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Chemical tests were made at intervals, and it was found that the air in the house was clear of the gas
in about hours. The hot air was then applied to the bedding and upholstered articles, and after
a short time tests proved that these could be used without danger. The kill of bugs was enormous
and constant inspections throughout the summer proved that all eggs had been rendered sterile.
This experiment showed that a house fumigated in this manner could be slept in the same night.
The test was carried out in a detached house, and it led one to the view that it is not yet safe
to apply the method to the terrace type of house generally found in Kensington ; cracks in party
walls and chimney connections may result in a dangerous leakage from one house to its neighbour.
Close co-operation with the Natural History Museum has resulted in many experimental fumigations
with various chemicals, and although the perfect insecticide, suitable for use in dilapidated
houses, has not yet been discovered, an exceptionally high degree of success has been obtained.
Experimental work was commenced with crude orthodichlorbenzene. This chemical is sufficiently
toxic to kill bugs, but it is not volatile enough to reach minute cracks and crevices, where the eggs
are deposited. The advice of the government chemist was sought, and he suggested several
substances which might be used in conjunction with orthodichlorbenzene. Some flats at Sutton
Dwellings were treated with mixtures of orthodichlorbenzene and (a) methylene chloride and
(b) carbon tetrachloride. These mixtures were highly successful. Unfortunately, their cost is rather
high, and the presence of methylene chloride produced acute physical discomfort in all persons
present when this mixture was used. It has been impossible so far to obtain a suitable filter for a
gas mask in order to neutralise methylene chloride, and its use as a fumigant has therefore been
discontinued.
Two substances, when mixed with orthodichlorbenzene, have proved to be extremely satisfactory.
Orthodichlorbenzene and methylated spirit mixed in equal volume give a fumigant which
is toxic and highly volatile. When applied with a pressure spray, a particularly strong concentration
of gas is given off in a short time. This mixture is not suitable for furnished rooms, however, for
it has the effect of spoiling polished surfaces. A mixture of orthodichlorbenzene and white paraffin
oil gives equally good results and has the advantage of being non-staining. It is 98 per cent,
efficient, and is now used in Kensington as a routine spray in verminous rooms. Other experiments
have been undertaken, and some are still in hand ; and it is hoped to evolve a formula which will
be cheap and completely effective.
Interest m the disinfestation depot and in the experiments in fumigating dwellings has been
considerable from the beginning. Representatives from government departments, medical officers
of health from as far afield as Sweden, and sanitary inspectors and other officers in large numbers from
all over the country have visited Kensington and have gone away impressed by the work that is
being carried on.
Statement of work done in connection with disinfestation.
Period 1st July to 31st December, 1934.
Number of families' furniture removed and treated with hydrocyanic acid gas 399
Weight of furniture estimated at 600 tons.
Weight of bedding disinfected by steam 43 tons, 14 cwt., 1 qr., 21 lb.
Number of articles stoved :—
Mattresses and flock beds 1,820
Bolsters and pillows 2,925
Blankets and sheets 2,270
Sundries 2,237
Total 9,252 articles.
Number of houses treated with orthodichlorbenzene and other chemicals 157
,, ,, ,, hydrocyanic acid gas 41
In addition to the above, 437 houses were treated with sulphur during the course of
the vear.
Disinfection after Infectious Diseases, etc.

This table does not include the work carried out at Wood Lane on behalf of the
Paddington borough council.