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16
In the early trials in this Borough, D.D.T. Concentrate was diluted with ordinary
Pool burning oil to make a 5 per cent. solution. Subsequently, it was decided
to use a proprietary solution guaranteed to contain 5 per cent. D.D.T., and without
any unpleasant or objectionable effects.
Protection of Personnel. Although D.D.T. has been used extensively in
the Services without injury to personnel, repeated or prolonged contact with oily
solutions of the substance may cause absorption and dermatitis. Masks are therefore
worn when operatives are spraying, to prevent inhalation of the spray into the
respiratory system. Eyeshields are also worn when working in confined spaces ;
and the ordinary overalls have been found to be a sufficient protection for the body,
without causing the men to become unduly hot. The hands are protected with a
proprietary " barrier cream," a small amount of which is rubbed over the hands
and arms until dry, before commencing operations. It is claimed that this affords
complete protection against various oils, until washed off with water. No case of
skin irritation has occurred among the operators.
Method of Spraying. Although the proprietary preparations used contain
a "knock-down" ingredient in addition to the D.D.T., the main purpose in spraying
is not so much to kill bugs seen, but to provide a residual lethal film over the surfaces
of the room, so that any insects which subsequently travel over those surfaces
will be killed as a result of the contact with the D.D.T. film. It is therefore unnecessary
to remove any of the woodwork (architraves, skirtings, picture rails and
the like) as heretofore ; the bugs which may be hiding behind these fittings will
eventually have to come out in search of food, and they are therefore bound to
come in contact with the lethal surface. Nor is it now considered necessary to use
the blowlamp on bedsteads and other articles which are infested ; these, too, are
covered with a D.D.T. film after spraying, and become lethal to the insects. Even
the bedding (mattresses, pillows, etc.) is sprayed, so that there is no possibility of
a bug surviving even if it succeeds in reaching the bedding. The former practice
of treating bedding in the steam disinfector has been discontinued, except in unusual
circumstances. Where steam disinfestation is resorted to, the bedding is afterwards
sprayed with D.D.T. solution in order to prevent, as far as possible, further
infestation.
Apparatus. A spray of approximately half-gallon of solution to 1,000 square
feet of wall surfaces, plus one foot of the floor and ceiling nearest to the walls,
together with bedsteads, springs, frames, and both sides of mattresses, has to be
applied. Even in a comparatively small room, this involves the use of a considerable
quantity of solution. The ordinary hand-sprayer only holds about a
pint of solution, and the frequent refilling and consequent wastage, together with
the fatigue of manipulation of the hand-sprayer, render this form of apparatus
unsuitable for the new technique. The foot-operated pump sprayer, although
capable of dealing with fairly large quantities of solution, is inclined to be messy
inside houses, and there is also some fatigue in operation.
In order to overcome the objections to the former types of apparatus, and to
enable the operators to concentrate on their work without undue fatigue, frequent
interruptions for refilling, and wastage, it was decided to obtain a power-driven