曝光台 注意防骗
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The fumigation time begins once all the gas has been introduced.
Record the time gas introduction was started and completed in Block
32 on the PPQ Form 429. Run the fans for 30 minutes after all gas has
been introduced. You will take the initial concentration reading 30
minutes after all the gas has been introduced.
When using large cylinders, getting the final amount of gas out of the
cylinder may take a long time. Using a pressurized cylinder will
shorten the time. Consider taking a T/C unit reading 30 minutes after
the gas was first introduced. If the gas distribution is even (all
readings within 4 ounces of each other) and at a sufficiently high
concentration, then turn off the fans. Running the fans longer may
contribute to gas leakage. Allow the remainder of the gas to discharge
at its slow rate with intermittent running of the fans for dispersal.
You and the fumigator must wear the SCBA whenever:
◆ Concentration exceeds 5 ppm
◆ The concentration level is unknown, as with spills, leaks, and other
emergencies
◆ Introducting gas
◆ Checking for leaks
◆ Taking aeration readings
In addition, the PPQ Officer must wear SCBA when they are within 30 feet of
the enclosure.
Do not touch the introduction line with your bare hands—you may get burned!
Close the cylinder valve once the proper dosage has been introduced.
Chemical Treatments Fumigants • Methyl Bromide • Structure Fumigation
Conducting the Fumigation
2-7-14 Treatment Manual 10/2002-04
PPQ
Step 2—Testing for Leaks
Wear the SCBA while checking for leaks. Use a halide detector to test
for leaks before the 30 minute reading. Test around the perimeter of
the tarpaulin on the ground, corners, and especially where electric
cords, gas sampling tubes, or gas introduction lines are present. If you
detect leaks, be sure they are sealed by using more sand or water
snakes for floor leaks and tape for small holes in the tarpaulin.
Step 3—Taking Concentration Readings
Take concentration readings with a T/C unit to determine the gas
concentration and distribution within the enclosure. Check Drierite®
tubes before each reading and change Drierite® if its color is pink.
Depending upon the length of exposure period, take concentration
readings at the following times after the introduction of the fumigant:
◆ 30 minutes
◆ 2 hours
◆ 4 hours
◆ 6 hours
◆ 12 hours
◆ 24 hours
◆ 36 hours
◆ 48 hours
◆ 72 hours
All times are after gas introduction is completed.
Use an auxiliary air pump when there are many gas sampling tubes or
the gas sampling tubes are very long. The auxiliary air pump will
lessen the time required to draw gas to the T/C unit.
You may start the final reading 30 minutes to 1 hour prior to
completion of the exposure period. If final gas concentration levels
meet minimum levels, start aeration immediately at the end of the
exposure period.
Additional
Readings
Adverse weather conditions may indicate the need for additional
readings. Sorptive commodities and indications of a steady decline in
gas concentration also indicate the need to take additional
concentration readings.
Step 4—Adding Gas
For concentration readings below minimum levels, add gas at the
following rate:
1.6 × number of oz. below × volume/1,000 = oz. of fumigant to add
Chemical Treatments Fumigants • Methyl Bromide • Structure Fumigation
Aerating the Enclosure
10/2002-04 Treatment Manual 2-7-15
PPQ
Once you’ve determined that you need to add gas, follow the same
procedures as introducing the gas (Step 1). That is—
1. Heat water in the volatilizer to at least 200 °F.
2. Turn on the fans.
3. Weigh the cylinder.
4. Use your SCBA.
5. Open valve on cylinder and introduce the gas.
6. Close valve when the weight of the cylinder indicates that the
needed amount of gas has been added.
7. Record quantity of fumigant added in Block 34 on the PPQ Form
429.
Note the time you started introducing additional gas and the time you
finished introducing gas and record in Block 40 (Remarks) on the PPQ
Form 429. Run the fans until you get even gas distribution throughout
the enclosure. Turn off the fans, then take a concentration reading 30
minutes after you complete introducing the gas. If all readings are
above minimum concentration levels, then proceed as usual with the
remainder of the concentration readings. If gas is not evenly
distributed (readings not within 4 oz. of each other), then run fans
until you get gas evenly distributed.
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