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fumigant. If more than one fumigant will be used in the chamber, a
separate volatilizer and gas introduction line should be used for each
in order to reduce the possibility of corrosion or formation of
precipitates.
Within the chamber the gas introduction system should consist of
tubing with multiple graduated openings which will provide uniform
distribution of the fumigant throughout the length of the chamber.
The tubing shall be installed along the ceiling.
Circulation and Exhaust System
Adequate distribution of the gas is often hindered by the cargo placed
in the chamber. To overcome this, vacuum chambers should be
equipped with a circulatory system. If fans are employed, the number
of fans required would depend upon the chamber design, volume, and
loading arrangements. A minimum of two would normally be required
for chambers of over 1,000 cu ft capacity (28.31 m3). The fans are to be
placed at opposite ends of the chamber facing each other—one high,
one low. Additional fans may be required for larger chambers. Their
combined capacity should be such that they are capable of moving
each minute a volume of air which is equal to approximately one-third
the volume of the chamber. Non-sparking, explosion-proof type
circulation systems are required with some fumigants.
Certifying Facilities Certification of Vacuum Fumigation Chambers
Construction and Performance Standards
10/2002-04 Treatment Manual 6-2-3
PPQ
In most installations, the vacuum pump is used to remove the
fumigant following the exposure period. The air-gas mixture is
pumped out of the chamber through exhaust ducts or stacks installed
for that purpose. The actual height of these stacks will vary with the
location of the chamber, and may be regulated by local safety
ordinances.
Accessories
Chambers must be equipped with a vacuum gauge and an instrument
for measuring and recording the vacuum drawn and maintained
during the exposure period. A temperature instrument must be
installed in chambers used for quarantine treatments with long
exposure periods. Combination temperature and vacuum recorders
are available.
Performance Standards
To qualify for program approval, vacuum chambers must be able to
meet or exceed specified vacuum leakage tests. The tests are listed
below and determine the classification under which the chamber
qualified.
In addition, ALL chambers must be capable of meeting the following
requirement: A vacuum equivalent to 26 inches (660 mm) of mercury
is drawn. The vacuum is then reduced to 5 inches (127 mm) and held
for a period of 4 hours. A vacuum of 2 inches (55 mm) or more after 4
hours is considered adequate for this test.
Chambers classified “Superior” or “A” are approved for all vacuum
treatments. These chambers are to be tested annually.
Chambers classified “B” are approved for all vacuum schedules up to
and including 28-inch (711 mm) sustained vacuum. These chambers
are to be tested semiannually.
Approval of a chamber for vacuum fumigation does not include
approval for atmospheric (NAP) fumigations. If the vacuum chamber
will also be used as a normal atmospheric pressure chamber, then it
must also pass a pressure leakage test (see page-2-5-6).
Classification
Initial vacuum
equivalent to inches
of mercury
Allowable vacuum loss
4 hr 6 hr 16 hr 24 hr
Superior 28 1/2 — 1/2” — 1"
A 28 1/2 1/2” — 1" 2"
B 28 1/2 1" — 2 1/2” 3"
C 26 1" — 2 1/2” 3"
Certifying Facilities Certification of Vacuum Fumigation Chambers
Construction and Performance Standards
6-2-4 Treatment Manual 10/2002-04
PPQ
Actual detailed instructions for constructing a vacuum chamber are
not included in this discussion. The information presented is designed
to list the component parts that are needed in the chamber and the
function of each. Instructions and additional information can be
obtained from the following list of vacuum chamber manufacturers. In
furnishing the names of these dealers, no discrimination is intended
against any firm whose name may have been omitted. Neither does
this program endorse the firms mentioned nor guarantee the reliability
of their products. The list is furnished solely for information and
convenience.
Partial List of Manufacturers of Vacuum Chambers
Cos-Med Group
(a.k.a. ETO Sterilization, Inc.)
250 Brunswick Avenue
Linden, NJ 07036
Slack Associates, Inc.
540 South Longwood Street
Baltimore, MD 21223
Vacudyne Altair
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