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Volumetric Method
The daily mean concentration of smoke and sulphur dioxide is measured by volumetric
apparatus in the Manor House.
The gauge faces west and a main road in a built up area of residential and commercial
premises.
The term "smoke" is used to denote all fine suspended impurity collected by the test
filter and expressed as milligrams per 100 cubic metres.
The term "sulphur dioxide" includes all acid producing gases in the air with the exception
of carbon dioxide and is the net acidity of the air calculated until March 1961 as
sulphur dioxide and expressed as parts per 100 million parts of air, but from April 1961 the
method of calculation was altered by the officers of the Fuel Research Station and from
that time the calculation was in microgrammes per cubic metre of air, so comparison with