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Chimney height approval

Why is chimney height approval required for certain chimneys?

The Clean Air Act, 1993, introduced a range of regulations to control smoke emissions and the height of new chimneys.

We must approve the chimney height and associated arrestment plant of large boilers and furnaces to ensure that emissions are at a safe height and dispersed sufficiently in to the atmosphere and not be detrimental to health or cause a nuisance.

The application for chimney height approval enables local authorities to take into account a number of relevant factors in determining the height of a chimney.  These include the need to avoid down draught or down wash created by the chimney itself, or by buildings or topological features; to avoid the likelihood of the ground level concentration of combustion products becoming prejudicial to health or a nuisance.

When is chimney height approval required?

We must approve the height of any chimney associated with a furnace (except a domestic furnace) or boiler if you burn

  • Pulverised fuel
  • At a rate of 45.4 kg or more an hour any other solid matter, or
  • At a rate equivalent to 366.4 kW or more any liquid or gaseous matter

If you are intending to carry out any of the following activities and any one of the above criteria apply, then you need to apply for chimney height approval from the council:

  • construct a new chimney
  • increase the combustion space of an existing furnace
  • add a new furnace to an existing installation
  • change the fuel burnt in an existing furnace
  • replace a furnace with one having a larger combustion space

How much does it cost?

Application for approval is free of charge

Application for chimney height approval

If you wish to build a chimney you must apply for consent first by completing a: Chimney Height Approval Application Form (PDF 136kb). If you would like a paper copy then please contact us.

Once you have completed the application form post or email the form back to us on the address given below.

An application for chimney height approval must contain adequate information to enable the necessary calculations to be carried out.


The Secretary of State has produced the following guidance on the calculation of chimney heights:

HMIP Technical Guidance Note D1: Guidelines on Discharge Stack Heights for Polluting Emissions. Published by HMSO, ISBN 0-11-752794-7

This guidance note is now unfortunately out of print, however you can request a copy from the British Library.

The third edition of the 1956 Clean Air Act Memorandum on chimney heights (issued with Joint Circular DoE 25/81 Welsh Office 12/81 also provides technical guidance

Application process

We will consider the application and give a written decision within 28 days of receipt, unless it is agreed in writing that a longer period may be allowed. If we fail to deal with the application within this time period, then approval without qualification is given.

We cannot approve the proposed chimney height unless we are satisfied that it will be sufficient to prevent, so far as is practicable, the smoke, grit, dust, gases or fumes emitted from the chimney from becoming prejudicial to health or a nuisance, having regard to:

  • the purpose of the chimney
  • the position and descriptions of buildings near to it
  • the levels of the neighbouring ground
  • any other matters requiring consideration in the circumstances

We can attach conditions to the approval, such as the rate and quality of emissions from your chimney.

Supplementary technical assistance for estimating the minimum permissible chimney height for small boilers emitting sulphur dioxide has also been prepared by Stranger Science and Environment at the request of the Department of Environment, Food and Rural Affairs and is available by calling 020 792 6119.

Exempt chimneys

A chimney may be exempt if it is used as part of:

  • a temporary replacement, for example if the boiler or furnace is being repaired
  • a temporary source of heat or power for building works
  • auxiliary plant to bring main plant up to operating temperatures
  • a mobile source of heat or power for agricultural purposes

Control of dust and grit from furnaces

The Clean Air Act 1993 also requires, subject to certain exemptions, that furnaces with a heating capacity greater than 16.12 kilowatts are to be provided with plant for arresting grit and dust as approved by the Local Authority. If your appliance has a capacity greater than 16.12 kilowatts you may be asked for further information to satisfy these criteria.