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and the length of treatment, onsite monitoring of yam and chestnut
fumigations may be interrupted after the 2 hour reading when efficacy
and safety considerations warrant.
These instructions do not prevent the officer from leaving the
immediate fumigation site for brief periods when it is necessary and
safe to do so. The pest control operator must be notified of the PPQ
officer’s intended absence. These absences would ordinarily be limited
to 20 minutes and do not constitute a break in service. These practices
are in place in many locations and will require only minor
modifications in other areas.
Fumigation Guidelines
The following fumigation guidelines are in common usage throughout
this manual:
◆ Dosage rate is based on 1,000 cubic feet of enclosure space,
whether chamber, tarpaulin, van, freight car, ship hold, etc.
Dosage should be calculated from the volume of the tarped
fumigation enclosure.
◆ Dosages are listed by weight in the Treatment Schedules. If
liquid measures are needed, convert from weight to volume by
using the conversion figures.
◆ Ounces per 1,000 cubic feet (oz/1000 ft3) is equal to milligrams
per liter (mg/liter) and is equal to grams per cubic meter (g/m3).
◆ Volume of commodity being treated should not exceed two-thirds
of enclosure volume unless otherwise specified in a schedule.
◆ Specified vacuum should be held throughout the exposure
period.
◆ Blowers or fans should be operated as follows:
❖ for propagative material (T200-series schedules), the entire
period of exposure, whether NAP or vacuum
❖ under tarpaulin (and vacuum fumigation for other than
propagative material), fans should operate for 30 minutes
after gas introduction, or until T/C readings indicate uniform
gas distribution
❖ for all bulk material, forced recirculation is required, check
for uniform gas distribution by taking T/C readings at four or
five locations including at least three from the commodity
Important
Phosphine fumigations do not require fans.
Chemical Treatments Fumigants
Physical Properties of Fumigants
2-2-4 Treatment Manual 10/2002-04
PPQ
◆ In this section, all NAP treatments that refer to chamber
fumigations should be conducted in USDA-approved chambers.
(See Section 6, Certification of Vacuum Fumigation
Chambers).
◆ Methyl bromide treatment schedules are indicated as “MB.” MB
generally refers to any methyl bromide label. Specific MB label
restrictions are noted in this manual for the “Q” label. Always
check the label of the fumigant to be sure the commodity is listed
on the label. Commodities that are not listed on the fumigant’s
label are not authorized for fumigation with the manufacturer’s
gas.
Physical Properties of Fumigants
Fumigant
Chemical
Formula Boiling Point
Specific
Gravity1
1 Air = 1, anything greater is heavier than air.
Flammability
Limits in Air
Methyl Bromide CH3Br 3.6 °C 40.1 °F 3.27 Normally
nonflammable. Flame
propagation at 13.5 to
14.5% by volume only in
the presence of an
intense source of
ignition.
Phosphine PH3 –87.4 °C –126
°F
1.214 1.79% by volume
Sulfuryl fluoride SO2F2 –55.2 °C –67 °F 2.88 Nonflammable
Fumigant Odor Effects on Metals General
Methyl
Bromide
No odor at low
concentration. Strong
musty or sweet at
high concentrations.
Reacts with aluminum, may
damage electronic
equipment
Discharged from
cylinders, 1.5 lb
cans
Phosphine Garlic-like or carbide
due to impurities
Copper, brass, gold and
silver severely damaged;
electronic equipment
damaged. Other metals
slightly affected in high
humidity.
Evolved from
aluminum
phosphide or
magnesium
phosphide
preparations
Sulfuryl
fluoride
None Non-corrosive Discharged from
cylinders
10/2002-04 Treatment Manual 2-3-1
PPQ
Treatment Manual
2 Chemical Treatments 3
Fumigants • Methyl Bromide
Contents
Properties and Use page-2-3-1
“Q Labels” and Section 18 Exemption Treatment Schedules page-2-3-2
Leak Detection and Gas Analysis page-2-3-4
Effects of Temperature and Humidity page-2-3-4
Penetration and Aeration of Boxes and Packages page-2-3-5
Plastic Wrappings and Impermeable Papers page-2-3-5
Kraft Paper and Corrugated Cartons page-2-3-5
Wooden Boxes page-2-3-5
Sorption page-2-3-5
Residual Effect page-2-3-6
 
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