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64
The air escapes from the rooms by a separate system of exit ducts. The system
makes it necessary that all windows should be kept tightly sealed, and doors throughout
the buildings must remain closed, particularly the main outer doors of the
departments.
A certain number of complaints has been received from teachers working in the
schools concerned, but in almost every instance the complaints have been directly
caused by defects which it has been possible to rectify. On the whole the complaints
have been relatively few in number and less serious than the complaints arising in
schools naturally ventilated erected during the same epoch. From some of the
“plenum” schools there has never arisen a complaint in all the years during which
they have been established.
Much investigation and research has been carried out by the Council's officers
on the conditions in the mechanically ventilated schools. The first scientific observations
on the physical conditions of the atmosphere in these schools were made in
1903. The introduction by Dr. Haldane of a ready means of estimating the amount
of carbon dioxide in .the air made it possible to take a large number of accurate
observations in a short space of time.
The mechanically ventilated schools were visited and compared with neighbouring
schools which are naturally ventilated. It was found that, judged by the
amounts of respiratory impurity in the air during occupation, the “plenum” schools
were very distinctly superior to the ordinary schools. It is true that the “plenum”
schools differed amongst themselves in efficiency. While for instance at the “John
Ruskin” and at Cassland-road, the air was found on all occasions in a satisfactory
condition, at Christian-street and at Old Montague-street, the respiratory impurity
at times mounted above the margin which is considered permissible. This is owing
to the fact that in the latter schools the exit ducts are especially narrow, so that
while all the doors in every department are shut,satisfactory ventilation is maintained,
but when the doors are opened in one department for children to go out to play, or
for any other purpose, the system is short circuited and the full measure of air does
not reach the other departments. Even when thus temporarily upset, owing to
opening of doors, however, the air in these schools, judged by the carbon dioxide
present, was no worse than in the ordinary schools.
In 1911 the medical officer (Education) in conjunction with the Council's
chemist, made a comprehensive series of observations at Commercial-street School,
one of the schools ventilated on the “plenum” system, where complaints had at
that time found expression. A neighbouring elementary school, Chicksand-street,
was used as a control. It was found that, judged by the amount of carbonic acid
present in occupied classrooms, the air was superior in the “plenum” school at all
points to that in the school naturally ventilated. It was considered, however, that
the air, although sufficient in amount, was delivered too hot and dry to the classrooms,
and suggestions were made for improvements to the installation with a view to overcoming
this fault.
For four years between 1914 and 1918 a comprehensive research was carried
out upon “plenum” ventilated schools by one of the officers of the public health
department. The schools investigated were Berner-street, Christian-street, Commercial-street,
and South Hackney Central. The factors investigated comprised:
(1) heat, (2) humidity, (3) odour, and (4) air currents. Many thousands of observations
were made, and the results were uniformly in favour of the mechanically
ventilated schools as far as the physical factors enumerated above are concerned.
On many other occasions observations have been made during the past 22 years,
although not upon so elaborate a scale as those described. The figures and diagrams
relating to these observations are not reproduced in this report, but always the
tests have shown that the “plenum” schools have the advantage over ordinary
schools in regard to the sufficiency and purity of the air supplied, so far as these
can be gauged by mere physical measurements and considerations.