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United States
EnvironmlWWProtection
Agency
Air and Energy Engineering *^M^>>
Research Laboratory x V \N
Research Triangle Park NC 27711 "
EPA/600/S2-89/009 June 1989
v°/EPA Project Summary
Evaluation of Refrigerant from
Mobile Air Conditioners
Leo Weitzman
This project was initiated to provide
a scientific basis for choosing a
reasonable standard of purity for
recycled chloroflurocarbon (CFC)
refrigerant in operating automobile
air conditioners. It evaluated the
quality of the refrigerant from air
conditioners in automobiles of
different makes, ages, and mileages,
from different parts of the country,
and with both failed and properly
working air conditioners. The
refrigerant, CFC-12, was tested for
water content, acidity, residue
quantity, refrigerant purity, residue
purity, inorganic chloride, and
inorganic fluoride. This work will be
the basis for programs to reduce CFC
emissions from the servicing of
automotive air conditioners.
Of the 227 cars sampled, neither
the compressor oil nor the refrigerant
showed any measurable levels of
acid (to 1 ppm), inorganic chlorides
(to 0.1 ppm), or inorganic fluorides
(to 0.1 ppm). The gaseous refrigerant,
in all but two samples was of higher
purity than the specification for new
CFC-12.
The amount of residue measured in
the CFC-12 was simply the com-
pressor oil which was carried over
into the sampling container by the
refrigerant The amount of residue in
each sample depended on the
amount of refrigerant in the air condi-
tioner, the rate at which the sample
was removed (the sampling rate), and
on how soon after the air conditioner
was used the sample was taken.
The residue (compressor oil) was
also tested for purity. It was found to
be very pure (>99% in all but one or
two samples). That impurity was
found to consist of very small
amounts (< 1 ppm) of a large number
of different organic compounds.
There was no statistically significant
correlation between residue purity
and car mileage, whether the car's
compressor was functioning, or with
the area of the U.S. where the sample
was taken.
Traces of water were found In the
refrigerant The mean for all of the
samples was found to be 56 ppm. No
statistical correlation was found
between the water content of the
refrigerant and whether the com-
pressor was working or failed nor
with the area where the sample was
taken; however, a statistically signif-
icant correlation was found between
the odometer reading of the car and
the water content The mean water
content for odometers registering up
to 18,000 mi (29,000 km) was 34 ppm.
At higher mileage ranges, the mean
moisture content of the refrigerant
was In the 56- to 94-ppm range.
This Project Summary was {level-
oped by EPA's Air and Energy
Engineering Research Laboratory, Re-
search Triangle Park, NC, 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
Approximately 25% of all domestically
consumed chlorofluorocarbons (CFC or
CFCs) are currently used in automobile
air conditioners, the single largest use of
these chemicals. Moreover, current
servicing practices result in substantial
but unnecessary emissions of CFC-12
(dichlorodifluoromethane). During typical
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servicing, any CFC-12 remaining in the
automobile air conditioner is first vented
to the air, a new charge of CFC-12 is
sometimes used to test the system and
locate the leak, and finally the system is
recharged with CFC-12 after repair. The
release of CFC to the atmosphere could
be reduced by requiring the recovery and
reuse of the refrigerant from all
automobile air conditioners serviced;
however, there has been little information
available on the level of contamination in
operating automobile air conditioners and
the ability of equipment to satisfactorily
i clean the CFC for reuse.
This project to evaluate CFC refrigerant
from automobile air conditioners was
initiated in response to these questions.
The quality of refrigerant present in
vehicles of different makes, ages, and
mileages and from different parts of the
country has now been assessed. The
refrigerant from 227 vehicles with both
failed and properly working air
conditioners was collected and tested.
The results of the program have provided
an understanding of not only the quality
of the refrigerant found in automobiles
but also of how failure of the
compressors and other equipment affects
its contamination.
The work was guided by and
performed in cooperation with an ad hoc
industry group comprised of represent-
atives of interested parties. The ad hoc
industry group agreed that the following
parameters would fully describe possible
refrigerant contaminants: water content,
acidity, residue, chloride ion, purity of the
liquid phase, purity of the gas phase
The group also determined that the
recycled refrigerant would be considered
satisfactory for reuse if recycling
equipment could achieve a standard of
purity comparable to that of the
refrigerant in properly working air
conditioners in automobiles that have
been driven for 15,000 ± 3,000 miles
(25,000 ± 5,000 km). Thus, the two main
aims of the program were: (1) to
determine the purity of CFC using the six
parameters listed above for properly
working air conditioners in cars at 15,000
± 3,000 miles, and (2) to determine the
maximum CFC contamination for cars
that will seek service due to major
component failure.
In response to the objectives,
refrigerant in 227 vehicles from different
parts of the U.S. with a variety of
mileages and automobile air conditioners
was evaluated.
Sampling Procedure
The equipment used for sampling the
automobile air conditioners consisted of a
sampling cylinder, sampling line, and a
manifold gauge set and vacuum pump
(furnished by the shop at the sampling
site).
Three hundred sampling containers
that were manufactured specifically for
this purpose were used for this program.
Each container is an (approximately) 1-
gal. (3.8 L) steel vessel equipped with a
2-way valve suitable for CFC-12. One
sampling line was made for each
container and packed with it. Before
being shipped to the sampling sites, all
sampling containers and sampling lines
were cleaned, dried and tested to ensure
that they were clean and capable of
holding pressure.
At the sampling site, the sampling
containers were filled with refrigerant
from the automobiles by placing the
sampling container into a pan of dry ice
and evacuating the line and container.
The sample was then drawn from the air
conditioning system at the high pressure
side so that lubricant would be withdrawn
with the refrigerant. Once the sampling
was completed, the air conditioning
system was serviced, if needed, and then
recharged by service center personnel
following normal procedures. For each
vehicle, the model, year, type of engine
and air conditioner, and other information
were recorded on a Vehicle Information
Form prepared for the purpose.
Analytical Procedures
The contents of each sample container
were analyzed as received by the
method indicated for the following:
1. Moisture content: Karl Fischer
titration
2. Acidity or acid number: KOH titration
3. High boiling residue or oil content:
Gravimetric analysis
4. Cleanliness or purity of the
refrigerant: GC/FID.
5. Purity of the residue: GC/FID.
6. Free halides: Ion chromatography
Results
This sampling and analytical program
showed that the refrigerant in operating
air conditioners is very pure. Acids do not
accumulate in the refrigerant. Any
impurities that accumulate in the air con-
ditioning system are concentrated in the
compressor oil. They are dissolved by
the liquid phase of the refrigerant but d
not get carried over into the gas phase
The gas phase proved to be free <
contaminants and equivalent in purity 1
new CFC-12.
Water content was the only parametc
which was highly dependent on vehicl
mileage. In more than 95% of th
samples analyzed, moisture was presei
at above the specification for new CFC
12. Table 1 summarizes the results fc
water as well as for residue purity. Th
water content of the refrigerant tended t
be greater in vehicles with highe
mileage. However, even refrigerant i
new vehicles had a moisture level greate
than the 10-ppm specification on nei
CFC-12. This may be due to the sma
amount of moisture that is present on a
manufactured parts (e.g., as th
compressor, expansion valve, and hose;
and to the migration of moisture throug
hose material. As illustrated by th
relatively small standard deviation
shown in Table 1, the moisture in th
lower mileage ranges does not vary a
much as it does in the higher mileag
ranges. The moisture level in th
refrigerant did not show any correlatio
with geographic location or vehicle make
The mean for all of the samples wa
found to be 56 ppm. No correlation wa
found between the water content of th
refrigerant and the area of the U.S. wher
the sample was taken; however,
correlation was found between th
odometer reading of the car and th
water content. The mean water conter
for cars up to 18,000 mi (29,000 km) wa
34 ppm. Above this mileage, the mea
moisture content of the refrigerant i
different mileage ranges remained in th
56- to 94-ppm range.
Contamination of the CFC-12 wit
HCFC-22 is not widespread. Only tw
cars out of more than 200 teste
contained more than the limit for ne<
CFC-12 of 0.5%. Even if it occurs, il
effect is limited since it quickly leaks 01
of the system through the hoses and ha
a very limited effect on the ai
conditioner's performance.
Neither the refrigerant nor the residu
(compressor oil) which came with
during the sampling showed an
measurable level of acid (to 1 ppm
inorganic chlorides (to 0.1 ppm), c
inorganic fluorides (to 0.1 ppm). Th
refrigerant in all the samples was bett<
than the purity requirement for new CFC
12 by these criteria.
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Table 1, Summary of Results (ppm)
Good Compressors
(miles)*
•t mi = 1.6km
Standard deviation
Moisture
Residue Purity
No.
Maximum
Mean
SO"
No.
Maximum
Mean
SD»
0-12,000
12,000-18,000
18,000-40,000
40,000-60,000
60,000-90,000
> 90,000
15
49
39
25
41
23
207
127
1,002
413
224
755
34
34
73
56
49
94
50
28
189
77
36
147
16
47
39
23
41
22
7,600
9,900
10,600
6,600
9,700
4,700
1,841
1,969
1,656
1,246
1,230
785
2,300
2,353
2,327
1,558
2,277
1,232
Subtotal
Failed Compressors
Total
Blanks
192
24
216
21
188
515 58 100 26 5,700
214
65 15 16 20 2,100
852 1.208
313 504
One possible explanation of the
absence of acid is that an automobile air
conditioner is a relatively benign environ-
ment for a material as chemically stable
as CFC-12. A second'explanation is that
the acids that might form are fully
contained in the lubricant or are
neutralized by the metal content of the air
conditioner components. There was
evidence that free acid reacted with the
material of the sampling system. This
chemical reaction would result in
deterioration of metal, but would not
degrade refrigerant.
The finding on the lack of acid is good
news for the program. Because the
sampling system was selected to closely
duplicate the recovery system that will be
used to recycle the refrigerant, there is
every reason to believe that no significant
quantity of acid will be removed from the
unit during recycling/servicing. Further-
more, any acid present during normal
capture and recycling of the refrigerant
can be removed by the recycling
equipment. Laboratory tests indicate that
acid can be neutralized by contact with
special metal compounds that can be
incorporated in the recycling equipment.
The acid is neutralized within a few
minutes of contact. Based on this labora-
tory analysis, acidity in recycled refriger-
ants will not be a problem if recycling
equipment is properly designed.
The level of residue in each sample
depended on the amount of refrigerant in
the air conditioner, the rate at which the
ample was removed (the sampling rate),
and on how soon after the air conditioner
was used before the sample was taken.
The residue detected in the samples is
primarily the compressor oil which was
carried over into the sampling container
by the refrigerant. No significant contam-
ination, other than oil, was found in the
CFC.
The residue (compressor oil) was also
tested for purity. The results are sum-
marized in Table 1. It was found to be
very pure (>99% in all but one or two
samples). The impurity was found to
consist of very small amounts (< 1 ppm)
of a large number of different organic
compounds. The concentration of any
one compound was too low to allow
identification. The residue turned out to
be a reasonably good quality compressor
oil. Attempts were made to correlate the
residue purity with car mileage, with
whether the compressor had failed or not,
and with the part of the country where the
sample was taken. No correlation was
found with any of these three parameters.
The purity of the refrigerant itself was
tested by withdrawing a sample of the
gas phase from the sampling container
and analyzing it with a gas chromato-
graph/flame ionization detector. The pur-
pose of this test was to determine
whether any of the refrigerant samples
had been contaminated with other CFCs
such as HCFC-22. The test could also
identify any gaseous products of
decomposition of the refrigerant or of the
compressor oil. Except for two samples
that showed some HCFC-22, no measur-
able extraneous materials were found in
the gas phase of the refrigerant.
Trace quantities of other CFCs and
HCFCs are common contaminants in
CFC-12 and are allowed by the speci-
fications for new CFC-12 to compose up
to 0.5% of the product. Samples of new
CFC-12 from several suppliers were
analyzed as part of this program and
were found to contain up to 0.1% HCFC-
22 as well as of other volatile compo-
nents. HCFC-22 contamination in opera-
ting automobile air conditioners cannot
remain very high because it quickly leaks
out through the rubber hose materials.
Only two samples of refrigerant out of
the 227 automobiles tested were found to
contain more than 0.5% HCFC-22 in the
CFC-12; one contained 2% and the
second 5% HCFC-22. In neither case did
the level of contamination make that air
conditioner's performance deteriorate to
the point where the owner chose to have
it repaired.
Conclusion
This sampling and analytical program
showed that the refrigerant in operating
air conditioners is very pure. Acids do not
accumulate in the refrigerant. Any
impurities that accumulate in the air
conditioning system are concentrated in
the compressor oil. They are dissolved
by the liquid phase of the refrigerant but
do not get carried over into the gas
phase. The gas phase proved to be free
of contaminants and equivalent in purity
(as measured by a gas chromatograph
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with a flame ionization detector) to new
CFC-12. The moisture level in the
refrigerant did not show any correlation
with geographic location or vehicle make.
The finding on the lack of acid is good
news for the program. Because the
sampling system was selected to closely
duplicate the recovery system that will be
used to recycle the refrigerant, there is
every reason to believe that no significant
quantity of acid will be removed from the
unit during recycling/servicing. Further-
more, any acid present during normal
capture and recycling of the refrigerant
can be removed by the recycling
equipment. Laboratory tests indicate that
acid can be neutralized by contact with
special metal compounds that can be in-
corporated in the recycling equipment.
The acid is neutralized within a few
minutes of contact. Based on this
laboratory analysis, acidity in recycled
refrigerants will not be a problem if re-
cycling equipment is properly designed.
The lack of chloride or fluoride ions in
the samples further reinforces the above
conclusion. These ions would typically
form by hydrolysis of the CFC-12, form-
ing hydrochloric or hydrofluoric acid. The
lack of these ions, coupled with the high
purity seen in the CFC-12 itself, indicates
that refrigerant breakdown does not occur
under the conditions encountered in an
automobile air conditioner.
In summary, the data gathered he
indicate that the CFC-12 refrigerant do
not degrade significantly with us
Furthermore, while small amounts of cc
taminant are removed with the refrigers
during servicing, the bulk of tl
contaminants remain with the compress
oil. Current servicing practices do r
require that the compressor oil I
changed unless the compressor is i
placed. The presence of HCFC-22
concentrations above the specification 1
new CFC-12 is rare, less than 1% of t
cars tested. HCFC-22 contaminant quic
ly leaks out of the automotive air com
tioner through hoses and, does n
appear to cause operational probler
while in the system.
L Weitzman is with Acurex Corp., Research Triangle Park, NC 27709.
Dale L Harmon is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of Refrigerant from Mobile Air
Conditioners," (Order No. PB 89-169 8821 AS; Cost: $15.95, 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:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
"V\ ecutitv i Jl'.S P!j.\i/..Ji: !•
Official Business
Penalty for Private Use $300
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EPA/600/S2-89/009
0000329 PS
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