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DAILY MEAN CONCENTRATION OF SMOKE AND SULPHUR DIOXIDE
A daily record has been kept since the 1st November, 1958 of the
amount of smoke or suspended matter and sulphur dioxide in the air by
means of a smoke filter and volumetric sulphur dioxide apparatus
installed in Manor Park House.
It has long been recognised that a distinction must be drawn between
relatively coarse particles of solid matter which are quickly deposited by
their own weight, and which comprise most of the particulate matter
collected in the deposit guage, and the very fine particles which settle
slowly, if at all. These fine particles, commonly referred to as 'smoke',
are less than about 20 microns (0.002 cm) in size and consist largely of
carbonaceous matter, including tar, produced by the incomplete combustion
of coal; some fine ash is also included. It is important to realise that little
of this fine material is collected in the deposit guage which in consequence
gives no information about pollution by smoke. To obtain such information
a smoke filter is necessary.