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77
by the fitting of a circulatory system for gassing and ventilation.
By passing a current of air from the chamber through the Zyklon
tin and circulating this gas/air mixture through the contents of the
chamber it is possible to distribute the fumigant in a very short
period of time. Rapid and efficient distribution of the gas is of
great importance in fumigation technique, as the minimum quantity
of fumigant toxic to the insect pest can be used, thus avoiding
unnecessarily high concentrations forming in furniture and the
necessity for long periods of ventilation. With this increased
efficiency of gas distribution and subsequent ventilation it is possible
to reduce the exposure and ventilation periods considerably.
The apparatus consists of circulatory and exhaust pipes which
are connected respectively to a four-way cock, a Zyklon generator,
fan and motor. The operation of the chamber is simple:—
1. The loaded van is run into the chamber and the chamber
doors are clamped tightly.
2. The Zyklon generator is opened and a Zyklon tin containing
one kilogramme of available hydrogen cyanide is
placed inside it and the generator closed. This operation
may be likened to placing a cartridge in the breech of a gun.
3. The four-way cock is then given a half turn to such a
position as to allow circulation.
4. The fan, which is capable of giving a predetermined number
of air changes per hour, is then switched on.
5. The handle of the Zyklon generator is rotated for several
revolutions in both directions. This has the effect of
perforating the Zyklon tin at both ends and allows air to
be drawn from the chamber by the fan, passed through the
Zyklon tin and back into the chamber.
6. After 20 to 30 minutes the fan may be switched off and the
van left in the now equally distributed gas/air mixture
for a further hour or so.
7. To ventilate the chamber another turn is given to the
four-way cock so as to allow fresh air to be drawn right
through the contents of the van and discharged'from the
exhaust pipe into the air.
8. During this ventilation period chemical tests may be taken
of the atmosphere in the chamber,