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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 gauge, 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 gauge which in consequence
gives no information about pollution by smoke. To obtain such information
a smoke filter is necessary.