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EXPERIMENT ON THE IRRADIATION OF THE UPPER AIR
IN SCHOOLS
The report has now been published of the results of the investigation, made in six
schools in the Borough of Southall, on the effect of Ultra Violet Irradiation of the upper air
on the disinfection of the school atmosphere and its effect on the occurrence of illness
amongst schoolchildren. The investigation was carried out by the Air Hygiene Committee
of the Medical Research Council and three of the schools were used as experimental premises
having the Ultra Violet lamps installed while the other three were used as controls, with
dummy lamps, in order that a full comparison could be made. By agreement with the
Medical Research Council and the permission of the Controller of H.M. Stationery Office
having been obtained, a summary of the conclusions obtained from the experiment is quoted
below. It win be seen that although it was thought that the results obtained in the reduction
of the incidence and transfer of infectious disease did not justify the use of ultra violet
lighting of the upper air as a general practice, that much information with regard to the
ventilation, heating and other requirements in schools was secured and indeed a great deal
of information was obtained during this piece of research which is still being examined
and which will no doubt be of great value not only in future experiments, but also in the
design of new schools.
An Extract from Report 283 of the Medical Research Council on Air Disinfection
with Ultra-Violet Irradiation
Summary
All the classrooms and assembly halls of the Infant and Junior departments of each of
three primary schools in the borough of Southall, a suburban area of Greater London, were
equipped with ultra-violet lamps to irradiate the air in the upper part of the room. Three
similar schools were observed as non-irradiated controls. The child population of the
irradiated schools was about 1,550, and that of the control schools about 1,860. Observations
were continued for a period of three years from January, 1946 to December, 1948,
the irradiation being maintained during school hours throughout the whole period.
Records were kept of all the absences and the reasons for absence of any child who
was away from school for one whole day or more. In general, reliance was placed upon
parents' diagnoses but in any case of doubt the home was visited for further inquiry.
Throughout the three years daily visits were made to a random sample of classrooms,
while they were occupied in the ordinary way, for the determination of the temperature,
humidity, ventilation rate and bacterial content of the air. Measurements were also made
at intervals of the ultra-violet intensity in the rooms.
The average ultra-violet intensity in the upper region of the irradiated rooms was 8 to
13 microwatts per sq. cm. At desk level the intensity varied between 0.1 and 2 microwatts
per sq. cm. according to the nature of the ceiling. The irradiation produced no ill-effects
among either children or teachers.
Although differing somewhat in structure, the irradiated schools did not on the average
differ from the control schools in temperature or humidity, and were not materially different
in size of class or area per child; their average ventilation rate (676 air changes per hour)
was slightly greater than in the control schools (6.17).
During the investigation the general bacterial count in the air was about 16 per cent.
lower in the irradiated schools than in the control schools. The count of Str. salivarius,
studied as an index of the degree of mouth pollution of the air was reduced by as much as
70 per cent.—from 0.191 colonies per cu. ft. in the control schools to 0.053 colonies per cu. ft.
in the irradiated schools. The count of haemolytic streptococci, made over a period of
about six months was reduced by about 80 per cent.
There was no appreciable effect on the total sickness absence recorded in either the
Infant or the Junior departments. Examination of individual causes of absence suggested,
however, that the irradiation probably reduced the number of absences due to certain
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