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65
It may be asked, if the air in the “plenum” schools is sufficient in quantity and
pure in quality, why do teachers sometimes complain?
There are two factors to be considered, one physiological and the other mental.
The physiological effect upon the occupants of a building which is warmed solely
by heating the entering air is a somewhat enervating one. In ordinary life the
musculature of the body is kept in a condition of “tone” by innumerable stimuli
to the skin, arising from frequent small alterations of temperature of the air and by
the little eddies and currents of air to which our bodies are exposed under natural
conditions. When these stimuli are absent, as they largely are in the “plenum”
schools, there is some loss in muscular tone, and consequently a diminution in
alertness; the atmosphere is a drowsy one. This is the main objection to the
“plenum” system of ventilation and heating. The ideal conditions for health are
those that ensure sufficient warmth received by radiation through an atmosphere
relatively cool. The reverse of these conditions holds when the sole source of heating
a room is the entering air.
It is probable that the objections made by certain of the teachers working
under the system are due to mental effects produced by the physiological reaction
described. To this must be added the “caged-in” feeling which many experience in
a room in which it is impossible to open the windows, a feeling which amounts to a
mild form of what is termed in medical textbooks, “claustrophobia.” Enthusiasts
for the open-air life can never be happy under these conditions. The following
letter was written in 1912 to my predecessor by Dr. Garnett, who was then Education
Adviser to the Council.
“I enclose a little memorandum which I prepared for the Education
Officer on the ventilation of Commercial-street School. I do not want to trouble
you with any of the mechanical details, but I should be glad if you would
consider the following problem on the physiological and psychological basis.
”Under medical advice the Council is providing not only open-air schools
but open-air classes in the London playgrounds, and while in some schools
these classes are provided alike for strong and weak children, in other schools
it is the anaemic children who are specially selected to attend such classes. We
appear, therefore, to assume that, provided a child is warmly clad, the variable
conditions to which he is exposed in the open air are conducive to health.
“At the other extreme of our system we have the mechanically ventilated
school, in which no window may be opened because it disturbs not only the
ventilation of the particular room, but of all other rooms in the circuit, and
doors can only properly be opened provided that there is a second door closed
before reaching the open air. In a mechanically perfect system of forced
ventilation the air may be uniformly distributed among the occupants of the
room without any sensible draught, and the full amount which the most
extreme hygienist can demand may be supplied at a perfectly uniform temperature,
and always with the same pre-determined degree of humidity. As far
as known chemical, physical and mechanical conditions are concerned, the
system may be assumed to be perfect, and the occupants of the rooms are
exposed throughout the whole day to precisely the same conditions in all these
respects, and there is no demand made upon any of the regulating machinery
of the body to alter the adjustments pertaining to surface evaporation,
subcutaneous circulation and the like, while such machinery would be
constantly called upon for re-adjustments when the body is exposed to the
ordinary conditions of open air life.
“Between the purely natural conditions of life out of doors and the
apparently perfect conditions of living in a tube with an ample supply of pure
air, we have the ordinary conditions of natural ventilation in which there are
considerable differences of temperature and hygrometric conditions within the