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cyanide, lead, muriatic acid, nitric acid, paraffin oil, selenium, sulphide, zinc, and
metal recovery. Electricity generating stations and gas works also are dealt with by
the Alkali Inspector.
Recent years have brought a big change in regard to the emission of smoke
from factory chimneys. Smoke results from inefficient combustion, and the current
cost of fuel makes waste a costly matter. Labour costs are also a major factor for
industrialists, and it is generally uneconomic to employ stokers to feed furnaces by
hand. As a result most modern furnaces are fitted with controls which automatically
adjust fuel and air supply, and ensure optimum combustion conditions.
Observations are made on factory chimneys, and any emission of smoke which
exceeds the permissible limits is investigated. It is usually found that such smoke
arises from mechanical failure in the plant, and that conditions can be quickly
remedied. In difficult cases, technical advice can be obtained from the National Coal
Board, the major oil companies or the National Industrial Fuel Efficiency Service.
The power in the 1956 Act to deal with dark smoke has been extended by a
provision in the 1968 Act. With certain exemptions it is now an offence to emit dark
smoke from any industrial or trade premises. The former power referred only to
dark smoke from chimneys.
With modern plant the main pollution problem is the emission of sulphur
dioxide, the amount depending not only on the size of the furnace but on the
sulphur content of the fuel. In heating of factories and warehouses there is a trend
towards warm-air heaters which burn a light distillate oil with low sulphur content.
There is also an increase in the proportion of boiler plant using this fuel. The higher
cost of distillate oil is in some measure off-set by easier maintenance, cleaner handling
and simpler equipment. A change to low sulphur content fuel would be a major
contribution towards reduction in air pollution. It is interesting to note that in New
York there is a local statute which limits the sulphur content of fuel used in the
City, and that within a few years a sulphur content of not more than 1% will be
required for both coal and residual fuel oil.
An important factor in air pollution is the ground level concentration of sulphur
dioxide. This is dependent on chimney height and the degree of dispersion of flue
gases before they reach the ground. Changes in legislation incorporated in the 1968
Act apply control of chimney height to furnaces burning 100 lb. or more of solid
fuel per hour, or burning liquid or gaseous matter at a rate equivalent to 1^ million
or more British Thermal Units per hour. Formerly control was exercised when plans
were submitted for Building Regulation approval. Under Section 6 of the 1968 Act.
the control is now more direct, and it is an offence to use a furnace above those
capacities unless the height of the chimney has been approved by the local authority.
The provision applies to new furnaces, new chimneys to existing furnaces, furnaces
with increased combustion space, and furnaces replacing smaller installations.
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