United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-94/170 September 1994
Project Summary
Electronic Component Cooling
Alternatives: Compressed Air
and Liquid Nitrogen
Stephen C. Schmitt and Robert F. Olfenbuttel
The goal of this study was to evalu-
ate tools used to troubleshoot elec-
tronic circuit boards with known or
suspected thermally intermittent failure
modes. Aerosol cans of refrigerants,
which are commonly used in electron-
ics manufacturing and repair busi-
nesses for this purpose, served as the
benchmark for the evaluation.
One promising alternative technology
evaluated in this study is a com-
pressed-air tool that provides a con-
tinuous stream of cold air that can be
directed toward specific components.
Another alternative technology that was
considered is a Dewar flask that dis-
penses cold nitrogen gas as the cool-
ing agent. Critical parameters were
measured for each cooling method to
provide a basis for comparing com-
pressed air and liquid nitrogen with
spray cans of refrigerant. These pa-
rameters are accuracy, electrostatic dis-
charge risk, cooling capability,
technician safety, pollution prevention
potential, and economic viability.
Newark Air Force Base (NAFB), in
Ohio, was the site at which com-
pressed-air and liquid-nitrogen tech-
nologies were evaluated. The electronic
circuit boards that are tested and re-
paired daily at NAFB come from a vari-
ety of Air Force Systems, such as
inertial guidance systems used in KC-
135, C-5, and C-141 aircraft and a fuel-
saver advisory system used in the
KC-135. A percentage of these circuit
boards demonstrate thermally intermit-
tent failure modes and were used for
comparison testing. Both alternative
cooling technologies performed suffi-
ciently well to be considered for use in
trouble-shooting circuit boards. Both
reduced pollution and cost less than
aerosol refrigerants typically used.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
The objective of the U.S. Environmental
Protection Agency (EPA) Waste Reduc-
tion Innovative Technology Evaluation
(WRITE) Program is to evaluate, in a typi-
cal workplace environment, examples of
prototype technologies that have potential
for reducing wastes at the source or for
preventing pollution. In general, for each
technology to be evaluated, three issues
should be addressed.
First, it must be determined whether the
technology is effective. Because pollution
prevention or waste reduction technolo-
gies usually involve recycling or reusing
materials or using substitute materials or
techniques, it is important to verify that
the quality of the materials and the quality
of the work product are satisfactory for
the intended purpose.
Printed on Recycled Paper
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Second, it must be demonstrated that
using the technology has a measurable
positive effect on reducing waste or pre-
venting pollution.
Third, the economics of the new tech-
nology must be quantified and compared
with the economics of the existing tech-
nology. It should be clear, however, that
improved economics is not an absolute
criterion for the use of the prototype tech-
nology. There may be justifications other
than saving money that would encourage
adoption of new operating approaches.
Nonetheless, information about the eco-
nomic implications of any such potential
change is useful for understanding the
overall effect of implementation.
This study evaluated the use of cold
compressed-air tools and liquid nitrogen
as methods for cooling electronic circuits
while searching for causes of thermally
intermittent circuit failures. Aerosol cans
of refrigerant (i.e., CFC R-12 and HCFC
R-22), which commonly have been used
in electronics manufacturing and repair
businesses for this purpose, served as
the benchmark for the evaluation. Six criti-
cal parameters were measured for each
cooling method: accuracy, electrostatic dis-
charge risk, cooling capability, technician
safety, pollution prevention potential, and
economics. The first three parameters are
related to product quality, i.e., the accu-
racy with which circuit board failures can
be located, and are discussed in that sec-
tion. The remaining parameters are dis-
cussed independently.
Description of the Technology
Aerosol cans of refrigerant, such as R-
12 and R-22, are commonly used in the
electronics manufacturing and repair in-
dustries for trouble-shooting circuit boards
that have known or suspected thermally
intermittent failure modes. Thermally in-
termittent failures occur when tempera-
ture changes and material expansion or
contraction aggravate the mechanical fail-
ure to create an electrical discontinuity
condition. For example, if an electronic
device works when first turned on but fails
as it warms up in operation, a technician
may spray refrigerant towards board ar-
eas or on specific components to reduce
temperatures until the device begins to
work again. The component that, when
cooled, causes the failure mode to appear
or disappear is replaced. If the circuit fail-
ure mode still exists, the troubleshooting
process is repeated.
Aerosol cans of refrigerant are com-
monly used as trouble-shooting tools. They
can be used easily to cool an entire circuit
board or a single solder connection and
are portable and relatively inexpensive.
As recognized in the Montreal Protocol of
1987, however, chlorine released by de-
composing chlorofluorocarbons (CFCs),
such as R-12, decreases stratospheric
ozone. The protocol calls for the elimina-
tion of CFC manufacture in the future. As
a result, many businesses are seeking
technologies that will replace current uses
of CFCs. Hydrochlorofluoro-carbons
(HCFCs), such as R-22, also will be
phased out, although they have lower
stratospheric ozone-depleting potential.
The first alternative technology evalu-
ated was a compressed-air tool that pro-
vides a continuous stream of cold air that
can be directed towards components.
Compressed air enters a tangentially drilled
stationary generator which forces the air
to spin down the long tube's inner walls
toward the hot-air control valve. A per-
centage of the air, now at atmospheric
pressure, exits through the needle valve
at the hot-air exhaust. The remaining air
is forced back through the center of the
sonic-velocity airstream where, still spin-
ning, it moves at a slower speed, causing
a simple heat exchange to take place.
The inner, slower-moving air gives up heat
to the outer, faster-moving air column.
When the slower inner air column exits
through the center of the stationary gen-
erator and out the cold exhaust, it has
reached an extremely low temperature.
To obtain temperatures in the range of
-35°C to -40°C, the tool requires clean,
dry, room-temperature air flowing at 15
scfm at 100 psi pressure.
The second alternative technology
evaluated uses liquid nitrogen. A 1/2-L
Dewar flask can be used with a release
valve that allows a stream of nitrogen gas
and liquid droplets to be directed through
a small-diameter stainless-steel nozzle. As
the valve and nozzle are cooled by the
nitrogen flow, the portion of the stream
that is droplets increases and the output
stream drops in temperature. A variety of
valves, nozzles, and heat exchangers are
available to tailor the delivery and cooling
characteristics of the stream of nitrogen.
The Dewar flask can be refilled from a
bulk container of liquid nitrogen.
Description of the Site
Newark AFB (NAFB) was the site at
which compressed-air and liquid-nitrogen
alternative technologies were evaluated.
Electronic circuit boards from a variety of
Air Force systems, such as inertial guid-
ance systems, are tested and repaired at
NAFB daily. A percentage of the tested
circuit boards demonstrate thermally inter-
mittent failure modes; during the test pe-
riod, these boards became test articles for
comparison testing. R-12 was used for
this study as the benchmark.
Each repair shop at NAFB is respon-
sible for specific systems. Because com-
pressed air is not typically available at the
test stations where cooling materials are
needed, it was necessary to select one
shop for the study. After evaluating sev-
eral shops, the Carousel Shop was se-
lected as the test site because:
• The test stations included fixtures that
were capable of reducing circuit board
temperature (using carbon dioxide)
while the board is tested. This feature
provided confirmation that thermally
intermittent failure mode existed but
did not provide a troubleshooting
capability since the entire board was
cooled at one time.
• The systems repaired in the Carousel
shop contained circuit boards in a
variety of sizes, component densities,
and component varieties.
• Installation costs to deliver
compressed air could be minimized
because the three test stations used
for the study are in close proximity.
The compressed-air system used for
the study consisted of a large industrial
compressor with a refrigeration system to
chill the compressed air as it passed into
a storage tank. The air passed through
approximately 50 ft of 1/2-in. line with
nonrestrictive couplings to three outlets. A
filtration and drying system was installed
approximately 20 ft from the test stations.
A 5-hp compressor is the minimum re-
quirement for continuous operation of an
air tool.
Product Quality Evaluation
Three factors determine how well a
given cooling method will work to identify
failing circuit board components: accuracy,
electrostatic discharge risk, and the cool-
ing rate and absolute temperature drop.
The procedures used to evaluate these
factors and the conclusions reached dur-
ing this study are described briefly below;
additional detail is provided in the final
report.
Accuracy
For this project, accuracy was defined
as the capability of a technician using a
cooling method to identify a specific com-
ponent with a thermally intermittent failure
mode causing a circuit board to have a
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thermally intermittent circuit failure mode.
An accurate cooling method provides a
high component identification confidence
(CIC) level, which avoids the cost of erro-
neously replacing nondefective compo-
nents, potential damage created during
component replacement, and multiple it-
erations of testing and repair.
An experiment was performed to com-
pare the capability of each cooling method
to identify components with thermally in-
termittent failure modes. During the 5-
month test period, 17 circuit boards were
identified initially as having thermally in-
termittent failure modes. Four of these
were subsequently removed from the
evaluation because they were found not
to be thermally intermittent or because
the defective components were known
from previous experience with a specific
model circuit board. Each of the remain-
ing 13 test articles were evaluated with
the use of each of the three cooling meth-
ods. Three technicians, working indepen-
dently of each other, evaluated the test
articles following a randomized sequence
of cooling methods. For each evaluation,
the technicians assigned a CIC level which
reflected their confidence that they had
been able to isolate the cause of the cir-
cuit failure using the assigned cooling
method.
The number and variety of test articles
identified during the test period were not
as great as hoped for. Also, the results of
the test article evaluations do not support
comparisons of the accuracy of the cool-
ing methods. However, the results do in-
dicate that the compressed-air method was
able to reproduce circuit failures in 12 of
13 test articles. This is significant because
it is known that the cooling capability of
compressed air is less than either refrig-
erants or liquid nitrogen.
Also, a potential problem related to liq-
uid nitrogen temperatures may have been
identified — for one test article, the very
low temperature apparently caused a RAM
chip to fail temporarily, masking the diode
that was the actual defective component.
Potential users of liquid nitrogen may want
to consider temperature control strategies
to avoid excessively low temperatures that
could temporarily change component func-
tions or even damage components; pos-
sible strategies are discussed in an
appendix to the report.
Detailed accuracy evaluation results are
provided in the final report, including pho-
tographs of each test article and, if avail-
able, the results of the component
replacement and retesting. This informa-
tion is expected to help potential users of
the alternative cooling materials determine
the applicability of study results to their
operations.
Electrostatic Discharge Risk
The amount of electrostatic charge
buildup generated by the cooling material
as it is dispensed is a concern because
components can be damaged by electro-
static discharge. Two experiments were
designed to compare the electrostatic
charge generated by the following cooling
method/nozzle combinations:
• R-12 aerosol with a plastic tube nozzle
• R-12 aerosol with a steel tube nozzle
• compressed-air tool with a single-
section plastic nozzle
• liquid nitrogen Dewar flask with a
straight stainless-steel nozzle
approximately 4-in. long
The first experiment measured the elec-
trostatic charge generated on the nozzle
during release of cooling material. During
a 10- to 12-sec material release, the nozzle
was held parallel to and approximately 1
in. from the platen of an Ion Systems,
Inc., Model 200 Charged Platen Monitor*,
which measured charge buildup. Two mea-
surements were taken for each cooling
method/nozzle combination.
The second experiment measured elec-
trostatic charge buildup when cooling ma-
terial was dispensed toward circuit boards
placed on the platen of an Ion Systems
Model 200 Charged Platen Monitor. The
dispenser was held so that the nozzle
was approximately 0.5 in. from the edge
of the circuit board, both horizontally and
vertically, and at approximately 45 degrees
relative to the horizontal surface of the
circuit board. Six circuit boards were evalu-
ated, with two measurements taken for
each cooling method/nozzle combination.
The six circuit boards were selected to
provide component and density variety.
Averages of each pair of measurements
indicate that both the compressed air and
the liquid nitrogen alternatives generated
lower electrostatic charge buildup than did
R-12 through either plastic or steel nozzles.
Thus, the risk of electrostatic charge
buildup is not increased by using either of
the alternative component cooling tech-
nologies. If aerosol cans of R-12 have
been used successfully, either compressed
air or liquid nitrogen should be acceptable
alternatives.
Mention of trade names or commercial products does
not constitute endorsement or recommendation for
use.
Cooling Rate and Absolute
Temperature Drop
Cooling rate and absolute temperature
drop were measured for each method.
Understanding the characteristics of and
differences between cooling methods will
enable technicians to use the compressed-
air and liquid nitrogen technologies effec-
tively. For example, the distance between
the applicator nozzle and the component
does not significantly affect the cooling
rate of aerosol cans of R-12; this distance
is, however, expected to be a significant
factor in the cooling rate provided by com-
pressed air.
An experiment was designed to esti-
mate the rate of change of component
temperature. Two test boards were fabri-
cated, one having integrated circuits and
the other having wound-film capacitors.
Each test board contained three compo-
nents with thermocouples buried inside
and one exposed thermocouple. During
tests, all four thermocouples on a test
board were connected to a Yokogawa
LR4110 four-channel data logger, which
simultaneously recorded temperatures of
all four thermocouples as cooling material
was directed at the target component. For
each test board, cooling material was ap-
plied from two directions and two dis-
tances. Two measurements were taken
for each combination of test board, cool-
ing method, direction, and distance. Be-
fore each measurement for R-12 and
compressed air, the cooling material was
dispensed directly at the exposed thermo-
couple to determine the absolute lowest
temperature that could be achieved given
the test distance, direction, and cooling
method. This was not necessary for liquid
nitrogen because it was known that the
thermocouple would reach the lowest mea-
surement limit of -175°C. Table 1 shows
the temperatures achieved under one set
of conditions.
In all tests, the cooling material dis-
pensers were positioned and aimed manu-
ally. By using visual feedback from the
data logger chart to determine when a
stable minimum temperature was reached,
the technician adjusted the angle of el-
evation slightly to ensure that minimum
temperatures were obtained for each ap-
plication direction and distance. Different
angles of elevation undersprayed or
oversprayed the cooling material, thus
changing the cooling rate and the differ-
ence in temperature between the target
component and other components on the
test fixtures. As a result, the absolute tem-
perature drop data presented are used for
direct comparison of cooling materials; but
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Table 1. Minimum Temperature Achieved (at 1/4-in. Distance) and Elapsed Time for Three Cooling Points
Aerosol R-12
Compressed Air
Liquid Nitrogen
Component
Type/Test
Integrated Circuit
Target Component
Exposed Thermocouple
Wound-Film Capacitor
Target Component
Exposed Thermocouple
Temperature
(°C)
-45.0
-54.5
-53.5
-59.5
Elapsed Time
(sec)
18.0
—
77.5
—
Temperature
(°C)
-27.5
-35.5
-11.5
-35.0
Elapsed Time
(sec)
29.0
—
121.0
—
Temperature
(°C)
-175.0
-175.0
-134.0
-175.0*
Elapsed Time
(sec)
31.0
—
51.0
—
* Minimum thermocouple temperature assumed to be — 175°C based on wound-film capacitor tests.
100 _
o
I
I
.5
o -
-100 -
-200
Compressed air
R-12
Elapsed time (seconds)
Figure 1. Typical cooling rate comparison for integrated circuits: distance 1/4-in.
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cooling rate and temperature difference
data, while they indicate performance that
may be obtained in actual use, are not
used for direct comparisons. The cooling
rates of the three methods under one set
of conditions are compared in Figure 1.
The three cooling materials differed in
how they cooled components. As R-12
was sprayed towards components, it built
up a "slush" on and around the compo-
nent. When the spray of R-12 was stopped,
the slush continued to evaporate and lower
the component temperature even further.
The fastest initial cooling rates were ob-
tained with R-12, although the cooling rate
decreased as component temperature
dropped. Liquid nitrogen provided the cold-
est temperatures of the three cooling ma-
terials. In contrast to R-12, an accelerating
cooling rate was obtained when liquid ni-
trogen was used. The cooling material
consists of nitrogen gas and droplets of
liquid nitrogen; as the dispensing valve
and nozzle cools, the proportion of drop-
lets increases. The increase in droplets
could be heard as increased "sputtering"
of cooling material during material release.
Frost buildup on the components during
cooling was minimal. Compressed air pro-
vided the least cold temperatures and the
slowest cooling rate. As with R-12, the
cooling rate decreased as component tem-
perature dropped. Compressed-air cool-
ing resulted in a slight frost buildup on the
components.
The three cooling methods differed also
in their sensitivity to such parameters as
component type, application distance, and
application direction. Evaluation of mini-
mum target component temperature data
indicates that:
• Component type is affected by the
sensitivity of the liquid nitrogen and
of the compressed air, both of which
provided lower temperatures with
integrated circuits than with the
wound-film capacitors. R-12 was not
significantly sensitive to the type of
component and provided minimum
temperatures for capacitors and
integrated circuits that were not
significantly different under each
application distance/direction
combination.
• Distance from the target component
affects the component cooling
capabilities of both compressed air
and liquid nitrogen. An examination
of the temperature data summarized
in the final report reveals that, as the
distance from the component to the
nozzle increased from 0.25 in. to 1
in., the minimum component
temperature decreased for both
alternative methods. This relationship
does not exist for R-12, indicating that
it is not as sensitive to distance.
• A comparison of component minimum
temperature data for two different
directions of application indicates that
R-12 is not sensitive to application
direction. In contrast, compressed air
provided lower component
temperatures for integrated circuits,
but liquid nitrogen yielded lower
component temperatures for wound-
film capacitors. The most likely
explanation of this difference is the
variability resulting from manual
positioning of the dispensers.
Technician Safety
Exposure to sound created by opera-
tion of the compressed-air tool was a
safety concern. To assess the potential
safety hazard, personnel from the Newark
AFB Bioenvironmental Engineering Office
took sound-level measurements during
operation of the compressed-air tool. A
sound level of 81 dBA was recorded at
the operator work position. Because the
sound levels did not exceed 84 dBA, ad-
ditional measurement was not required by
the Air Force and, in accordance with Air
Force Regulation 161-35, hearing conser-
vation precautions were deemed unnec-
essary.
The safety concerns related to handling
liquid nitrogen and aerosols are well-
known. Therefore, no technician safety
testing was required.
Pollution Prevention Potential
The purpose of replacing aerosol cans
of refrigerant is to reduce the amount of
pollutants released into the atmosphere.
During the accuracy experiments, the
weight of R-12 released during evaluation
of each.circuit board with thermally inter-
mittent failure modes was determined. The
procedures for collecting these data are
described in the project report.
These data provide a measure of the
average pollution per circuit board that
could be prevented if either of the alterna-
tive cooling methods were adopted in place
of R-12. The average R-12 release/article
was 232.65 g (0.51 Ib). With the adoption
of either alternative technology, release of
R-12 would be eliminated along with the
wastestream of empty aerosol cans. Nei-
ther usage nor production information for
the United States was available when this
report was written; quantities consumed
vary by user, ranging from a few cans/ mo
in repair shops to over a thousand cans/yr
in production operations.
Economics Evaluation
To ass.ess the economics of replacing
R-12 use with either of the alternative
technologies, operating costs and invest-
ment costs were examined.
The approach to estimating operating
costs was to measure the volume of each
cooling material used during test article
accuracy evaluations and calculate a per-
board material cost. Although material
costs are only one aspect of operating
costs, it was the only aspect that could be
measured during the tests. It was beyond
the scope of this study to measure all
potential effects of alternative component-
cooling materials on operating costs, par-
ticularly those for direct labor and
materials. If an alternative cooling mate-
rial is less able to isolate the specific com-
ponent causing a thermally intermittent
circuit, components may be replaced un-
necessarily. Each component replacement
adds cost in the form of direct labor for
replacement and retesting, component
costs, and risk of circuit board damage. If
a cooling method is unable to identify the
defective component, a circuit board may
be condemned unnecessarily. Compari-
sons of the ability of the various cooling
materials to isolate thermally intermittent
components was addressed in the discus-
sions of accuracy and absolute tempera-
ture drop/cooling rate above.
Cooling Material Costs
Cooling material costs are based on the
use data collected during the accuracy
evaluation of the 13 test articles. The meth-
odologies for collecting the data and cal-
culating the use are described in detail in
the project report. Use data were con-
verted to cost data as follows:
• R-12 cost was based on a cost of
$7.50/16-oz aerosol can. Purchase
price of R-12 or R-22 freeze
compound ranges from $6 to $157
can; $7.50 was selected as a
conservative estimate.
• Compressed-air cost was calculated
by using an air tool consumption rate
of 15 cfm at 100 psi and an estimated
compressed-air generation cost of
$0.26/1000 ft3. The generation cost
will vary based on power costs and
other factors and should be verified
by potential users.
• Purchase cost of liquid nitrogen varies
widely; $0.25/L was used as a typical
cost. Potential users should obtain
price quotations from local suppliers.
Investment Costs
The approach to estimating investment
cost focused on the cost of dispensers.
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There is no such investment exist for R-
12. Costs for the alternative cooling mate-
rial dispensing equipment are discussed
below.
For compressed air, investment cost is
expected to range widely because the con-
dition and capacity of existing compressed-
air supplies at test stations will vary widely.
Some sites may not have an existing air
supply. Potential users will need to deter-
mine what, if any, investment is needed to
obtain compressed air in the quantities
and quality required. Implementation of
compressed air requires, at a minimum,
investment in the air tools at approximately
$200/unit. The investment required to gen-
erate and deliver 15 scfm at 100 psi to the
tools at a work position will vary with each
potential user. If no compressed air is
available in a shop, the minimum equip-
ment required to supply one air tool is a
5-hp compressor, oil-filter and desiccant
filters, and nonrestrictive air lines, con-
nectors, and valves. Purchase and instal-
lation costs also will vary for each potential
user.
Implementation of liquid nitrogen would
require approximately $500 for each 1/2-L
Dewar flask. Heat exchangers or other
accessories would be additional. Cylin-
ders for bulk liquid nitrogen generally are
provided by the suppliers at no charge. If
use rate is low, suppliers may require a
leasing arrangement for the bulk contain-
ers.
Economics Assessment
Data presented in the project report in-
dicate that a material cost savings of $5.287
circuit board can be projected if testing is
done with liquid nitrogen instead of R-12.
This would result in payback of a $500
dispenser investment after 95 circuit
boards have been tested.
For a shop that has an existing ad-
equate air supply, the average operating
cost savings for compressed air is $5.267
board. This would pay back a $200 air-
tool investment after 38 circuit boards have
been tested. The payback period would
be extended if additional investment were
required to compress and deliver air to
the work positions.
Table 2 summarizes investment and
payback figures for each alternative tech-
nology.
Discussion
The objective of this study was to char-
acterize and compare the use of aerosol
cans of refrigerant, compressed air, and
Table 2. Investment Cost and Payback
Cooling Method
Investment
Payback
(circuit boards tested)
Compressed Air
Liquid Nitrogen
$200
$500
38
95
liquid nitrogen as methods to cool elec-
tronic circuits during troubleshooting. Data
obtained from testing were used to com-
pare the alternative cooling methods in
terms of accuracy, electrostatic discharge
risk, cooling performance, technician safety
hazards, pollution prevention potential, and
economics. Interpretation of the results of
this study are:
• The compressed-air tool evaluated
during the study was unable to cool
components to the temperature level
that was obtained with either R-12 or
liquid nitrogen. The results of the
accuracy test, however, indicate that
during all but one test, temperatures
achieved with the compressed-air tool
were low enough to reproduce circuit
failures.
• Liquid nitrogen has the capability to
readily cool components to below -
175°C if dispensed closely enough.
At such temperatures, components
may fail from temporary changes in
output signals or fail permanently from
physical damage. Two methods to
control the temperature of components
are to maintain dispensing nozzle
distance and to slow the cooling rate
of the dispenser by adding heat
exchangers or smaller orifices. Both
methods rely on technician skill to a
greater extent than do either
compressed air or R-12. Further
discussion of component temperature
control with liquid nitrogen is provided
in an appendix to the project report.
• The results of the accuracy
experiment do not support conclusions
regarding the relative effectiveness of
alternative cooling methods and
aerosol cans of refrigerant.
• Neither alternative is expected to
increase safety risks to technicians
when compared with those of aerosol
refrigerants. Noise levels are higher
during compressed-air tool operation
than with R-12 or liquid nitrogen, but
they are not high enough to pose a
health hazard to users. Handling of
liquid nitrogen presents a safety risk
in the form of exposure to low
temperatures, but technician training
and proper safety procedures and
equipment are expected to reduce risk
to acceptable levels. As with any
aerosol, release of refrigerants under
pressure presents a safety risk that is
minimized through training.
• Replacement of aerosol refrigerant
prevents emissions of substances that
deplete the stratospheric ozone layer
as well as accumulation of empty
aerosol cans requiring landfill disposal.
With liquid nitrogen, only nitrogen is
emitted and refillable bulk containers
and dispensers are used.
Compressed air generates a small
amount of pollution in the forms of
waste compressor oil and filter
elements, but the incremental increase
in these wastestreams that would
follow adoption of the compressed-air
method is not expected to be
significant.
• Material costs of either alternative are
expected to be lower than those of R-
12 or R-22 at current prices. Prices of
R-12 and R-22 will undoubtedly
escalate and, eventually, these
materials will be unavailable due to
regulatory prohibition.
• Investment cost to implement liquid
nitrogen is expected to consist of the
price of Dewar flask dispensers at
approximately $500 each in the 1/2-L
size. Compressed-air tools cost
approximately $200 each. The cost
of equipment to deliver compressed
air that is clean, dry, and near room
temperature in the volume and
pressure required to achieve
maximum cooling capability will
depend on existing equipment and
the number of tools to be used.
The full report was submitted in fulfill-
ment of Contract No. 68-CO-0003, Work
Assignment No. 2-36, by Battelle under
the sponsorship of the U.S. Environmen-
tal Protection Agency.
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Stephen Schmitt and Robert Olfenbuttel are with Batelle Memorial Institute
Columbus, OH 43201-2693
Johnny Springer, Jr., is the EPA Project Officer (see below).
The complete report, entitled "Electronic Component Cooling Alternatives:
Compressed Air and Liquid Nitrogen," (Order No. PB95-100087/AS;
Cost: $27.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-94/170
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