribute to the dangers of carbon monoxide (CO) are:

  • Lack of understanding of how easily it can be introduced into our breathing environment.
  • Lack of awareness of how toxic a gas it is and how its toxicity accumulates.
  • The fact that it is invisible & has no smell so can easily go undetected by humans and animals.
  • The fact that the symptoms of CO poisoning are similar to everyday symptoms of other causes such as flu or food poisoning so often get mistakenly attributed to other causes.

All domestic burning appliances will give off some CO and at low densities this is not an issue. Inefficient burning generates higher volumes of CO which again doesn’t have to be a problem to health if this goes up a flue and is expelled at the top rather than into the room. If this comes into the room however it can become a serious problem. CO is slightly lighter but similar in density to air and is generally warm as it is released so rises slowly and accumulates from the top down though this will depend on how much air circulation there is in the room.

CO is toxic to humans because it weakens the body’s mechanism for circulating oxygen. CO binds around 200 times more strongly to the haemoglobin in the blood than oxygen. Haemoglobin is the part of the blood that is used to transport oxygen from the lungs to the rest of the body. If we breathe in CO it clogs up the ‘oxygen receptors’ on the haemoglobin preventing the oxygen bonding and thus starving us of oxygen. CO effectively “chokes us without strangulation”. Once bonded the CO isn’t going be displaced from the haemoglobin other than by special treatment. The normal way the body gets rid of it is as the blood cells are replaced over time (years). The effect of CO poisoning is thus cumulative. We can’t receive relief by going outside and breathing fresh air (though we obviously escape further CO poisoning this way) – once clogged with CO our blood stays that way unless treated or replaced.

Early symptoms of CO poisoning can be very similar to many common ailments and are often mistaken for flu, viral infections, food poisoning or even just tiredness. These symptoms, which affect different people in different ways and different orders and not necessarily all together, are:

  • Tightness across the forehead
  • Tiredness, Drowsiness
  • Headaches – which can get severe
  • Dizziness, Confusion, Erratic behaviour
  • Nausea, Stomach pains, Vomiting
  • Breathlessness, Chest pains
  • Loss of vision
  • Collapse, Loss of consciousness
  • Death

If you suspect you are suffering from CO poisoning then take immediate measures to prevent the problem getting worse (turn off the appliance causing the problem, ventilate or leave the property immediately), go to your doctor or call NHS Direct on 0845 4647 or if the symptoms are severe call 999 and ask for an ambulance explaining you believe you have severe CO poisoning.

Do not resume burning your appliance until it has been checked by an approved chimney sweep or a HETAS registered installer.

What sort of drafting problems might a chimney have?

A chimney needs to be designed and sized to draw exhaust fumes appropriately from the appliance (open fire or solid fuel burner) it serves. There is a section in the Building Regulations dedicated to this topic and properly constructed chimneys will conform and thus usually work, or draw, well for their appliance. A properly drawing chimney will blow no smoke back into the room. The chimney draw also depends on other factors which can change and cause problems. For instance:

  • A chimney may fail to draw when it is windy outside due to down drafts.
  • A chimney may fail to draw properly because the appliance under it is not sealed to the chimney.
  • A chimney may fail to draw properly because its air vent has been blocked off or the ventilation is insufficient because the room insulation has been improved since the chimney was installed.
  • A chimney may smoke initially while it’s cold (at start up) but work fine once it is warm.
  • A chimney may fail to draw properly due to a pressure inversion outside.
  • A blocked chimney might always fail to draw properly. Blockage could be a bird’s nest or a brickwork/lining collapse.
  • A chimney that smokes when the appliance is not lit may be doing so due to leakage or siphoning from another chimney.

If you have any of the above or other chimney problems I’d be happy to help you sort them out which might involve nothing more than ‘phone call. Feel free to give me a call if you’d like to discuss a problem.

How often should I have my chimney swept?

This strays slightly towards the proverbial “How long is a piece of string?”. Appropriate sweeping frequency will depend on various factors but general guidance is as follows:

Fuel Sweeping frequency
Smokeless fuel At least once a year
Bituminous coal At least twice a year
Wood Quarterly while in use
Biomass At least once a year
Oil Once a year
Gas Once a year

I’d be happy to discuss this if you’d like some guidance.

What sort of safety checks will be performed while my chimney is swept?

As well as sweeping your chimney I’ll check the safety of the chimney and appliance in a number of ways. If your chimney is dangerous to the extent that it threatens life I’ll warn you of this and I won’t be able to sweep it at all. The safety aspects I am required to check are as follows:

  • ‘Building regulations conformity check’ drawing your attention to any irregularities.
  • Presence of a working carbon monoxide alarm.
  • Whether the room ventilation is appropriate for the chimney
  • Smoke evacuation test to verify the chimney draws properly

I’ll explain my findings and answer any questions you have on them and I’ll record them on the sweeping certificate which I’ll leave with you.

How do you get rid of a birds nest in a chimney?

Any birds nest present in a chimney over a working appliance (an open fire or a solid fuel burner) can lead to serious problems such as a chimney fire if the nest catches fire, or a blockage which can cause toxic fumes to enter the room below. Any such nest needs to be removed before safe use of the appliance can be resumed.

Birds nests will be contaminated with bird droppings, and when disturbed will create dust containing bacteria that it is sensible to avoid breathing in, for which reason they should be removed by someone with appropriate personal protective equipment. I have such equipment and I have fittings that can be placed on my chimney rods specifically for removal of a birds nest and will be happy to do this for you. Jackdaws are notorious for building nests in chimneys – depending on how long a nest has been there and how busy the birds have been you may be surprised at the volume of debris that comes out.

I’m thinking of having a wood burner (or a multi-fuel stove) installed – where should I start?

Installation of a wood burning or a multi-fuel stove is subject to building control in the UK. Unless you are already familiar with the building regulations (Approved Document J in particular) then get some advice before you start – and certainly before you spend money. Try reading the “Installation” page on this website or doing some other web research. Please give me a call and I’ll happily come and introduce you to what you need to consider and answer questions in more detail.

I’ve bought a wood burner (or a multi-fuel stove) can you install it for me?

That depends on a couple of factors. If stove has a CE data plate, is an appropriate size for where you want to locate it and all the constraints of the installation instructions can be met then I’m happy to consider it. If any of these conditions fail then I may still be able to help – please give me a call if you’d like to discuss it.

I don’t have a chimney but would like a wood burner (or a multi-fuel stove) – is this possible?

It may be. It is often possible to install a twin wall insulated chimney either through a building (see the diagram on the Installation page) or through a wall and up the outside of a building. The structure of the building is likely to constrain exact positioning of such a chimney and determine the scale of such a project. I’d be happy to help you consider whether or not a project of this nature in your home may feasible and give you some indication of the sort of cost involved so you can make a decision as to whether or not you think it would be worthwhile.

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