b. The phosphine (not phosgene) gas has a pronounced carbide or garlic-like
odor which becomes increasingly objectionable with continued exposure. The odor
threshold varies with different people, but falls within a range of 0.005 to 0.5 ppm (parts
per million). The maximum allowable concentration (MAC value) for continuous 8-hour
daily exposure is 0.3 ppm.
c. Phosphine gas has excellent preparation characteristics; for example, it will
penetrate 30 to 50 feet into a stack of stored grain. The high velocity and vapor
pressure of the phosphine molecule permits deep penetration of even the most densely
packed commodities. The same molecular velocity that permits deep penetration also
produces highly desirable aeration characteristics. With normal ventilation procedures,
phosphine gas concentrations will be removed from both the product and the fumigated
stack of commodities within 60 minutes.
4-13. USES AND RESTRICTIONS OF ALUMINUM PHOSPHIDE
a. Aluminum phosphide is highly effective both as a stored-product and as a
structural fumigant, and is specifically applicable to the following:
(1) In-place fumigation of stored products indoors or outdoors under
polyethylene or vinyl coated tarpaulin.
In-transit fumigation of sealed box or hopper cars, standing or rolling.
Structural or space fumigation for both stored product and dry wood
Fumigation of raw agricultural commodities with or without tarpaulin.
b. Phosphine is highly toxic to all forms of human, insect, and other animal life.
For this reason, application should be closely supervised by the engineer or medical
entomologist. Personnel engaged in the application of this fumigant should be certified
and specially trained.
c. Phosphine gas is explosive under vacuum conditions. Therefore, its use is
restricted to atmospheric fumigation with or without a tarpaulin or cover. Cloth or
canvas tarpaulins are not suitable for fumigation purposes. Polyethylene or vinyl-
coated tarpaulins are satisfactory when properly sealed to the floor or base surface to
prevent gas leakage.
d. In accordance with USDA label instructions, aluminum phosphide must not be
used in such a manner to allow the pellets/ tablets or unreacted residues (ash) to come
in contact with any processed food.