To protect against high concentrations of air
pollutants at ground level, which could create health effects, the
Clean Air Act 1993, introduced a wide range of new regulations such
as those which control smoke emissions and 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. The theory behind this is to
ensure that emissions from chimneys exit at high levels to aid
dispersion and dilution and limit the process of gravity from
bringing high concentrations of grit, dust, soot and gases down to
ground level.