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persons are coming and going in the Bakehouse. Haldane has
pointed out, that, as a general rule, the air in basements is
relatively pure on this account. But, during the night, when
work is proceeding, such conditions do not pertain in the same
degree. The shop is shut, the staircase opening is closed, often
the ventilators are closed and the air is not changed. The
examinations were, therefore, made at a time favourable to the
Bakehouse than otherwise. The exact position of the Bakehouse
and the proximity or otherwise of areas also affects the question.
Out of the 46 underground Bakehouses 41 have no part above
the level of the ground. Many of them also have practically no
area, whilst others such as B. and H. have areas. This is
probably one reason why the C02 in B. and H. was lower
than in C. which, like many other Bakehouses, is a "well."
(b) The Temperature and Humidity.— The following
table contains the records of temperature and relative
humidity inside and outside eight typical underground Bakehouses
and one typical aboveground Bakehouse, in each
case the records being taken at the same time. It may he
explained that the relative humidity (or moistness) of the air is
the amount of moisture present in the air expressed as a per
centage of the amount of moisture just necessary to cause
saturation, 100 representing saturated air, or air carrying its
maximum degree of moisture. The relative humidity generally
accepted as standard in this country is about 70-75. A very fine
dry day would record, say, between 50-60, a damp day would
record about 90.