Ansell Chimneys

01923 661 614

07941 282 325

07976 318 160

Ansell Chimneys

chimney sweep

stove installation

Full range of multi fuel and wood burning stoves

Chimney Sweeping Frequently Asked Questions

Which areas do you cover?

Ansell Chimneys are based in Watford and we cover all areas of Hertfordshire and Bedfordshire.

Fire not burning properly?

A fire that does not burn properly or more or less constantly trickles smoke back into the room is generally the result of inadequate maintenance or a flaw in the design.

Has the chimney been swept recently? If not, why not try this first. it's cheaper than many of the alternative solutions!

If you are satisfied that the flue is clear and not obstructed by either deteriorating internal masonry or by soot, then you need to start looking at the design of the fireplace/chimney itself.

Insufficient air (air starvation)

An open fire requires a free supply of air for two purposes.

  • Primary air which allows for combustion
  • Secondary air, which carries the smoke away up the chimney

Primary air demand is usually small and is often supplied below the bed of the fire.

Secondary air demand is much greater and it is this that prevents the smoke spilling out of the fireplace. If your floors are solid concrete, and the windows and doors are new (and are fitted with draught strips), then there may be no route for an adequate volume of air to come into the room.

Fireplace too large

If the fireplace opening (height x width) is more than seven times the cross section of the flue, smoke spillage can occur.

Inadequate internal design

To work properly a fireplace needs a proper "throat" and be "gathered" into the flue (if you need to know more about the meaning of these and other terms check the glossary on this site).

Large voids inside the chimney where turbulence can occur, sudden changes in internal section rather than gradual transitions, inadequate throating and smoke shelf, poor fireplace and smoke chamber geometry, can all lead to smoke spillage even though the fire opening is correct. This will probably be in the form of continuous wisps of smoke escaping from the fireplace.

Does your chimney smoke?

  • Frequently or perhaps even all the time
  • Just occasionally

A chimney that smokes frequently or all the time is unlikely to be caused by downdraughts. A genuine downdraught is caused by pressure at the top of the chimney being greater than that in the room where the fire is; it usually occurs only in high winds.


An occasional burst of smoke apparently blown back down the chimney, particularly in high winds, may be the result of downdraught. A downdraught is caused by pressure at the top of the chimney being greater than that in the room where the fire is.

It generally means that the top of your chimney is being "overshadowed" by some other structure nearby such as the top of the roof; or something is causing the pressure at the bottom of the chimney to fall usually an exposed chimney on the outside of an old house, into which the cold wind has found a way where, for example, the brickwork has become porous.

First, check the top of the chimney. Is it well above any nearby structure such as the ridge of the roof (where "well above" means 0.6m if the chimney is less than 0.6m from the ridge and 1m or more if it is further away). Are there other tall structures, buildings or trees close by that might be interfering with the airflow? Can you do anything about any such interference? If not, a solution might be to increase the height of the chimney. If you are satisfied that the top of the chimney is not being "overshadowed", look instead at its situation. How exposed is it (is it, for example, facing the prevailing wind)? What is the state of the brickwork and mortar? Might cold draughts be getting through into the flue somewhere? Are there grilles and vents into the chimney that might be affecting the updraught?

In a new chimney, simply heating up the flue may solve the problem. In an old chimney, you may require a liner.

Why not call Ansell Chimneys now for a free quote

If you would like to know more or are interested in a quote we would be happy to help. Phone us on 01923 661 614, email us at or fill in our enquiry form and we will be in touch as soon as possible.