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SMOKE
What is smoke? The dictionary says that it is "any volatile
and especially any carbonaceous matter escaping from a burning
substance”: in simple language, what this means is that the
substance is not being burned properly—it is smouldering rather
than burning. When combustion takes place, the material,
whether it is coal, wood or paper, if its temperature is raised
sufficiently, combines with the oxygen in the atmosphere, and
heat is given off. The carbon in the fuel unites with oxygen to
form carbonic acid gas —a harmless product; the hydrogen
becomes water vapour. If there is not enough air-supply a good
deal of the carbon and other constituents are only partly burned
or not burned at all: the amount of dark smoke which is
produced is a measure of the degree of combustion.
Coal is a very complex substance. It has been evolved
from the carboniferous forests of millions of years ago, which
decayed, were buried and compressed, and which have given us
a priceless storehouse of energy and a rich source of chemicals
for use in industry and medicine. It is sad to think that we
allow so much of this treasure to be dissipated up the chimney.
The value of coal as a source of heat is due to the large amount of
hydrogen and carbon it contains. Peat, which is the half-way
stage between the forest and the coal-seam, contains about
50 per cent. of carbon; bituminous coal which is a later phase
in evolution contains a little more; while anthracite, the final
step, has more than 90 per cent. Coal is made up of many more
substances, which are given off as sulphur gases, oils and tars,
when combustion takes place. It is clear that the greater the
proportion of carbon (as in anthracite and coke) and the less the
amount of organic substances, the better will be the chance of
preventing unnecessary smoke and decreasing the amount of
pollution of the atmosphere.
How can we prevent smoke?
It will be seen then that there are two fundamental principles
in the prevention of undue smoke when combustion takes
place: a suitable fuel, and a correctly designed appliance in
which enough oxygen is available to ensure complete burning.
It is evident, therefore, that the open (bituminous) coal fire has
all the disadvantages. It is wasteful, expensive, dirty and causes
unnecessary work for the housewife. It must produce a great
deal of smoke and grit. It is a natural law that when air gets
warm it rises, and the air above the coal fire is no exception.
Up the chimney it goes, carrying with it fine particles of dust