Clean Air Act The Clean Air Act, 1993, introduced a wide range of new regulations such as those which control smoke emissions, the height of chimneys and those relating to the content and composition of motor fuels. The control of chimney heights enables local authorities to take into account a number of relevant factors in determining the height of a chimney. Under section 14 of the Act, unless the height of the chimney has been approved by the local authority and any conditions attached to approval are followed, it is an offence to cause to cause or knowingly allow a furnace to be used to: Burn pulverised fuel. Burn at a rate of 45.4 kg or more an hour any other solid matter. Burn at a rate equivalent to 366.4 kW or more any liquid or gaseous matter. An application for chimney height approval must contain adequate information to allow for the necessary calculations to be carried out. The local authority must consider an application of approval for chimney height for a furnace and give a written decision within 28 days of receipt. There can be an agreement in writing between us and the applicant if a longer period is allowed. If we fail to deal with the application within this time period, then approval without qualification is given.