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Peter Witherell
USDA-APHIS-PPQ-CPHST
Treatment Support & Certification
1017 Main Campus Drive, Suite 2500
Raleigh, NC 27606
tel: 919-513-2496, ext. 236
Request for certification can be sent to State Plant Directors listed at the
following URL:
http://www.aphis.usda.gov/travel/aqi.html
Certifying Facilities Overview
Contents
6-1-2 Treatment Manual 10/2002-04
PPQ
Important
Blueprints or drawings and request for certification of foreign treatment
facilities should be sent to:
David Reeves
Director, Preclearance Programs
USDA, APHIS, PPQ
4700 River Road, Unit 60
Riverdale, MD 20737
tel: 301-734-8295
fax: 301-734-8318
For foreign treatment facilities, the company requesting certification is
responsible for paying money into a trust fund account to pay the salary, travel
costs, and per diem of a PPQ Officer to be sent on temporary duty.
Sea-going vessels that participate in the APHIS cold treatment program for
fresh fruit may be certified at a port in the USA or at a foreign port. Also, if the
certification is to be carried out overseas, a trust fund account will be needed
to cover the costs. (For details call Stephanie Hyatt, PPQ Quarantine Policy,
Analysis and Support (QPAS), tel: 301-734-6404.
10/2002-04 Treatment Manual 6-2-1
PPQ
Treatment Manual
6 Certifying Facilities 1
Certification of Vacuum Fumigation
Chambers
Contents
Construction and Performance Standards page-6-2-1
Chamber page-6-2-1
Vacuum Pump page-6-2-2
Fumigant Introduction Systems page-6-2-2
Circulation and Exhaust System page-6-2-2
Accessories page-6-2-3
Performance Standards page-6-2-3
Construction and Performance Standards
Fumigation by vacuum consists of placing the commodity in a
gas-tight steel chamber, removing most of the air, and replacing a
small portion of it with a gas which is lethal to insects and other pests.
Vacuum fumigation provides a more rapid penetration of commodities
undergoing treatment than is obtained in atmospheric fumigations.
The length of exposure in vacuum fumigation may range from 2 to 4
hours as compared with 12 to 24 hours under atmospheric
conditions.
Chamber
Vacuum chambers are usually of welded steel construction. A
rectangular chamber may be preferred for more effective use of space.
Reinforcement of the chamber body by means of steel ribs, or other
supports, is usually required to enable the chamber to withstand the
difference in pressures when the vacuum is drawn. Doors may be
provided at one or both ends of the chamber. In cylindrical chambers,
the doors may be either concave or convex, but in rectangular
chambers flat doors are commonly used with suitable reinforcements.
The doors may be hinged at the side, or at the top and
counterbalanced. Many doors are fitted with special mechanisms for
rapid closing. Door gaskets should be durable and at the same time
provide gas-tight seal. The efficiency of a chamber depends to a large
extent upon the tightness with which the door or doors will seal. All
other chamber openings must be equally tight to sustain the
prescribed vacuum over a specified period of time.
Certifying Facilities Certification of Vacuum Fumigation Chambers
Construction and Performance Standards
6-2-2 Treatment Manual 10/2002-04
PPQ
To permit circulation beneath the load, the chamber must be designed
to enable the loading of commodities stacked on pallets, skids, or
small trucks. Small chambers which are usually hand loaded should
be provided with removable floors.
Vacuum Pump
Each installation required a high quality, high capacity vacuum
pump. The vacuum pump should have the capacity to reduce the
chamber pressure to 1–2 inches (25–51 mm) of mercury (28–29 inch
or 711–737 mm vacuum) in 15 minutes or less.
Fumigant Introduction Systems
The introduction system needed will vary with the type of fumigant in
use and the size of the chamber. For small chambers and for
introducing fumigants in small quantities, the fumigant may be
measured by volume using a graduated dispenser. For larger
chambers the gas supply cylinder is placed on a platform scale and
the amount of fumigant required is measured by weight.
For most fumigants, a volatilizing unit is required to insure fumigant
introduction in a gaseous state. The volatilizer is located outside of the
chamber between the gas cylinder or dispenser and the introduction
port of the chamber. The volatilizer consists essentially of a metal coil
submerged in water which is kept hot enough to vaporize the
　
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