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Chimney height approval

Height of chimneys (Clean Air Act 1993 ss 14-16)

At whatever height smoke and flue gases are discharged, gravity will eventually bring the larger particles of grit, dust and soot to the ground. Additionally, because of the natural turbulence of the atmosphere, a proportion of the gases and of the freely suspended fine particles will reach the ground although not affected by gravity. The higher the point of discharge and the greater the total heat content of the discharges gases, the more widespread and diluted will be the fine particles and gases by the time they reach ground level.

Controlling chimney height

The control of chimney heights 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 downdraught or downwash created by the chimney itself, or by buildings or topographical features; to avoid the ground level concentration of combustion products becoming prejudicial to health or a nuisance; in the case of smaller units to prevent the flue gases from entering nearby buildings in too high a concentration.

Under s.14 of the Act, unless the height of the chimney has been approved by the local authority and any conditions attached to approval adhered to, it is an offence to cause or knowingly permit a furnace to be used to:

  • burn pulverised fuel;
  • burn at a rate of 45.5 kg or more an hour any other solid matter, or 
  • burn at a rate equivalent to 366.4 kilowatts or more any liquid or gaseous matter 

Application for chimney height approval

If you are building a chimney, you need to apply for consent first. The application form must contain adequate information to enable the necessary calculations to be carried out.

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

Approval process

We'll consider the application and give a written decision within 28 days of its receipt, unless it's agreed in writing that a longer period may be allowed. If we fail to deal with the application within the agreed period, then approval without qualification will be deemed to have been 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