6.1 Introduction
Various chemicals that can exist in the gaseous state in
sufficient concentration to kill pests are used as fumigants; however, although
active in gaseous form they may actually be applied as a liquid or even a solid.
Some gases are supplied liquefied under pressure in steel cylinders or other
pressure containers: others, which are liquids under normal atmospheric
conditions, can be stored and transported in drums or bottles. Certain solid
substances are used which, though not themselves fumigants, undergo chemical
reactions with atmospheric moisture at the site of use and release a fumigant
gas, e.g. aluminium phosphide which releases phosphine, and calcium cyanide
which releases hydrogen cyanide. Although specific precautions may be necessary
for a particular fumigant, there are certain systematic and well-proven
procedures which should always be followed to ensure safety of fumigators and
other persons and to optimalise fumigant
effectiveness.