When smoke and flue gases are discharged from a chimney, at any height, sooner or later gravity will cause particles of grit, dust and soot to fall to ground level. In addition, turbulence in the air will result in a proportion of gases and fine particles also coming to ground. It is important that the height of any chimney is sufficient to avoid the likelihood of the ground level concentration of combustion products becoming prejudicial to health or a nuisance. Under Section 14 of the Clean Air Act, unless the height of a chimney has been approved by the local authority and any conditions attached to approval have been complied with, it is an offence to cause or knowingly permit a furnace to be used to:
- Burn pulverised fuel
- Burn at a rate of 45.4 kg or more per hour any other solid matter; or
- Burn at a rate equivalent to 366.4 kilowatts or more of any liquid or gaseous matter
These are commercial burning conditions and it is not expected that domestic furnaces would require this type of approval. An application form - doc for chimney height approval must contain adequate information to enable the necessary calculations to be carried out. We must consider an application for chimney height approval for a furnace and provide a written decision within 28 days of receipt, unless it is agreed in writing between us and the applicant that a longer period is allowed. If we fail to deal with the application within this time period, then approval without qualification can be given.