What causes stoves and fireplaces to smoke?

What causes stoves and fireplaces to smoke?

Homeowners often ask what causes a fireplace or stove to smoke during use. If you are experiencing smoke problems from your solid fuel stove, here is a checklist for what to look out for. Please note this checklist is not exhaustive but should help you troubleshoot the most common causes of your stove smoking in your home. It may be that the cause is not one single issue but rather a combination of a number of different things.

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To ensure the chimney is capable of providing adequate draft for correct operation of your stove, the chimney system to which the stove is connected should confirm to the following requirements:

  • The flue/chimney should be continuous to the termination point with all joints sealed to prevent any possible air leaks.
  • Flue Height should be a minimum of 15 feet (4.6 metres)
  • Flue bends should be kept to a minimum and if possible, flue bends not exceeding 45° should be used.
  • Horizontal runs of flue pipe should be avoided where possible. Where a horizontal run of fl ue pipe is used it is advised not to exceed 6" (150mm).
  • Your flue liner needs to be sized correctly for your stove. Please consult specific installation instructions for your stove model for recommended flue sizes.
  • The chimney termination position should be above the main ridge of the roof or adjacent outside obstructions (i.e. high tress or other buildings).
  • The chimney serving the stove should not be shared with any other appliance.
  • Access should be provided to the chimney to allow access for regular cleaning.

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Owing to current building regulations and building standards, modern houses are more air tight than older houses primarily due to modern draught proofi ng and the fitting of double glazed windows. As a stove is an air using appliance, it will require a permanent air supply to the room in which it is installed as to allow the replenishment of air being used and being vented through the chimney system. This can be achieved by fitting a suitably sized air vent (consult with manufacturer's installation instructions) from the room to outside of the building. If the stove is installed in a room that also has an air using appliance (e.g. extractor hood, tumble drier etc), the permanent air vent should be sized to allow for the air requirements of the second appliance also.

A simple test for checking if a chimney's draught is being affected by lack of ventilation is to open a window and if the smoking stops it's a good indication that there is insufficient air to support combustion and to supply a steady draft through the flue/chimney. Please note this is only a short term solution and the route cause should be addressed.

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All of our stoves are tested & rated using good quality coal as the standard fuel. Burning the same quantity of turf/timber instead of coal will result in a lower heat output being achieved. The following can affect stove performance and result in possible smoking issues:

  • Continual low burning - Lower fuel temperatures produced by low burning will affect chimney performance.
  • Flue pathways should be cleaned periodically.
  • Usage of damp or poor quality fuel should be avoided.
  • Timber or turf should be seasoned for a minimum of 2 years.

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Smoking issues can also be directly attributed to experiencing down draught problems with the chimney system. Downdraught issues are usually caused by the following:

  • Flue termination point below the main apex of the roof.
  • Turbulence caused by adjacent flue termination points.
  • High trees or buildings in the vicinity of the flue termination point - if high trees are up wind of your chimney, higher pressure can be caused at the top of the chimney by the downward curl of the wind going over the tree or building beside you.
  • If you are experiencing downdraft problems even before stove installation or subsequently, a suitable anti-downdraft cowl should be installed. In the event of the cowl not proving sufficient, it may be necessary to extend the chimney so that all obstructions are cleared.

NOTE: If experiencing smoking or downdraft problems with your open fire, installing a stove will not rectify the situation

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