Evaluation of the Potential Impact 

of Emissions of HFC-134a 

From Non Professional Servicing 

of Motor Vehicle Air Conditioning Systems 

CARB Agreement No. 06-341 

Prepared for 

State of California Air Resources Board 

Research Division 

PO Box 2815 

Sacramento, CA 95812

Final Report 

Arnaud TREMOULET, Youssef RIACHI, David SOUSA, Lionel PALANDRE, Denis CLODIC 

and the participation of 

Aline GARNIER for documentation 

Simon CLODIC and Martin LANSARD for surveys in California 

December 2008 
DISCLAIMER 

The statements and conclusions in this Report are those of the CEP-Armines and not 

necessarily those of the California Air Resources Board (ARB). The mention of commercial 

products, their source, or their use in connection with material reported herein is not to be 

construed as actual or implied endorsement of such products. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008

Contents 

Abstract..........................................................................................................................................................1

Executive summary .......................................................................................................................................2

Introduction....................................................................................................................................................5

1. Measurements of initial leak flow rate (LFR) of the five most used MAC systems in California ...............5

1.1 Test method ........................................................................................................................................5

1.2 Tests results........................................................................................................................................6

1.2.1 MAC system A .............................................................................................................................6

1.2.2 MAC system B ...........................................................................................................................10

1.2.3 MAC system C...........................................................................................................................12

1.2.4 MAC system D...........................................................................................................................14

1.2.5 MAC system E ...........................................................................................................................16

1.3 Conclusion.........................................................................................................................................18

Appendix 1: Leak flow rate and mole number graph MAC system A..........................................................20

Appendix 2: Leak flow rate and mole number graph MAC system B..........................................................21

Appendix 3: Leak flow rate and mole number graph MAC system C..........................................................22

Appendix 4: Leak flow rate and mole number graph MAC system D..........................................................23

Appendix 5: Leak flow rate and mole number graph MAC system E..........................................................24

2. Analysis of current recharge by non professionals in California .............................................................25

2.1 Introduction........................................................................................................................................25

2.2 Small cans: description and leak test results....................................................................................25

2.2.1 Small can description.................................................................................................................25

2.3 Analysis of recharge by do-it-yourselfers (DIYers)................................................................................26

2.3.1 Operating procedure for emission assessment .............................................................................27

2.3.2 Descriptions of the small can user sample ....................................................................................27

2.3.3 Vehicle analysis .............................................................................................................................29

2.3.4 Charging procedure evaluation......................................................................................................30

2.3.5 Refrigerant emissions associated with the use of small cans........................................................36

3. Analysis of current leak search and recharge by professional servicing in California ............................40

3.1 Introduction........................................................................................................................................40

3.2 Operating procedure to perform professional servicing analysis......................................................41

3.2.1 Simulation of AC failure .............................................................................................................41

3.2.2 Description of the MACS used..................................................................................................41

3.2.3 Selection of professional garages and sample description ......................................................43

3.3 Analysis of current leak search and recharge by professional servicing ..........................................44

3.3.1 Preliminary AC check by professional servicing......................................................................44

3.3.2 Leak search and recharge by professional servicing ..............................................................45

4. Laboratory Testing...................................................................................................................................52

4.1 Evaluation of potential leak sources of professional servicing..........................................................52

4.1.1 System performances related to refrigerant charge ..................................................................52

4.1.2 Potential leak sources during a typical maintenance procedure ...............................................54

4.1.3 Recommended service procedure.............................................................................................57

4.2 Leak tightness tests of brand new and after use small cans ............................................................58

4.2.1 Introduction ................................................................................................................................58

4.2.2 Description of small cans...........................................................................................................58

4.2.3 Tests and results........................................................................................................................63

4.2.4 Conclusions ..............................................................................................................................66

4.3 Sensitivity of different leak search methods......................................................................................67

4.3.1 Introduction ................................................................................................................................67

4.3.2 Test procedure...........................................................................................................................67

4.3.3 Leak test results and conclusions..............................................................................................68

5. Evaluation of the sales of HFC-134a disposable cans in California .......................................................71

6. Summary, conclusions, and recommendations.......................................................................................72

References ..................................................................................................................................................77

Abbreviations and acronyms .......................................................................................................................77

Annexes 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 1 -

Abstract 

This project included laboratory testing and field studies to evaluate the methods and 

procedures used by both professionals and non-professionals while servicing mobile airconditioning (MAC) systems. A majority of professional technicians used recovery and recharge 

machines with some using small cans. All non-professional do-it-yourself (DIY) individuals used 

small cans. Field testing was also conducted to determine refrigerant emissions from nonprofessional servicing. While the data indicated that the majority of the refrigerant was charged 

into the MAC systems, thirty-three percent was emitted to the atmosphere. Laboratory testing 

was performed to measure the leak rate from small cans and charging hoses and to compare 

different leak detection techniques used by professional technicians. In addition, testing was 

conducted to measure the initial leak flow rate of new MAC systems installed in the 5 most 

popular vehicles in California. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 2 -

Executive summary 

Background 

This research project will assist ARB in the mitigation of Climate Change as required in the 

California Global Warming Solutions Act. Specifically, the results of this study will assist in the 

development of a regulatory measure reducing the emissions of high global warming potential 

(GWP) refrigerants used by non-professional individuals in re-charging their motor vehicles’ air 

conditioning (MVAC) systems. ARB is interested in gaining an understanding of the nature of 

non-professional MVAC servicing and the resulting emissions of high-GWP refrigerant. In 

addition, ARB wants to evaluate professional servicing of MVAC systems in order to understand 

its advantages in comparison to non-professional servicing. The data and information from this 

project could be beneficial for the development other potential measures concerning high-GWP 

refrigerants used in MVAC systems, emission reductions from leaking MVACs, and professional 

servicing. 

Method 

This research project consisted of two parts. In one part, ARMINES’ Center for Energy and 

Processes (CEP) staff conducted field testing and field evaluations of non-professional DIY 

MVAC servicing and a field survey and evaluation of professional MVAC servicing. The rest of 

the project included the laboratory testing of different MAC systems, DIY containers and 

charging hoses, and different leak detection techniques used by professional technicians. 

The field testing included the measurement of the refrigerant emissions from non-professionals 

performing MAC servicing using “small cans.” Refrigerant emissions were determined by taking 

a mass balance approach where an individual performed a “small can” re-charge on a MVAC 

system containing a known quantity of refrigerant. This is followed by weighing the container to 

determine the remaining refrigerant and refrigerant recovery from the MVAC system in order to 

determine how much refrigerant was charged into the system by the non-professional. In 

addition, the individuals performing the DIY practice were profiled and the procedures used 

during the MVAC re-charging were characterized and evaluated. This latter qualitative approach 

was also used with professional technicians who were asked to diagnose and perform corrective 

actions on an undercharged MAC system provided in a CEP vehicle. The professionals’ 

diagnoses and servicing recommendations were compiled and evaluated. 

The laboratory testing was conducted at the CEP facility and included the measurement of the 

performance of a single MVAC system which was mounted on a test bench. During the test, 

system parameters, including evaporator air temperature, were measured to observe how the 

cooling performance decreased as the refrigerant charge was reduced. 

CEP staff also measured the leak rates of automotive refrigerant containers and the hose 

assemblies before and after container valve actuation. The containers and container/hose 

assemblies were placed inside an accumulation volume and an infrared spectrophotometer was 

used to measure the rise in refrigerant concentration inside the volume over time. Testing was 

also conducted to compare the sensitivity of different leak search methods using a leak detector, 

ultraviolet dye with a lamp, and soap/water solution on a pressurized MVAC system joints. In 

addition, CEP staff measured the annual leak flow rates (LFRs) of the MAC systems on the five 

most sold cars in California in a laboratory. The laboratory testing was performed in mini-sheds 

(small chambers) at the CEP facility. All of these leak tests were performed using a 

methodology specified in the European Regulation 706/2007. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 3 -

Results 

Non-professional Servicing 

In general, it was observed that DIY individuals recharge their MVAC systems without knowing 

the amount of refrigerant remaining in the MVAC system, the manufacturers’ specified 

refrigerant charge, and without making a diagnosis of any problems including a search for leaks. 

Moreover, instructions on the container’s label give incorrect information about re-charging the 

air conditioning system. Results from the field testing of the non-professionals indicate that twothirds of the refrigerant in the small can is charged into the MAC system with the remainder 

released to the atmosphere. Refrigerant emissions from the DIY procedure is split with two 

thirds remaining in the container (can heel) which is eventually breached releasing the contents 

to the atmosphere. One third is released to the atmosphere during recharging. Based on a field 

survey, the typical cost of a can plus the recharging kit varies from $15 to $ 40. 

Professional Servicing 

One of the benefits of professionals servicing is the diagnosis of problems with MVAC operation 

along with the servicing or repair. Most professional technicians measure the air temperature 

coming from the vents in the cabin, check the compressor clutch actuation, and measure the 

high and low pressures of the system. The vast majority of the technicians recommend the use 

of ultraviolet-sensitive dye with a UV lamp to detect leaks. Some use electronic detectors. All of 

these methods have detection limits below which these methods will not work. The majority of 

professional repair and servicing facilities use automated recovery and recharge machines 

which minimize refrigerant emissions during servicing. The cost of professional servicing ranges 

from $80 to $200 for diagnosis, recovery and recharge with a machine, and, depending on the 

shop, includes a leak search. This estimate does not include the more costly repairs such as 

replacing a compressor. 

Laboratory Testing 

Testing in the lab allowed CEP staff to collect data for MVAC systems and components under 

situations that we would not have been possible in the field. The results of the collection of 

MVAC performance data versus decreasing refrigerant charge indicated that there is no 

significant deterioration in the cooling performance until the refrigerant was reduced to 

approximately half of manufacturer’s specified charge. 

Testing was also conducted to compare three leak detection methods which included the use of 

an electronic leak detector, the detection of soap bubbles on a MVAC system pressurized with 

CO2 or air, and the injection of UV-sensitive dye into a system with the use of a UV lamp to 

detect leaks. Data from the testing indicates that the usage of UV dye is capable of detecting a 

leak of 6 g/yr with an 11 hour waiting period. This is as sensitive as an electronic leak detector 

and more sensitive than the soap bubble detection method. 

For the leak rate measurement of small containers, there is no significant emission difference 

between the screw-and-perforate (S&P) and valve-equipped cans prior to usage. However, 

when considering a used container the leak rates for the "push-button" type charging kits on the 

S&P containers were very significant when compared to the valve-equipped cans or the S&P 

containers with the shut-off valve installed. 

The average annual LFR of the five most sold MAC systems in California is 

10±4 grams per year which indicates that U.S. MVAC systems are comparable to the European 

and Japanese systems in terms of leakage. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 4 -

Conclusions 

There are significant differences between professional and non-professional servicing 

operations. The use of small cans by non-professionals results in emissions of about 1/3 of the 

refrigerant contained in small cans. It is possible that “small can” usage by professionals may 

result in lower emissions. The most significant advantage of professional servicing, in terms of 

emissions, is the use of an automated R&R machine which results in re-charging emissions that 

may be lower than 5 g per operation. This compares favorably to refrigerant emissions of more 

than 110 g per servicing when non-professionals use small cans. 

The initial leak tightness of U.S.-made MAC systems is in the neighborhood of 10 grams per 

year. If this leak tightness were to be maintained over a lifetime, no recharge should be 

necessary for 15 years. However, HFC-134a sales indicate that the leak flow rates of MAC 

systems increase with time with many MVACs requiring service after 6 to 8 years of operation. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 5 -

Introduction 

The main objective of this research project was to develop experimental data in order to better 

estimate emissions of HFC-134a due to non-professional servicing of MAC systems. The 

overall study design was divided into six tasks and are presented as follows: 

 Measurements of initial leak flow rate (LFR) of the five most used MAC systems in 

California 

 Analysis of current recharge by non-professionals in California 

 Analysis of current leak search and recharge by professional servicing in California 

 Laboratory tests simulating non-professional operating modes in California 

 Evaluation of the sales of HFC-134a disposable cans in California 

 Recovery of samples of disposable cans after usage by non-professionals in California 

1. Measurements of initial leak flow rate (LFR) of the five most used MAC systems 

in California 

1.1 Test method 

The test bench dedicated to the leak flow rate measurement of the whole AC system has been 

developed by CEP [ACE05]. The leak measurements are performed in accordance with the 

European directive 2006/40/EG [EUD06]. The test procedure detailed by the European 

regulation 706/2007 [EUR07] is described below. 

The MAC system (see Photo 1.1) is first mounted, evacuated and charged with the nominal 

manufacturer refrigerant charge (±1 gram) and then installed inside the mini-shed. 

According to the specifications given by EUR07, the pre-conditioning is performed at 50°C for 10 

days. Thereafter, the mini-shed is rinsed and tests are carried out at 40°C. In order to establish 

a regression correlation on the five U.S. MAC systems, three temperatures are successively 

controlled in order to measure the three corresponding leak flow rates (LFR). 

Photo 1.1: Installation of MAC system in mini-shed.
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 6 -

An infrared photo-acoustic spectroscope, having a detection limit of 15 ppb, measures the 

refrigerant accumulated inside the mini-shed. The mass flow rate is the product of the molar 

mass and the derivative of the number of moles of HFC-134a with respect to time in the test 

chamber volume (the test chamber). The perfect gas law is used to take into account the small 

variations of pressure and temperature inside the test chamber. According to Equation (1.2), the 

following parameters need to be determined for leak flow rate calculation: the accumulation 

volume of the test chamberVaccum , the temperature Tamb and the pressure Pamb inside the test 

chamber, and the evolution of concentration with time. 

The method used to determine the leak flow rate (LFR) is based on Equation (1.1). 

t

n

m M HFC a

HFC a HFC a

∂

∂

= ⋅

−

− −

134

134 134 & Equation(1.1)

Where, 

C

R T

P V

n n C

amb

amb accum

HFC a total ⋅

⋅

⋅

−134 = ⋅ = Equation(1.2)

HFC-134a mass flow rate (g.s-1) 

HFC-134a molar mass (102 g.mol-1) 

Number of mole (mol) 

t Time (s) 

C Refrigerant concentration (ppm) 

Ambient pressure (Pa) 

Accumulation volume (m3

) 

Gas constant (8.314x103 kJ kmol-1 K

-1) 

Ambient temperature (K) 

1.2 Tests results 

All five MAC systems were purchased from each manufacturer and mounted in the CEP test 

chambers according to manufacturers specifications and instructions. 

1.2.1 MAC system A 

System specifications 

Table 1.1 System specifications. 

Reference System A 

Type SUV 

Motorization / 

Vintage 2002-2004 

MAC system Dual evaporator 

Nominal refrigerant charge 1400 g 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 7 -

System design 

Photo 1.2 Assembled MAC system A. 

Table 1.2: List of components. 

Components Numbers of 

components Comments 

Compressor 1 

Condenser 1 

LP receiver 1 Located on the outlet of the evaporator 1 

Evaporator 2 

Expansion valve 2 Evaporator 1: Orifice tube 

Evaporator 2: TxV 

Liquid line 3 

Suction line 2 

HP service valve 1 Located on the discharge line 

LP service valve 2 Located on the liquid line 1 & 2

HP sensor 1 Located on the discharge line 

LP sensor 1 Located on the LP receiver 

Condenser

Condenser

Compressor 

Evaporator 1 

E

v

LP receiver

Services valves 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 8 -

Leak flow rate calculation 

Table 1.3 summarizes the MAC system A leak flow rates for 3 different temperatures. 

Figure 1.1 illustrates the leak flow rate as a function of pressure. 

Table 1.3: LFRs of MAC system A. 

T(°C) Saturation 

Pressure (kPa) LFR (g/yr) 

30 770 13.0 ± 0.8 

40 1017 25.3 ± 1.5 

50 13118 44.8 ± 2.7 

0

10

20

30

40

50

60

0 200 400 600 800 1000 1200 1400 1600

LFR(g/yr)

Pressure(kPa)

MAC system A

 Figure 1.1 LFRs & Regression curve. 

Using the method of least squares, a good relationship between the measured values and the 

regression curve of the binomial expression has been verified and is expressed by Equation 1.3. 

( )

2 2 Pupstream Pdownstream LFR = k − Equation(1.3)

The objective of this approximation is to find a general approach for MAC system leakage 

behavior as a function of pressure, which will be used for leak flow rate prediction at a required 

temperature. Once the equation parameter K is determined, the MAC leak flow rate is then 

calculated at the corresponding temperature for each zone. 

Considering the population for 10 California zones, the LFR is determined as a function of the 

temperature for the saturation pressure and then related to the population. 

Example: taking the Arcata zone (see Table 5), a mean temperature of 10.4°C corresponds to 

the saturation pressure of 420 kPa. Using Equation 1.3, a leak flow rate value of 4.2 g/yr 

(2.536x10-5 *(4202

-1012)) is obtained. 

 

Table 1.4 Determination of the annual LFR of MAC system A taking into account CA population. 

Arcata

Bakersf

ield Daggett Fresno

Long 

Beach

Los 

Angeles Sacramento

San 

Diego

San 

Francisco

Santa 

Maria

Annual mean T(°C) 10.4 18.5 19.8 17.1 17.2 16.7 15.2 17.6 13 .1 12.9

Saturation Pressure(kPa) 420 546 568 522 523 516 492 530 459 456

LFR(g/yr) 4.2 7.3 7.9 6.7 6.7 6.5 5.9 6.9 5.1 5.0

Population 790525 4669274 2962948 12901515 3443421 2933929 5966569 2173073 35841254

% Population 2.2% 13.0% 8.3% 36.0% 9.6% 8.2% 16.6% 6.1% 100%

LFR% 0.1 1.0 0.5 2.3 0.6 0.6 0.8 0.3 6.3

K= 2.536E-05

Total
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 9 -

Figure 1.2 LFR variations taking the population into consideration. 

Figure 1.2 shows the annual leak flow rate corresponding to the zone temperature as well as the 

annual leak flow rate related to the population. 

Evaporator 2 MAC System A 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 10 -

1.2.2 MAC system B 

System specifications 

Table 1.5 System specifications. 

Brand MAC system B 

Type Van 

Motorization 3.3 l SMPI 

Vintage 2005 

MAC system Dual evaporator 

Nominal refrigerant charge 1080 g 

System design 

Photo 1.3 Assembled MAC system B. 

Table 1.6 List of components. 

Components Numbers of 

components Comments 

Compressor 1 

Condenser 1 

HP liquid receiver 1 Located on the principal liquid line 

Evaporator 2 

Expansion valve 2 Thermal expansion valve 

Liquid line 5 

Suction line 4 

HP service valve 1 Located on the main liquid line 

LP service valve 1 Located on the main suction line

HP sensor 1 Located on the main liquid line after the HP receiver 

Evaporator 1 

Evaporator 2 

Condenser 

Compressor
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 11 -

Leak flow rate calculation 

Table 1.7 LFRs of MAC system B. 

T (°C) Saturation 

Pressure (kPa) LFR (g/yr) 

30 770 19.6 ± 1.2 

40 1017 33.0 ± 2.0 

50 13118 59.4 ± 3.6 

0

10

20

30

40

50

60

70

0 200 400 600 800 1000 1200 1400 1600

LFR(g/yr)

Pressure(kPa)

MAC system B

 Figure 1.3 LFRs & Regression curve of MAC system B. 

Table 1.8 Determination of the annual LFR of MAC system B taking into account CA population. 

Arcata

Bakersf

ield Daggett Fresno

Long 

Beach

Los 

Angeles

Sacrame

nto

San 

Diego

San 

Francisc

o

Santa 

Maria

Annual mean T(°C) 10.4 18.5 19.8 17.1 17.2 16.7 15.2 17.6 13 .1 12.9

Saturation Pressure(kPa) 420 546 568 522 523 516 492 530 459 456

LFR(g/yr) 5.6 9.7 10.6 8.9 8.9 8.7 7.8 9.2 6.8 6.7

Population 790525 4669274 2962948 12901515 3443421 2933929 5966569 2173073 35841254

% Population 2.2% 13.0% 8.3% 36.0% 9.6% 8.2% 16.6% 6.1% 100%

LFR% 0.1 1.4 0.7 3.1 0.8 0.7 1.1 0.4 8.4

K= 3.382E-05

Total

Figure 1.4 LFR variations taking the population into consideration. 

MAC System B
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 12 -

1.2.3 MAC system C

System specifications 

Table 1.9 System specifications. 

Brand MAC system C 

Type Pickup 

Motorization 5.4 l 

Vintage 2007 

MAC system Single evaporator 

Nominal refrigerant charge 940 g 

System design 

Photo 1.4 Assembled MAC system C. 

Table 1.10 List of components. 

Components Numbers of 

components Comments 

Compressor 1 

Condenser 1 

Evaporator 1 

LP receiver 1 

Expansion valve 1 Orifice tube 

Discharge line 1 

Liquid line 1 

Suction line 2 

HP service valve 1 Located on the discharge line 

LP service valve 1 Located on the suction line 

HP sensor 1 Located on the suction line 

LP sensor 1 Located on the LP receiver 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 13 -

Leak flow rate calculation 

Table 1.11 LFRs of MAC system C. 

T (°C) Saturation 

 Pressure (kPa) LFR (g/yr) 

30 770 13.9 ± 0.8 

40 1017 21.7 ± 1.3 

50 13118 35.4 ± 2.1 

0

5

10

15

20

25

30

35

40

45

0 200 400 600 800 1000 1200 1400 1600

LFR(g/yr)

Pressure(kPa)

MAC system C

 Figure 1.5 LFRs & Regression curve of MAC system C. 

Table 1.12 Determination of the annual LFR of MAC system C taking into account CA population. 

Arcata

Bakersf

ield Daggett Fresno

Long 

Beach

Los 

Angeles Sacramento

San 

Diego

San 

Francisco

Santa 

Maria

Annual mean T(°C) 10.4 18.5 19.8 17.1 17.2 16.7 15.2 17.6 13 .1 12.9

Saturation Pressure(kPa) 420 546 568 522 523 516 492 530 459 456

LFR(g/yr) 3.5 6.0 6.5 5.5 5.5 5.4 4.9 5.7 4.2 4.1

Population 790525 4669274 2962948 12901515 3443421 2933929 5966569 2173073 35841254

% Population 2.2% 13.0% 8.3% 36.0% 9.6% 8.2% 16.6% 6.1% 100%

LFR% 0.1 0.9 0.5 1.9 0.5 0.5 0.7 0.3 5.2

K= 2.093E-05

Total

Figure 1.6 LFR variations taking the population into consideration. 

MAC System C 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 14 -

1.2.4 MAC system D 

System specifications 

Table 1.13 System specifications. 

Brand MAC system D 

Type Family car 

Motorization 2.4 l 

Vintage 2006 

MAC system Single evaporator 

Nominal refrigerant charge 650 g 

System design 

Photo 1.5 Assembled MAC system D. 

Table 1.14 List of components. 

Components Numbers of 

components Comments 

Compressor 1 

Condenser 1 

Evaporator 1 

Expansion valve 1 Thermal expansion valve 

LP liquid receiver 1 

Liquid line 3 

Suction line 2 

HP service valve 1 Located on the liquid line 2 

LP service valve 1 Located on the suction line 1 

HP sensor 1 Located on the liquid line 2 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 15 -

Leak flow rate calculation 

Table 1.15 LFRs of MAC system D.

T (°C) Saturation 

 Pressure (kPa) LFR (g/yr) 

30 770 28.4 ± 1.7 

40 1017 49.1 ± 2.9 

50 13118 95.3 ± 5.7 

0

20

40

60

80

100

120

0 200 400 600 800 1000 1200 1400 1600

LFR(g/yr)

Pressure(kPa)

MAC system D

 Figure 1.7 LFRs & Regression curve of MAC system D. 

Table 1.16 Determination of the annual LFR of MAC system D taking into account CA population. 

Arcata

Bakers

field Daggett Fresno

Long 

Beach

Los 

Angeles Sacramento

San 

Diego San Francisco

Santa 

Maria

Annual mean T(°C) 10.4 18.5 19.8 17.1 17.2 16.7 15.2 17.6 13 .1 12.9

Saturation Pressure(kPa) 420 546 568 522 523 516 492 530 459 456 Total

K= 5.29E-05

LFR(g/yr) 8.8 15.2 16.5 13.9 13.9 13.6 12.3 14.3 10.6 10.5

Population 790525 4669274 2962948 12901515 3443421 3E+06 5966569 2173073 35841254

% Population 2.2% 13.0% 8.3% 36.0% 9.6% 8.2% 16.6% 6.1% 100%

LFR% 0.2 2.2 1.1 4.9 1.2 1.2 1.8 0.6 13.1

Figure 1.8 LFR variation taking the population into consideration. 

MAC System D 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 16 -

1.2.5 MAC system E 

System specifications 

Table 1.17 System specifications. 

Brand MAC system E 

Type Family car 

Motorization - 

Vintage 2006 

MAC system Single evaporator 

Nominal refrigerant charge 800 g 

System design 

Photo 1.6 Assembled MAC system E. 

Table 1.18: List of components.

Components Numbers of 

components Comments 

Compressor 1 

Condenser 1 

Evaporator 1 

Expansion valve 1 Thermal expansion valve 

Liquid line 2 

Suction line 2 

Discharge line 1 

HP service valve 1 Located on the liquid line 

LP service valve 1 Located on the suction line 

HP sensor 1 Located on the liquid line 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 17 -

Leak flow rate calculation

Table 1.19 LFRs of MAC system E. 

T (°C) Saturation 

 Pressure (kPa) LFR (g/yr) 

30 770 24.2 ± 1.5 

40 1017 45.3 ± 2.7 

50 13118 82.3 ± 4.9 

0

10

20

30

40

50

60

70

80

90

100

0 200 400 600 800 1000 1200 1400 1600

LFR(g/yr)

Pressure(kPa)

MAC system E

 Figure 1.9 LFRs & Regression curve of MAC system E. 

Table 1.20 Determination of the annual LFR of MAC system E taking into account CA population. 

Arcata

Bakersf

ield Daggett Fresno

Long 

Beach

Los 

Angeles Sacramento

San 

Diego

San 

Francisco

Santa 

Maria

Annual mean T(°C) 10.4 18.5 19.8 17.1 17.2 16.7 15.2 17.6 13 .1 12.9

Saturation Pressure(kPa) 420 546 568 522 523 516 492 530 459 456

LFR(g/yr) 7.7 13.3 14.5 12.2 12.2 11.9 10.7 12.5 9.3 9.2

Population 790525 4669274 2962948 12901515 3443421 2933929 5966569 2173073 35841254

% Population 2.2% 13.0% 8.3% 36.0% 9.6% 8.2% 16.6% 6.1% 100%

LFR% 0.2 1.9 1.0 4.3 1.0 1.0 1.5 0.6 11.5

K= 4.636E-05

Total

Figure 1.10 LFR variation taking the population into consideration. 

MAC System E
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 18 -

1.3 Conclusion 

The annual leak flow rate of a specified zone is related to its saturation temperature and 

saturation pressure as well as to the population. It is remarkable that the annual leak flow rate is 

more dependent on the population than temperature (see Figures 1.11 and 1.12). With 36% of 

California’s population, the annual LFR in Los Angeles represents 37% of California’s LFR, even 

though its average annual temperature is 16°C. 

Figure 1.11 Population distribution. Figure 1.12 Annual LFR distribution as a function of 

population and temperature zones. 

System K LFR@Temp

A 2.536E-05 6.3 

B 3.382E-05 8.4 

C 2.093E-05 5.2 

D 5.295E-05 13.1 

E 4.636E-05 11.5 

Figure 1.13 Vehicle annual LFR as a function of the pressure. 

Another major conclusion can be drawn: the LFRs of MAC systems mounted on the five most 

sold cars in California confirm that the automotive industry is a global one, because the LFRs 

measured are in the same range as those measured in Europe or in Japan on MAC systems of 

fleet of vehicles and in laboratories: the average annual LFR of new systems is around 10 g/yr 

±4 and possibly higher for some double evaporator systems. If this LFR were to be maintained, 

then MVACs would not need re-charging during the life of the vehicle. This is not the case due 

to the large quantities of refrigerant sold for the servicing of the systems. In addition, ARB 

performed one study (Vincent et al.) in which the data indicated that most MVAC servicing 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 19 -

occurs after 8 to 9 years of vehicle life. This study which included data from more than 12,500 

vehicles estimated that the average LFR from MVAC systems is about 80 g/yr over the lifetime 

of the vehicles. Thus, the tightness of MVAC systems degrades over time probably due to a 

variety of factors including system operation, operating temperatures, and vibrations due to 

vehicle operation. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 20 -

Appendix 1: Leak flow rate and mole number graph MAC system A 

• T=30°C 

0

100

200

300

400

500

600

0

5

10

15

20

25

30

35

40

45

50

55

60

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q (mole)

28/03/08- System A

T = 30 °C - LFR: 13.0 g/yr

LFR(g/yr)

R-134a mole number

• T=40°C 

0

100

200

300

400

500

600

700

800

900

1000

1100

0

5

10

15

20

25

30

35

40

45

50

55

60

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q (mole)

31/03/08- System A

T = 40 °C - LFR: 25.3 g/yr

LFR(g/yr)

R-134a mole number

• T=50°C 

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

0

5

10

15

20

25

30

35

40

45

50

55

60

0 2 4 6 8 10 12 14 16 18 20 22

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q (mole)

02/04/08- System A

T = 50 °C - LFR: 44.8 g/yr

LFR(g/yr)

R-134a mole number
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 21 -

Appendix 2: Leak flow rate and mole number graph MAC system B 

• T=30°C 

0

100

200

300

400

500

600

700

800

0

5

10

15

20

25

30

35

40

45

50

55

60

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

04/02/08- System B

T=30 °C - LFR: 19.6 g/yr

LFR(g/yr)

R-134a mole number

• T=40°C 

0

100

200

300

400

500

600

700

800

900

1000

0

5

10

15

20

25

30

35

40

45

50

55

60

0 2 4 6 8 10 12 14 16 18 20 22 24 26

LFR(g/yr)

Q(mole E-6)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

06/02/08- System B

T=40 °C - LFR: 33.0 g/yr

LFR(g/yr)

R-134a mole number

• T=50°C 

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

0

5

10

15

20

25

30

35

40

45

50

55

60

0 2 4 6 8 10 12 14 16 18 20

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

07/02/08- System B

T=50 °C - LFR: 59.4 g/yr

LFR(g/yr)

R-134a mole number
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 22 -

Appendix 3: Leak flow rate and mole number graph MAC system C 

• T=30°C 

0

200

400

600

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20 22 24

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

27/04/08 - MAC system C

LFR@30°C : 13.9 g/yr

LFR(g/yr)

R-134a mole number

• T=40°C 

0

200

400

600

800

1000

1200

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

28/04/08 - MAC system C

LFR@40°C : 21.7 g/yr

LFR(g/yr)

R-134a mole number

• T=50°C 

0

200

400

600

800

1000

1200

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20 22 24

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

02/05/08 - MAC system C

LFR@50°C : 35.4 g/yr

LFR(g/yr)

R-134a mole number
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 23 -

Appendix 4: Leak flow rate and mole number graph MAC system D 

• T=30°C 

0

200

400

600

800

1000

1200

1400

1600

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

23/01/08 - MAC system D

LFR@40°C : 28.4 g/yr

LFR(g/yr)

R-134a mole number

• T=40°C 

0

200

400

600

800

1000

1200

1400

1600

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

25/01/08 - MAC system D

LFR@40°C : 49,1 g/yr

LFR(g/yr)

R-134a mole number

• T=50°C 

0

500

1000

1500

2000

2500

3000

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20 22 24

Q(mole E-6)

LFR(g/yr)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

28/01/08 - MAC system D

LFR@50°C : 95.3 g/yr

LFR(g/yr)

R-134a mole number
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 - 24 -

Appendix 5: Leak flow rate and mole number graph MAC system E 

• T=30°C 

0

200

400

600

800

1000

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14 16 18 20

LFR(g/yr)

Q(mole E-6)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

14/02/08 - MAC system E

LFR@30°C : 24.2 g/yr

LFR(g/yr)

R-134a mole number

• T=40°C 

0

200

400

600

800

1000

1200

1400

1600

1800

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14 16 18 20 22 24 26

LFR(g/yr)

Q(mole E-6)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

15/02/08 - MAC system E

LFR@40°C: 45.3 g/yr

LFR(g/yr)

R-134a mole number

• T=50°C 

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14 16 18 20 22 24

LFR(g/yr)

Q(mole E-6)

Time (hr)

Leak flow rate LFR (g/yr) & mole number Q(mole)

16/02/08 - MAC system E

LFR@50°C: 82.3 g/yr

LFR(g/yr)

R-134a mole number
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -25 -

2. Analysis of current recharge by non professionals in California 

2.1 Introduction 

In order to evaluate the potential impact of HFC-134a emissions from non-professional servicing 

of MVAC systems, the ARB commissioned the CEP for a study including field tests in order to 

measure refrigerant emissions during 50 real refilling operations of MVAC systems. 

The research project aims to identify emission rates due to non-professional servicing as 

compared to professional servicing based on servicing operating modes observed in the State of 

California. 

Given enough time, a leaky MVAC system will release its entire refrigerant content to the 

atmosphere if the refrigerant leak is significant. The MVAC system leak flow rates imply one or 

more recharge(s) of the MVAC system during the vehicle’s lifetime. During a charging process, 

refrigerant emissions could be classified into two categories: 

 Direct emissions due to leaks from disposable containers (cans or cylinders), hoses, and 

fittings; or 

 Heel emissions due to the refrigerant remaining in the disposable containers after

charging. 

Section 2.2 describes the disposable small cans available on the Californian market, including 

contents, prices, and types. Leaks before and after use of some can samples have been 

measured in the laboratory and are presented in Section 4.2. 

Analysis of current recharge by non-professionals, Do-It-Yourselfers (DIYers), in California is 

presented in Section 2.3. The know-how and the expert skills have to be taken into account 

when drawing conclusions. Two sampling groups of non-professionals are considered and 

classified based on their qualifications. Analyses will be made for each sampling group as well 

as for the non-professional DIYers who have recharged different MVAC systems. 

2.2 Small cans: description and leak test results

2.2.1 Small can description 

Two categories of small cans (SC) are available on the Californian market: 

 Screwed and Perforated Cans (S&P) (Photo 2.1) 

 Cans equipped with a valve and an optional pressure gauge (V-type) (Photo 2.2) 

S&P cans are available in different capacities: 12, 13, 14, 18, and 19 oz. V-type cans are 

available in 14 oz and 19 oz capacities. 

Photo 2.1 S&P Can Photo 2.2 Can equipped with a valve 

and pressure gauge. 

Photo 2.3 Re-usable charging kit for 

S&P small cans. 

S&P cans are connected to a charging kit. Photo 2.3 presents an example of a charging kit. 

This charging kit is usually composed of: 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -26 -

 Can tap: perforating valve, with a screw fitting 

 Flexible hose 

 Service valve adaptor: low-pressure fitting 

 Pressure gauge (optional) 

Table 2.1 lists a large variety of small cans available on the Californian market, their type, 

content, market price, and online price. A list of small cans and their characteristics is presented 

in Annex A. 

Table 2.1 Small cans details. 

SC brand name Model Type Content Price 

Kragen

Price 

Kragen 2

Price Net 

www.partsamerica.com/

Quest Normal S&P 12 oz 7.99 $ 

Quest UV S&P 12 oz 11.99 $ 

Quest Stop Leak S&P 12 oz 11.99 $ 

Quest Sub Zero Polar 

Bear 

S&P + reusable 

kit 19 oz 28,99 $ 25.99 $ $24.99 

Johnsen S&P 12 oz 7,99 $ 8.99 $ $8.99 

Johnsen UV Dye S&P 12 oz 14.99 $ 

Interdynamics EZ Chill Valve equipped 14 oz 21,99 $ 17.99 $ 

Interdynamics Arctic Freeze S&P 13 oz 13.99 $ $12.99 

Interdynamics Arctic Freeze Valve equipped 

+ gauge 

12 oz 39.99 $ 

Interdynamics Arctic Freeze Valve equipped 19 oz $32.99 

Interdynamics Arctic Freeze with 

Reusable Trigger Valve equipped 14 oz $26.99 

Interdynamics EZ Chill+hose Valve equipped 28.99 $ 

Interdynamics 

EZ Chill 

Measure/Recharge 

Kit 

Valve equipped 

+ gauge 

19 oz $24.99 

Interdynamics Arctic Freeze S&P 18 oz $27.99 

To conclude, the S&P cans are cheaper than the V-type cans The S&P price varies according 

to the refrigerant content and the brand name. In order to save money people prefer to buy the 

charging kit once and then reuse it with S&P cans. It should be noted that the S&Ps are 

dominant (nearly 90% of the market, as assessed by several dealers) for two reasons: the more 

knowledgeable DIYers buy S&Ps due to the ease of use; less knowledgeable, but price-oriented 

DIYers also choose S&Ps. 

2.3 Analysis of recharge by do-it-yourselfers (DIYers) 

The aim of this section is to determine refrigerant emissions when a MVAC is charged by a 

DIYer. When charging their own car, a DIYer releases direct and indirect refrigerant emissions 

into the atmosphere. Direct emissions are those emitted during the charging process (leaks 

from the hose, can tap, and service valve adaptor). Indirect emissions, known as “heel 

emissions”, are refrigerant remaining in the can after the DIYer has disconnected the service 

valve adaptor. If the kit is leaking, sooner or later the refrigerant remaining in the can will be 

released. An operating procedure needs to be developed in order to assess the different 

refrigerant emissions and the effective refrigerant mass charged in the MVAC. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -27 -

2.3.1 Operating procedure for emission assessment 

The operating procedure used to evaluate refrigerant emissions was carried out according to the 

following method described below: 

 The CEP team performs an initial refrigerant recovery. The refrigerant charge of the MAC 

system is recovered (and weighed) in order to evaluate the efficiency of the charge operation 

made by the SCU (small can user). 

 The CEP team partially charges the AC loop (typically 1/3 of the original charge), in order to 

perform the charging process under realistic conditions: the pressure is the R-134a 

saturating pressure. 

Note: If the system is evacuated and maintained under a relative vacuum, the charge with small cans 

is not representative of the usual use.

 Before the beginning of the SCU operation, different types of small cans are displayed to the 

individual. The SCU is free to choose one, or select the type that he usually uses for 

charging the AC system. 

 The SCU proceeds in charging his AC system. He is free to use the number of small cans 

he wants. The CEP personnel take mental notes of the operation steps. After the operation 

is complete, the description is written on a dedicated field report. 

 The CEP evaluates the refrigerant emissions during the charging process as well as the can 

heels. Can heels are measured by weighing the can before charging and after charging, and 

before the de-connection from the service valve. When the can cannot be weighed because 

the SCU dismounts it right away, emissions are included in the operation. 

 The SCU is interviewed on his usual practice with small cans (periodicity of use, etc.) and 

some advice is given. 

 The CEP team recovers the refrigerant from the MAC system after the charging process and 

the effective refrigerant mass charged into the system is known by the difference. 

2.3.2 Descriptions of the small can user sample 

The number of DIYers participating in this study is 50. This includes 5 persons who have been 

interviewed, but who have not performed the charge. They have answered the questions 

describing what they usually do for charging. The other 45 persons performed the charging 

procedure, either on their own vehicles or on the CEP cars. The 50-person sample is divided 

into two sampling groups. The first one takes into account the 30 cases presented in the first 

intermediate report (October 2007). The second sampling group gathers the remaining 20 

cases done after the first report was presented. The second sampling group is comprised of 

persons who are relatively familiar with small cans. 

Conclusions are consequently drawn for the two sampling groups as well as for the overall 

sample. Conclusions are intentionally divided into three groups in order to take into account the 

effect that experience and knowledge has on the refrigerant release. 

Sample 1 This sample includes 30 persons who have been interviewed, observed doing the 

charging process (5 persons), and those who performed the charging procedure, either on their 

own vehicles or on the CEP cars (25 persons). The 25 cases include: 

 16 persons (all not SC experts), who have charged the MAC system on their own vehicles, 

 6 others persons, who have made the refrigerant charge of the CEP rental car (Chevrolet), 

and, 

 3 others who have made the refrigerant charge on a 1990 Cadillac Deville purchased by 

CEP. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -28 -

Sample 2 This sample includes 20 cases where the charging process was made on a 1999 

Mitsubishi Montero owned by CEP. The CEP team asked for help from persons near auto-parts 

stores due to the malfunctioning of the Mitsubishi MVAC system. 17 persons performed the 

operation, while 3 people told the CEP staff how to re-charge the air conditioner. The CEP team 

performs exactly what the person asks him to do. 

Small can user sample (30 cases)

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

Male Female <30 yr old >30 yr old User of SCNon user of

SC

Number of vehicles

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Smaple percentage

Small can user sample (20 cases)

0

2

4

6

8

10

12

14

16

18

20

22

Male Female <30 yr old>30 yr old Expert User of

SC

Non user

of SC

Number of vehicles

0%

20%

40%

60%

80%

100%

Sample percentage

Figure 2.1 Small can users - Sample 1. Figure 2.2 Small can users - Sample 2 

The first sample of small can users are mainly composed of males. Two saleswomen working at 

the Kragen auto-parts store helped the CEP team to fill their car while simulating a defective AC. 

23 persons are older than 30, and 5 are familiar with car self-servicing, but they are not experts 

in air conditioning (see Figure 2.1). 67% of the 30 persons declared that they had already used 

small cans on their car air conditioner. The others have never used small cans before, but they 

were interested either for curiosity or for saving money by avoiding professional service. 

For the second sample, all persons are men, among whom 12 are older than 30. 80% of the 20 

persons acknowledged the use of SC. They had made the charging procedure on their own car 

or on a family member car before or, at least, they watched someone doing it before. The 

second sample comprises a large proportion of users familiar with SCs compared to the first 

sample (see Figure 2.2). 

Small can user sample (50 cases)

0

5

10

15

20

25

30

35

40

45

50

Male Female <30 yr old >30 yr old User of SCNon user of

SC

Number of vehicles

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Sample percentage

Figure 2.3 Small can users – All 50 cases 

SC: Small Cans 

SCU: Small Can Users 

Now, considering the whole sample of 50 persons, more than 72% of the sample has used a 

small can before (see Figure 2.3). 40% are familiar with car self-servicing, meaning that they 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -29 -

know how to proceed in recharging the MVAC (nevertheless they can sometimes make wrong 

operations). 

2.3.3 Vehicle analysis 

Figure 2.4 illustrates the car vintage of the 30 cases studied in the first sample. Five vehicles 

were originally filled with R-12 (vintage 1990 and 1991), but the retrofit to R-134a had been done 

previously, and the AC loop was equipped with an R-134a fitting when the charge with the small 

can had been done. The 5 cases on retrofitted R-12 vehicles included the three refrigerant 

chargings of the CEP Cadillac. The CEP rental car (Chevrolet) has been used 8 times (2 times 

for interviews and observing people helping the CEP team, and 6 times for a charging 

procedure). The Cadillac is used three times for the charging process. 

The 20 cases in Sample 2 were performed on the 1999 Mitsubishi Montero. 

The overall number of recharging procedures made is 45, distributed as follows: 

 16 times on different vehicles owned by the DIYers, 

 6 times on the CEP rental car (Chevrolet), 

 3 times on the CEP Cadillac Deville and 

 20 times on the CEP Mitsubishi Montero. 

Car vintage of the 16 vehicles owned by the DIYers 

As shown on Figure 2.4, most 

cars were less than 10-years 

old. When looking at Figures 

2.4 and 2.5, one may wonder 

if the older car had the lower 

refrigerant charge. In fact, 

the distribution of low 

refrigerant charges remaining 

in the MAC system is not 

related to the car vintage. 

0

1

2

3

1991

199219931994

19951996

19971998

199920002001

20022003

20042005

2006

Number of Vehicles

Figure 2.4 Car vintage for the 16 vehicles owned by the DIYers. 

Initial charge/nominal charge (16 cases)

0

1

2

3

4

5

6

0% to 10%

10% to 25%

25% to 50%

50% to 75%

75% to 100%

Number of vehicles .

0%

5%

10%

15%

20%

25%

30%

35%

Sample percentage .

Period before last refrigerant refill (16 Cases)

0

1

2

3

4

5

6

7

1/2 year 1 year 2 years 3 years 4 years 10 years ND

Number of vehicles .

0%

5%

10%

15%

20%

25%

30%

35%

40%

Sample percentage .

Figure 2.5 Initial charge / nominal charge 

before the SC charging. 

Figure 2.6 Periodicity of small can use. 

ND: Not Defined
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -30 -

Figure 2.5 shows the initial charge of each vehicle, measured before the charging process with a 

small can. It indicates the number of vehicles (left scale) and the percentage on the sample 

(right scale). They are classified in categories depending on their initial refrigerant content (x 

axis). 

Two vehicles were nearly empty of refrigerant before the operation. One third of the sample had 

an initial refrigerant charge between 75% and 100% of the nominal charge. One quarter of the 

sample had their AC working with a charge between 50% to 75%. 45 % have their system either 

working very badly (25%) or not working at all (20%). Nearly 45% of the sample check their AC 

annually (see Figure 2.6). After the recovery, all AC systems have been evacuated and 

recharged with a partial charge (1/3 of the corresponding nominal charge). 

2.3.4 Charging procedure evaluation 

Choice of small can 

DIYers have to choose the small can type they want. Most of them chose the “screwed and 

perforated” type. 77% and 80% chose the S&P type respectively for Samples 1 and 2 (see 

Figures 2.7 and 2.8). The 12-oz capacity can, the smallest available, is preferred to the others, 

representing nearly 64% of the overall sample (see Figure 2.9). 

Type of small can used (30 cases)

0

2

4

6

8

10

12

14

16

18

20

22

24

26

perforated &

screw ed

valve

equipped

12oz 14 oz 18 oz 19 oz

Number of vehicles 

0%

10%

20%

30%

40%

50%

60%

70%

80%

Sample percentage

Type of small can used (20 cases)

0

2

4

6

8

10

12

14

16

18

perforated &

screw ed

valve

equipped

12oz 13 oz 14 oz 19 oz

Number of vehicles 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Sample percentage

Figure 2.7 Type and capacity of small can chosen by

the users (Sample 1). 

Figure 2.8 Type and capacity of small can chosen by

the users (Sample 2). 

Type of small can used (50 cases)

0

5

10

15

20

25

30

35

40

45

perforated

& screw ed

valve

equipped

12oz 13 oz 14 oz 18 oz 19 oz

Number of vehicles 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Sample percentage

 SC selection criteria

0

2

4

6

8

10

12

14

simpler to

use

Have

used the

same can

type

before

have

already 

the

charge kit

cheaper bigger

capacity

pressure

gauge

equipped

no

response

Number of Vehicles 

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

Sample percentage 

Figure 2.9 Type and capacity of small can chosen by the 

users (overall sample). 

Figure 2.10 Criteria for small can type choice. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -31 -

Figure 2.10 indicates criteria used by DIY individuals in selecting the type of container. The most 

frequent one is that the individual already possesses an S&P charging assembly and naturally 

selects an S&P-type container. Referred to in Table 1.1, the price of the valve-equipped can is 

two to three times higher than that of the S&P can. In addition if the SCU wants to use more 

than one can, he would prefer to buy the S&P with the reusable charging kit. 

Based on the number of persons who had already performed the procedure on their own 

vehicles, 63% of small can users decided to recharge their AC because of lack of cooling 

performance (see Figure 2.11). This fact is consistent with the analysis of the refrigerant content 

(see Figure 2.5) before servicing: two third of the sample have an initial refrigerant content lower 

than 75% of the nominal charge. Nearly half of the fleet was below a 50% refrigerant nominal 

charge. 

Refrigerant nominal charge knowledge

yes

26%

no

74%

Figure 2.11 The reasons to use a small can. Figure 2.12 Knowledge of the AC nominal charge. 

Only 26% of the small can users know the mass of refrigerant to be filled in their system (see 

Figure 2.12). Among the selection criteria announced by the DIYers, it is amazing that none of 

them relates the can capacity to the vehicle’s original charge. All criteria that DIYers take into 

account are mentioned in Figure 2.10. 

In fact, the can capacity should be an important criterion for the DIYer when choosing a SC 

because the can capacity is directly linked to the system nominal charge (announced by the 

manufacturer) and to the remaining AC system charge. A system whose nominal charge is 

900 grams needs two or more 12-oz cans. 

Indeed, the information and equipment available to DIYers are usually too limited to allow them 

to know how much refrigerant to add or when the system is fully charged. This lack of 

information can lead to the ineffective use of small cans as well as the inappropriate charging of 

the MVAC system. 

Charging procedure 

No instructions were given to small can users during their operation. They were observed and 

the facts and actions are reported on in Figures 2.13 to 2.15 respectively for the first, second, 

and overall samples. 

Sample 1 people seem to be less familiar with SCs as compared to those of Sample 2. The 

following criteria verify this observation. 

Reading instructions chart: Nearly 67% of people read the instructions in Sample 1 compared to 

35% in Sample 2. Usually they think they already know what to do and many times do not read 

the instructions any more. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -32 -

Sample 1 

Figure 2.13 Report of facts and actions during the charging process of small can users (sample 1). 

Engine on or off: several persons in Sample 1 did not turn on the engine (18%) or the AC system 

(20%) as shown in Figure 2.13. In contrast, all persons of Sample 2 did turn on the engine and 

the AC system (see Figure 2.14). 

Shaking the can: 75% of Sample 2 shook the can during charging, while only 50% did in 

Sample1. 

Sample 2 

Figure 2.14 Report of facts and actions during the charging process of small can users (Sample 2). 

Note: Nearly all SCUs when shaking the can were shaking it strongly. Some were shaking the can from 

the vertical to the horizontal position, and others were only shaking it with small amplitude (not moving it 

up to the horizontal position). In any case, the refrigerant charge is a two-phase flow. 

Nevertheless, only 75% of Sample 2 correctly performed the procedure compared to 48% for 

Sample 1. These values reflect that the familiarity with SCs is not a sufficient condition to 

charge correctly. 

Now, considering the overall sample, more than 58% proceeded correctly by turning on the 

engine and the AC, and shaking the can from horizontal to vertical positions in order to charge in 

both the liquid and vapor phases. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -33 -

Note: When the loop is equipped with a suction line accumulator, charging in liquid phase is not 

dangerous for the compressor. But if there is a HP receiver associated with a thermal expansion 

valve (TxV), it could damage the compressor (liquid slugging). 

Figure 2.15 Report of facts and actions during the charging process of small can users 

(overall sample). 

Criteria to stop charging the AC 

Criteria to stop charging with small can (50 cases)

0

5

10

15

20

25

30

Pressure

gauge 

Air

temperature

Charging

time

The can is

empty 

Bubbles on

the HP

receiver

Number of vehicles 

0%

10%

20%

30%

40%

50%

60%

Sample percentage 

Figure 2.16 Diagnostic to stop charging. 

Small can users were asked why they decided to stop charging the AC system. They could 

have answered one or two reasons (the number of answers is higher than the number of users). 

The air temperature at the AC outlet and verification by shaking the can to determine if liquid 

remained in the can were the most frequent reasons for stopping the recharge. Fifty percent 

measured the blown air temperature in the car to make sure the cooling was effective. The 

measure is subjective as they did not use any temperature sensor. Fifty percent stopped the 

charge when the can was empty. They would shake the can to see if it was empty; while others 

felt the can temperature: when the can was still cold, some refrigerant remained. 

Note: Fifty percent answered that they stopped charging when the can was empty, but this fact 

does not mean that the cans were empty at the end of the different operations. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -34 -

For cans equipped with a pressure gauge indicator, some of the people who read the 

instructions written on the cans followed the instruction that the charge is complete when the 

“Pressure ranges between 25 psi and 40 psi”. More than 35% of the answers are based on this 

criterion (see Figure 2.16). The pressure gauge indicates only the low-side system pressure 

showing different values and colors to indicate when the system is “undercharged”, “full”, or 

“overcharged” with refrigerant. But the system condition is dependent on more than just the 

amount of refrigerant in the MVAC system. The low-side pressure gauge indicates that 

refrigerant is circulating in the MVAC system and not the amount. A low-side gauge pressure of 

zero would indicate an empty system. Therefore, the kit gauge reading does not provide the 

information needed to determine the amount of refrigerant needed or the criteria to stop 

charging. On the contrary, wrong readings are delivered through the tag and the gauge. 

Number of cans used to complete the refrigerant charge 

Number of cans used during the filling process (30 cases)

0

2

4

6

8

10

12

14

16

18

20

1 can 2 cans 3 cans

Number of vehicles 

0%

10%

20%

30%

40%

50%

60% Sample percentage 

Number of cans used during the filling process (20 cases)

0

2

4

6

8

10

12

14

16

18

20

1 can 2 cans 3 cans

Number of vehicles 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Sample percentage 

Figure 2.17 Cans used during charging (Sample 1). Figure 2.18 Cans used during charging (Sample 2). 

The number of cans used during the charging process is directly related to the knowledge and 

the qualification of the user. In fact, without making a complete recovery, nobody can evaluate 

or estimate the quantity of refrigerant to be charged. Moreover, because the exact refrigerant 

mass that has been charged is also unknown, the number of cans is based on random issues. It 

may be that certain small can users are very cautious and use only a single can in order to avoid 

a major loss of refrigerant due to a significant leak or leaks. Another consideration would be 

over-charging which may damage the system. 

Obviously, in Sample 1 more 

SCUs have used more cans 

than in Sample 2. 63% have 

used 1 can compared to 95% 

in Sample 2. Two of the three 

SCUs who used three cans 

did not proceed correctly. 

Most of small can users 

choose the smaller capacity 

cans (12 oz) (see Figure 2.9). 

As shown in Figure 2.19, 

nearly 76% of operations were 

done with 1 can. 18% of 

operations were done with 2 

cans and only 6% with 3 cans. 

Number of cans used during the filling process (50 cases)

0

5

10

15

20

25

30

35

40

1 can 2 cans 3 cans

Number of vehicles 

0%

10%

20%

30%

40%

50%

60%

70%

80%

Sample percentage 

Figure 2.19 Cans used during charging (overall sample). 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -35 -

Refrigerant charging time 

Here again, a DIYer familiar with SCs will recharge the system in 5 to 10 minutes. In fact, the 

charging time depends on both the filling mode (liquid or vapor) and on the can size. The 

regular time for charging a 12-oz small can, applying the correct procedure (continuous 

shaking), is 5 minutes. The time is longer when the can is not shaken and 15 minutes is 

insufficient to evaporate the complete content of the can in the upright position. Most cases that 

take longer than 20 minutes are done with more than 1 can. 

Charge operation duration

0

2

4

6

8

10

12

1 5 10 15 25 40

Minutes

Number of operations .

0%

5%

10%

15%

20%

25%

30%

35%

40%

Sample percentage .

Charge operation duration (20 cases)

0

1

2

3

4

5

6

7

8

9

10

1 5 10 15 25 40

Minutes 

Number of vehicles 

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

Sample percentage 

Figure 2.20 Refrigerant charging time (sample 1). Figure 2.21 Refrigerant charging time (sample 2). 

50% of Sample 1 SCUs charged the MVAC in the upright position (vapor phase only). This 

explains why the most frequent charging time is 15 minutes (see Figure 2.20). Only 30% of the 

operations took between 5 and 10 minutes. 

In contrast, 75% of Sample 2 SCUs charged while shaking the can from vertical to horizontal 

positions. The most frequent charging times are 5 and 10 minutes, which is consistent (see 

Figure 2.21). 40% of operations took 10 minutes and 35% took 5 minutes. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -36 -

Figures 2.20 and 2.21 indicate that two cases in Sample 1 and one case in Sample 2 completed, 

charging operations in only 1 minute. There are two reasons for the shortness of these 

operations: 

 The SCU reads the pressure gauge indicator and stops charging because the pressure 

seems to be correct. The charge with a small can is limited to the pressure equilibrium. 

In this case most of the refrigerant remains in the can. 

 The operator does not recognize how to proceed, so he stops the operation shortly after 

the beginning. 

 

Charge operation duration (50 cases)

0

2

4

6

8

10

12

14

1 5 10 15 25 40

Minutes

Number of operations 

0%

5%

10%

15%

20%

25%

Sample percentage 

The can is kept for a later use

yes

35%

no

65%

Figure 2.23 Part of people who keep the 

can after use. 

Figure 2.22 Refrigerant charging time (overall sample). 

Considering the charging time for the overall sample, nearly 50% took from 5 to 10 minutes. 5% 

took less than 1 minute and 5 % took more than 40 minutes. Cases where the charging process 

took 25 minutes are due to two reasons: vapor charging or more than one can has been 

charged. 

After the charging operation, some refrigerant may remain in the can, and especially when the 

can capacity is large, or when the charging operation is performed in vapor phase. When the 

SCU is using a small can equipped with a valve, the can is reusable. But in the case of 

perforated cans, refrigerant is completely released when disconnecting the can. According to 

the field survey, two thirds of SCUs declare they will not keep the can after use (see Figure 

2.23). 

2.3.5 Refrigerant emissions associated with the use of small cans 

Refrigerant emissions during the charging process 

As presented in Section 2.3, the total number of vehicles tested was 45 including the 16 vehicles 

owned by the SCUs and 29 operations being done on the CEP cars. 

The initial refrigerant content of the MAC system is known. The small can has been weighed 

before and after the charging process. The difference corresponds to the refrigerant mass 

released from the can: the first part is filled in the AC circuit; the second part is released during 

the charging process. 

Once the refrigerant recovery is performed, the precise system charge using the small can is 

measured by difference with the known initial charge (1/3 of the original charge). The difference 

between the refrigerant contained in the can (initial weighing), and the refrigerant mass really 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -37 -

filled in the MAC circuit is the refrigerant emission during the charging process, plus the 

refrigerant heel remaining in the can. 

Figures 2.24 to 2.29 illustrate emissions in grams (g) due to servicing the can heel as well as the 

overall emissions for the overall sample (45 cases). Results corresponding to Samples 1 and 2 

alone are presented separately in Annex B. 

Emissions due to servicing

0

2

4

6

8

10

12

14

16

18

0g to 5g

5g to 10g

10g to 50g

50g to 100g

100g to

250g 

250g to

500g

more than

500g

Number of vehicles 

0%

5%

10%

15%

20%

25%

30%

35%

40%

Sample percentage 

Emissions due to servicing

0

100

200

300

400

500

600

700

0g to 5g

5g to 10g

10g to 50g

50g to 100g

100g to

250g 

250g to

500g

more than

500g

g

0%

5%

10%

15%

20%

25%

Mass percentage 

Figure 2.24 Number of vehicles as a function of 

emission range due to servicing (overall sample). 

Figure 2.25 mass emission as a function of emission

range due to servicing (overall sample). 

Figure 2.24 presents the classification of operations as a function of emission range due to 

servicing for the overall sample composed of 45 operations. For 16 cases, representing 36% of 

the sample, small emissions have been observed: between 0 and 5 grams. 

A few charging operations (five cases, or 10%) were very leaky and lead to massive releases of 

refrigerant (over 100 g): 

 A great number of cans equipped with valves as well as some charging guns for S&P 

type (F1-13 illustrated in Section 1) are very leaky and are not very convenient to use. 

The valve is very leaky and frequently liquid refrigerant was released at the connection 

when the can is put upside down. 

 When the operator is using 2 or more “screwed type” small cans, the release of 

refrigerant remaining in the first can be significant, if the can is not empty (filling in vapor 

phase, without shaking). 

Figure 2.25 illustrates the emissions during servicing classified by emission ranges. Emissions 

from 0 to 10 g represent 54% of the sample. In contrast, these emissions represent only 4% of 

the total mass emitted during the charging process on a mass basis. 

The major part of emissions (64%) is due to high releases, over 100 g, which represents only 

five of the sample cases. One non-correct operation done without care could release as much 

as 20 correct operations. 33% of the overall mass emissions range between 10 and 100 grams. 

Refrigerant emissions the during charging process, which lead to a mass loss higher than 50 g, 

represent nearly 86% in mass of the total refrigerant emissions, but only 26% of the sample. 

The total mass emitted due to servicing represents nearly 16% of the sum of the refrigerants 

charged inside AC systems. 

Can heels 

At the end of the charging process, the refrigerant remains inside the can (valve equipped) or is 

released to the atmosphere if the charging kit is unscrewed (in case of S&P cans). Depending 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -38 -

on the charging process (shaking or not shaking the can, filling the AC system in the liquid or 

vapor phase) the refrigerant in the can heel is significant or not. 

Can heel

0

2

4

6

8

10

12

14

16

0g to 5g

5g to 10g

10g to 50g

50g to 100g

100g to

250g 

250g to

500g

more than

500g

Number of vehicles 

0%

5%

10%

15%

20%

25%

30%

35%

Sample percentage 

Can heel

0

500

1000

1500

2000

2500

3000

0g to 5g

5g to 10g

10g to 50g

50g to 100g

100g to

250g 

250g to

500g

more than

500g

g

0%

10%

20%

30%

40%

50%

60%

Mass percentage 

Figure 2.26 Number of vehicles as a function of can

heel range (overall sample). 

Figure 2.27 Mass emission as a function of can heel

range (overall sample). 

When the charging process is done correctly, the can is more likely empty at the end and the 

heel is low (between 0 to 10 g). This represents 31% of the operations that sensibly meet in the 

number of persons who did the operation correctly (32%). 

62% of operations are done with the can heel lower than 50 g, which represent only 7% of the 

total heel (see Figure 2.27). 38% of operations are not properly done (can heel is larger than 

50 g) but represent more than 90% of the overall can heel. The total heel resulting represents 

nearly 33% of the sum of the refrigerants filled inside AC systems. 

Overall refrigerant emissions 

Figures 2.28 and 2.29 illustrate the total refrigerant emissions coming from emissions due to 

servicing as well as from the can heels after charge, measured during the 45 operations 

performed by small can users. 

Total refrigerant losses 

0

2

4

6

8

10

12

14

16

0g to 5g

5g to 10g

10g to 50g

50g to 100g

100g to

250g 

250g to

500g

more than

500g

Number of vehicles 

0%

5%

10%

15%

20%

25%

30%

35%

Sample percentage 

Total refrigerant losses 

0

500

1000

1500

2000

2500

3000

0g to 5g

5g to 10g

10g to 50g

50g to 100g

100g to

250g 

250g to

500g

more than

500g

g

0%

5%

10%

15%

20%

25%

30%

35%

40%

Mass percentage 

Figure 2.28 number of vehicles as a function of total 

refrigerant emissions (overall sample). 

Figure 2.29 mass emission as a function of total 

refrigerant emissions (overall sample). 

Refrigerant emissions that are less than 10 g (13% of cases) represent a total refrigerant release 

of less than 1% on a mass basis (see Figure 2.29). Large releases of refrigerant (more than 250 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -39 -

g per operation) represent 43% of the sample observed (45 vehicles and small can users), but it 

represents 78% on a mass basis. 

Refrigerant mass repartition and ratios 

Sample 1 (25 cases) 

In Sample 1, the total mass of refrigerant contained in small cans before the charging operation 

is 14,395 g, corresponding to an average value of 575 grams per vehicle. The effective 

refrigerant mass charged in the vehicle is 8,557 g (342 g/vehicle) and represents 59% of the 

total initial mass. In contrast, the total refrigerant emissions due to servicing are 1,830 g 

(73 g/vehicle) representing 13% of the total initial mass. Moreover, the total can heel is 4,009 g 

(160 g/vehicle), which represents 28% of the total initial mass (see Figures 2.30 and 2.31). 

Refrigerant mass

0

2000

4000

6000

8000

10000

12000

14000

16000

Effective

mass charged

Leaks due to

servicing

Can heel SUM

Mass (g) 

0

100

200

300

400

500

600

Mean values per vehicle (g) 

Refrigerant ratio

59%

28%

13%

Effective mass charged

Leaks due to servicing

Can heel 

Figure 2.30 Refrigerant mass repartition (sample 1). Figure 2.31 Refrigerant ratio (sample 1). 

From the first sample, it could be concluded that DIYers who are not-familiar with small cans, 

lead to overall emissions of about 68% of what has been charged inside the MVACS. 

Sample 2 (20 cases) 

In contrast, when the DIYers are familiar with small cans, the overall emissions are about 21% of 

the effective mass charged. 

Refrigerant mass

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Effective

mass charged

Leaks due to

servicing

Can heel SUM

Mass (g) 

0

50

100

150

200

250

300

350

400

450

Mean values per vehicle (g) 

Refrigerant ratio

82%

11%

7%

Effective mass charged

Leaks due to servicing

Can heel 

Figure 2.32 Refrigerant mass repartition (sample 2). Figure 2.33 Refrigerant ratio (sample 2). 

For sample 2, the total mass of refrigerant contained in small cans before the charging operation 

is 7,626 g, corresponding to an average value of 381 g/vehicle. The effective refrigerant mass 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -40 -

charged in vehicles is 6,280 g (314 g/vehicle) and represent 82% of the total initial mass. In 

contrast, the total refrigerant emissions due to servicing are 512 g (25 g/vehicle) representing 

7% of the total initial mass. Moreover, the total can heel is 834 g (41 g/vehicle), which 

represents 11% of the total initial mass (see Figures 2.32 and 2.33). 

Overall sample (45 cases) 

Considering the overall sample, that covers a wide range of randomly chosen people, the values 

obtained are in the middle between those obtained for Samples 1 and 2. Overall emissions are 

about 48% of the effective mass charged. 

Refrigerant mass

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

Effective

mass charged

Leaks due to

servicing

Can heel SUM

Mass (g) 

0

50

100

150

200

250

300

350

400

450

500

Mean values per vehicle (g) 

Refrigerant ratio

67%

22%

11%

Effective mass charged

Leaks due to servicing

Can heel 

Figure 2.34 Refrigerant mass repartition (overall 

sample). 

Figure 2.35 Refrigerant ratio (overall sample). 

The total mass of refrigerant contained in small cans before the charging operation is 22,021 g, 

corresponding to an average value of 490 g/vehicle. The effective refrigerant mass charged in 

vehicles is 14,837 g (330 g/vehicle) and represents 67% of the total initial mass. In contrast, the 

total refrigerant emissions due to servicing are 2,341 g (52 g/vehicle) representing 11% of the 

total initial mass. Moreover, the total can heel is 4,842 g (108 g/vehicle), which represents 22% 

of the total initial mass (see Figures 2.34 and 2.35). 

Values to remember 

 67% of initial mass contained in the cans are effectively charged into the system, 

 11% are directly emitted during the charging procedure, 

 22% remain in the can as heel. Sooner or later, they will be released to the atmosphere. 

3. Analysis of current leak search and recharge by professional servicing in 

California 

3.1 Introduction 

The aim of this section is to analyze the refrigerant leak search as well as the recharging 

procedure done by professional servicing in California. In fact, a consumer unfamiliar with auto 

servicing, whose MAC system presents a partial or full failure, will mandate a professional in 

order to repair it. 

A MAC failure on a CEP car has been simulated by having an empty or partially empty system. 

The overall professional procedure is described step by step from the preliminary AC check until 

the charge of the system. The operating mode of the service technician will be carefully 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -41 -

described. After the charge, the CEP team recovers carefully the refrigerant in order to evaluate 

the accuracy of the recharge compared to the original system charge. 

50 garages or AC repair centers have been considered in different areas in California in order to 

cover a wide range of cases. Garage visits and operations are detailed in Annex C. 

3.2 Operating procedure to perform professional servicing analysis 

3.2.1 Simulation of AC failure 

A first proposal was to use rental cars to proceed and analyze the current professional servicing. 

Due to regulations, the CEP team was not allowed to use such vehicles nor operate on the AC 

system. 

The first two operations were done using the CEP Cadillac Deville. The CEP team was obliged 

to use a different vehicle for the following reasons: 

 as mentioned previously, the Cadillac AC system ran originally with R-12 refrigerant and 

had been retrofitted to R-134a 

 two leaks were detected, the first one on the HP service valve, the other one on the 

compressor suction port 

 after visiting two garages, the compressor clutch stopped operating. 

Note: one professional declined to make any repair on this system (because of the retrofit from 

R-12 to R-134a); thus, when a professional declines, the only way for charging such a system is 

to use small cans. 

For this reason, the CEP team had to buy a vehicle running on R-134a. All other visits (48 visits) 

at professional garages have been made using the CEP Mitsubishi Montero. 

Two criteria motivated the choice of the Mitsubishi. The first and main criterion is the 

accessibility of the high and low-pressure servicing valves. The second one is the large cargo 

space available in the Mitsubishi Montero, which has been very useful to carry the CEP 

equipment. 

In order to ask mechanics to repair the system, failure had to be simulated. The failure 

organized by the CEP team simulated real operating defaults of the MAC system. Two failures 

have been considered and are described below. 

 The CEP team partially charged the MAC system with refrigerant. The mean refrigerant 

mass charged is around 100 grams. The MAC system did not present any leakage, rupture 

or malfunctioning. 43 cases were considered partially empty. 

 The other 7 cases were similar to the first ones, but the system was emptied down to 

residual pressure equal to atmospheric pressure. 

3.2.2 Description of the MACS used 

The Mitsubishi Montero AC is a single-evaporator system using a thermal expansion valve with 

a parallel flow condenser and a fixed displacement compressor. The HP and LP service valves 

are easily reachable as shown in Photo 3.1. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -42 -

The arrangement of AC components is also indicated on Photo 3.1. A scheme of the Montero 

AC system is shown in Figure 3.1. 

Photo 3.1 Under hood view showing the arrangement of the AC system components. 

Figure 3.1 Schematic view of the Mitsubishi Montero AC system. 

The potential leak sources on the Montero AC system are circled in red on Figure 3.1 and are as 

follows: 

 The compressor rotating lip seal 

 The compressor suction and discharge ports 

 The inlet and outlet of the condenser, evaporator, and TxV 

 The liquid receiver inlet and outlet 

 The HP and LP service valves 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -43 -

 Fittings on the suction line and on the liquid line 

 The high-pressure sensor 

 The relief valve 

Using an electronic detector, the CEP team performed a leak search on the MACS in order to 

check the system leak tightness. All parts and connections are verified. The whole system is 

tight except at the TxV where a very small leak is detected. 

3.2.3 Selection of professional garages and sample description 

50 garages have been visited in California. Garages are located in different areas in order to 

collect a wide sample, especially in Los Angeles and San Diego (see Figure 3.2). 

Figure 3.2 Location of garages visited in California. 

Garage size (50 cases)

0

2

4

6

8

10

12

14

16

18

20

22

24

26

N <= 2 2 < N < 5 N >= 5

Number of cases 

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

Sample percentage

 

Figure 3.3 shows the repartition 

of garages by size (technician 

number). 38 % of garages 

consist of 2 or 1 technicians. 

46 % have 3 or 4 technicians. 

The remaining 16% have 5 

technicians or more. 

N: Number of technicians

Figure 3.3 Garage sizes based on the number of technicians. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -44 -

3.3 Analysis of current leak search and recharge by professional servicing 

3.3.1 Preliminary AC check by professional servicing 

The servicing technician usually makes a first AC check before completing any operation on the 

system. When the CEP team car is in the garage for servicing, the professional makes a 

preliminary AC check. The goal of this check is to make a first diagnosis on the failure cause. 

After this preliminary check, the servicing technician indicates a first diagnostic with a cost 

estimate. The client is subsequently free to accept or refuse the recommended actions. 

This first check up could include: 

 verification of the blown air temperature in the cabin, 

 control of the compressor clutch, 

 measurement of the low and high pressures (AC on),

 analysis of refrigerant using an electronic analyzer plugged on to the service valves, 

 verification of the pressure inside the AC loop by pressing the HP or LP valves. 

 

Figure 3.4 illustrates the actions made by the professionals before doing any operation on the 

system (actions done before giving any diagnosis). 

Preliminary AC check (50 cases)

0

5

10

15

20

25

30

35

40

45

air

temperature

Comp clutch HP LP Refrigerant

analysis

Press

shrader

Number of cases

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Sample percentage

Figure 3.4 Preliminary AC check. 

68% of professionals immediately check the blown air temperature in order to verify the 

availability of the fan and the coldness. two-thirds of the professionals directly verify the 

compressor clutch by visualizing or by hearing that it is ON. 

80% verify the low pressure and 76% verify the high pressure inside the system using a manifold 

when the AC is running. The difference between the two pressures in running mode (HP and 

LP) is an indirect way to check that the clutch is ON. In contrast, when the engine and the AC 

are OFF, the pressure check indicates if any refrigerant remains. 

Other actions have been noted: the analysis of the refrigerant (7 cases), and pressing the 

Schrader valve in order to verify that refrigerant is released (6 cases). It should be mentioned 

that the preliminary AC check could combine two or more verification types. 

After doing these preliminary checks, professionals give a first diagnosis (see Figure 3.5). The 

primary action recommended was a recharge of the AC system (94% representing 47 cases). In 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -45 -

34 cases the advice given to the CEP team was to check the leak tightness (68%). It should be 

noted that in only 76 percent of these cases was the system checked for leaks. 

Preliminary diagnostics and advices (50 cases)

0

5

10

15

20

25

30

35

40

45

50

Leak check recharge Change

compressor

Buy SC 

Number of cases

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Sample percentage

Figure 3.5 Preliminary diagnosis and recommendations. 

Three particular cases should be mentioned: 2 garages recommended the CEP team change 

the compressor (note: these two recommendations were made for the Mitsubishi), the third one 

recommended buying small cans from an auto-parts store and recharge the AC. 

3.3.2 Leak search and recharge by professional servicing 

Depending on the diagnosis and the estimate given by the professional, the CEP team then has 

the choice to accept or decline the recommended actions. 

When the professional is requested to operate on the vehicle, two evaluation steps are then 

performed. The first one is the leak search and the second one is related to the charging 

procedure. 

Leak search procedure evaluation 

Among the 50 technicians met only 47 have operated on the system. The three other cases are 

those who advised the CEP team to change the compressor or to buy SC from an auto-parts 

store. 

First actions done (47 cases)

0

5

10

15

20

25

30

35

40

45

Evacuate to

atmosphere

vaccum

recharge

Recover and

recycle vaccum

recharge

keep the initial

charge

add refrigerant

to initial charge

Add DYE

Number of cases

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Sample percentage

Figure 3.6 Small can users - Sample 1 description. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -46 -

The CEP team noted that four types of main first actions are performed when the servicing is 

accepted. These actions are classified as follows (see Figure 3.6): 

 The technician releases the refrigerant to the atmosphere, evacuates the system and 

recharges it (4 cases) 

 The technician recovers the refrigerant, recycles it with an automatic machine, evacuates 

the system, and recharges it partially or completely (24 cases), 

 The technician keeps the system untouched with the remaining charge (7 cases), 

 The technician adds refrigerant to the remaining charge done by CEP (13 cases). 

Whatever the method of operation, 26 technicians among the 47 have added dye to the system 

using the automatic group or a special charging kit. In addition to the fact that those 26 

technicians have added dye, some of them did not perform the leak check. In fact, those 

technicians requested the CEP team to come back later for a leak search with a fluorescent 

detector (20 cases). 

Even though 34 technicians have recommended verifying the leak tightness as a first diagnosis, 

only 26 have performed the leak check (see Figure 3.7). In all cases, 5 methods are indicated: 

 Controlling the rise of the vacuum pressure (7) 

 Direct UV detection (22) including 3 technicians who noticed that the system is already 

charged with dye 

 Later UV detection (20) 

 Electronic detection (14) 

 Pressurized air or CO2 with soap bubble (2). 

Leak search method (26 cases)

0

5

10

15

20

25

30

Control rising

vaccum

pressure

Direct UV

detection

Later UV

detection

electronic

detection

Pressurized 

air or CO2

soap bubble

Number of cases

0%

20%

40%

60%

80%

100%

Sample percentage

Figure 3.7 Leak search methods. 

Note: Technicians who used soap bubbles to detect the leak are those who filled the system with 

pressurized air or CO2. The technicians who used CO2 proceeded later with a UV detection 

after releasing the CO2 to the atmosphere, then charging with R-134a + DYE. 

Several methods could be combined in order to verify the leak tightness of the system. When 

using an automatic charging machine, the pressure rise after evacuation is easily controlled 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -47 -

(automatically). For UV detection, it is easier to add oil including dye. An electronic check could 

be also done later. The leak search time is directly related to the good will of the professional 

who does the servicing. If he spends more time searching leaks, the probability of forgetting 

potential leaks decreases. 

Two technicians performed a careful leak search, spending the necessary time for that. 13 

technicians have done it in less than 10 minutes. The 11 others took from 10 to 20 minutes (see 

Figure 3.8). 

Leak search time in minutes (26 cases)

0

5

10

15

20

25

30

t < 10 10 < t < 20 t > 20

Number of cases

0%

20%

40%

60%

80%

100%

Sample percentage

Figure 3.8 Leak searching time. 

Among the 26 technicians who did the leak search, 8 of them found leaks (see Figure 3.9). But 

the leaks found do not correspond to those detected by the CEP team at the TxV connection. In 

fact, most of the cases were traces of UV at several sites: 

 4 leaks are detected at the service valves, 

 3 leaks are detected at the suction line, 

 1 leak on the condenser. 

Leak detection (26 cases)

0

5

10

15

20

25

30

detect leak Do not detect a leak Check evaporator leak

Number of cases

0%

20%

40%

60%

80%

100%

Sample percentage

Figure 3.9 Leak detection. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -48 -

Concerning the three technicians who found a leak on the suction line, one of them advised the 

CEP team to change the complete line, the second one to change the seal of the fitting, while 

the third one who found a leak on the suction port of the compressor, advised the team to 

change the line and the compressor. Of course, the CEP team declined doing that. The 20 

other professionals did not detect any leak. None of the professionals detected the leak at the 

TxV. 

It should be mentioned that 8 technicians verified the leak tightness of the evaporator by opening 

the evaporator box. 

Recharge procedure evaluation 

Among the 50 garages considered at the beginning, 40 have charged the system with 

refrigerant. The 10 others who did not charge the system made the following comments: 

 1 technician said that the system was overfilled with oil (garage number 4) 

 1 technician advised to buy a SC (garage number 7)

 3 garages number 8, 11, 48 have given only advice 

 1 technician advised to buy a Schrader from an auto-part store (garage number 9) 

 2 technicians advised to change the compressor (garages number 22, 49) 

 2 technicians detected the leak at the suction line. The first recommended changing the 

line, the other one to change the suction seal (garages number 43, 40). 

Operation (50 cases)

0

5

10

15

20

25

30

35

40

45

Charge the system Did not charge the

system

nominal charge

acknow ledge 

operation ID sticker

Number of cases

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Sample percentage

Figure 3.10 Recharge procedure. 

Before charging the system with refrigerant, 34 technicians read the nominal charge indicated by 

the manufacturer under the hood. This information is crucial if the professional wants to exactly 

charge the system properly. 

An important point has to be mentioned: only 4 professionals marked their operation by putting a 

sticker under the hood indicating the date of operation and the mass of refrigerant charged. 

Three methods are used by professionals to charge the refrigerant in the system according to 

the equipment available in their garage. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -49 -

 The use of an automatic machine successively doing the recovery and the recycling, the 

evacuation and the charge. 29 out of the 40 who did the recharge used automatic 

machines. 

 The use of a refrigerant cylinder with a manifold and vacuum pump. 13 used this method 

but not all of them used the vacuum pump. 

 The use of small cans to only charge the system, with neither recycling nor evacuation. 

In fact they only complete the charge (5). 

Forty technicians performed the refrigerant charge (see Figure 3.11). Two of them made a 

complementary charge with small cans, the first using an automatic charging machine and the 

other using the cylinder and manifold. The first used the small can because he wanted to add a 

stop leak (4 oz), the other one added oil (SC 12 oz + oil). 

Charging method (40 cases)

0

5

10

15

20

25

30

35

Automatic machine cylinder + manifold Small can

Number of cases

0%

10%

20%

30%

40%

50%

60%

70%

80%

Sample percentage

Figure 3.11 Charging methods. 

Twentysix technicians added dye when charging the system. Twentyfour added oil to the 

system either by using an automatic machine or by injecting the oil directly with a specific 

charging kit. 1 technician charged with a small can including a “stop leak” additive. 

Additives (40 cases)

0

5

10

15

20

25

30

DYE Oil Stop leak with SC

Number of cases

0%

10%

20%

30%

40%

50%

60%

70%

Sample percentage

Figure 3.12 Additives. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -50 -

In order to evaluate the refrigerant charges done by the professionals and compare it to the 

original charge indicated by the manufacturer the CEP team analyzed the precise recovery of 

refrigerant from the MAC system after each visit. 

The technicians who charged are classified into four groups (see Figure 3.13). 

 In blue those who charged with an automatic machine 

 In green those who charged with a cylinder and a manifold. 

 In orange those who charged with small cans 

 In red those who combined two methods 

Note: the red line indicates the manufacturer nominal charge of the vehicle (680 grams). The 2 peaks 

shown correspond to the 2 cases performed with the Cadillac. 

0

100

200

300

400

500

600

700

800

900

1000

13

101215161920212324252627282930313234353637383941424713141833444546

256

5017

Garage Number

Refrigerant charge (grams)

0

100

200

300

400

500

600

700

800

900

1000

Figure 3.13 Refrigerant charge recovered for all professionals. 

In Figure 3.13, the black dots represent those technicians that did not check the nominal 

refrigerant charge specified by the manufacturer. The first reason is the precision of the 

automatic machine. The second reason is that some professionals do not respect the 

manufacturer charge even if they read it before. 

Those technicians who charged with a cylinder/manifold combination did not use a scale to 

weigh the refrigerant charge. 

Garage number 44 released the charge to the atmosphere. Initially, the system was empty, so 

he charged the system without prior evacuation. The pressure increased when he ran the AC 

and the relief valve released the refrigerant. The same story occurred with garage number 46. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -51 -

The summary of operations and actions during the 50 visits are presented in Figure 3.15. 

Interventions price

$0

$50

$100

$150

$200

$250

123456789

1011121314151617181920212223242526272829303132333435363738394041424344454647484950

Garage number

Price in USD

Figure 3.14 Prices as a function of garages and operation. 

50 

garages 

47 

first actions & 

diagnostics

3 

diagnosis failure

18 

recharge 

only 

4 

Leak search 

only 

22 

Leak search 

& recharge 

3 

advices 

26 

Leak search 

40 

Recharge 

Figure 3.15 Operation summary. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -52 -

4. Laboratory Testing 

4.1 Evaluation of potential leak sources of professional servicing 

The aim of this section of the study is to first evaluate the potential leak sources of refrigerant 

while a professional is intervening on the AC system. The second purpose is to recommend a 

series of actions to be done in order to ensure proper and less leaky maintenance. 

4.1.1 System performances related to refrigerant charge 

The cooling performance evolution of one of the 5 MAC systems studied in Section 1 is analyzed 

along a leaking process. A controlled slow leak is simulated when the MAC system is operating 

in a steady state regime. The tests are performed at the CEP laboratory using its MAC test 

bench (Photo 4.1). 

Photo 4.1 General view of the test bench. Photo 4.2 Leak valve with micro counter. 

The leak is controlled using a micro-counter precise valve (see Photo 4.2). The LFR is about 

1.34 g/min. The leak is determined by weighting the recovered refrigerant in a cylinder 

connected to the low-pressure service valve. 

The leak process begins when the steady state regime is reached: the leak valve is opened, the 

leak begins and continues until performance starts to decrease (very low cooling capacity, very 

high superheat, very low evaporating and condensing pressures). The leak test process takes 

place over 7 hours. 

The system is charged at the beginning of the test with 700 grams of refrigerant. The mass of 

refrigerant, recovered 7 hours later, is 130 g. 

The temperature is maintained at 30°C at the evapor ator inlet. The air temperature equilibrium 

at the condenser inlet is 33°C. Tests are performe d at 1000-rpm compressor speed; the air 

mass flows on the condenser and evaporator are respectively 420 and 1540 m3

/h. 

Figures 4.1 and 4.2 show respectively the condensing pressure and the sub-cooling evolutions 

as a function of the refrigerant charge. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -53 -

Condensating pressure evolution

0

200

400

600

800

1000

1200

1400

1600

1800

2000

700 600 500 400 300 200 100

Refrigerant charge [gr]

Condensating pressure [kPa]

Subcooling evolution

0

2

4

6

8

10

12

14

16

18

20

700 600 500 400 300 200 100

Refrigerant charge [gr]

Subcooling [K]

Figure 4.1 Condensing pressure evolutions. Figure 4.2 Sub-cooling evolutions. 

Figures 4.3, 4.4 and 4.5 show respectively the evaporating pressure, the superheat, and the 

supply air temperature evolutions as a function of the refrigerant charge. 

Evaporating pressure evolution

200

220

240

260

280

300

320

340

360

700 600 500 400 300 200 100

Refrigerant charge [gr]

Evaporating pressure [kPa]

Superheat evolution

0

4

8

12

16

20

24

28

32

36

700 600 500 400 300 200 100

Refrigerant charge [gr]

Superheat [K]

Figure 4.3 Evaporating pressure evolutions. Figure 4.4 Superheat evolutions. 

Supply air temperature

8

10

12

14

16

18

20

22

24

26

28

700 600 500 400 300 200 100

Refrigerant charge [gr]

Temperature [°C]

Figure 4.5 Blown air temperature evolutions at the 

evaporator outlet. 

As seen in Figures 4.1 to 4.5 , three phases could be considered: 

o The first phase corresponding to a system charge varying from 700 to 520 grams 

o The second phase corresponding to a system charge varying from 520 to 340 grams 

o The third phase corresponding to a system charge varying from 340 to 130 grams. 

The first phase corresponds to the case where the liquid receiver still contains refrigerant in 

liquid phase whatever the remaining quantity. In this case, the system performance remains 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -54 -

constant independent of the refrigerant quantity. All properties are unchanged, especially the 

cooling capacity. 

The second phase corresponds to the case when there is no more liquid in the receiver, and that 

sub-cooling is fairly small. It has to be noticed that the sub-cooling decreases along the leaking 

process (see Figure 4.2), the superheat increases linearly (see Figure 4.4), and the air 

temperature at the evaporator outlet increases slightly (see Figure 4.5), meaning that the user or 

the mechanic cannot diagnose refrigerant loss under those temperature conditions. 

The third phase is reached when the refrigerant charge is low. The heat exchangers are then 

oversized, and the condensing pressure decreases. The mass flow rate decreases at the TxV. 

The superheat and the air temperature at the evaporator outlet increase rapidly. The 

temperature level indicates the need for refrigerant recharge. 

The system tested is equipped with a thermal expansion valve (TxV) and a fixed displacement 

compressor working in a steady state regime. For MAC system equipped with an orifice tube 

expansion valve (OT), the variations of pressures are more sensitive to the refrigerant charge, 

especially during the first phase. 

Concerning the user, the only parameter to evaluate the system operation is the blown air 

temperature. According to Figure 4.5, no significant changes to the blown air temperature can 

be detected before losing about 50% of the refrigerant charge (340 grams). 

4.1.2 Potential leak sources during a typical maintenance procedure 

During a classic maintenance procedure performed by a technician, the potential emissions are 

related to: 

- connection and disconnection of the recovery equipment to the service valve 

- connection and disconnection of the charging cylinder or a small can 

- rough verification of refrigerant charge by triggering the service valve 

- direct evacuation of the MAC system without recovery 

- emissions, when dismounting a component, if the recovery procedure has not been 

accomplished properly. 

Significant emissions are due to direct evacuation and release of refrigerant from a small can, 

when not properly charged in the MAC system (the remaining quantity in the can, the “heel” is 

significant). 

First operations done on the system before a leak search could be divided in four actions. 

According to Figure 3.15, the main action done is the use of automated recovery machine, which 

recovers, recycles, evacuates, and recharges (48% of the visited garages). 

The second main action consists of adding refrigerant to the initial charge usually using cylinder 

and manifold or small cans (24%). 

The third case is to keep the initial charge when searching the leak (14%). 

The last case is the evacuation into the atmosphere in order to evacuate the refrigerant and 

recharge (8%). 

Note: in the first case, all technicians have recovered the refrigerant before making a leak 

search, which is clearly wrong because the driving force of the leak is the refrigerant pressure 

inside the MAC system. . 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

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Service valves 

In fact, each time the service valves are used a leak occurs. The refrigerant quantity released is 

random and depends on the professional actions and equipment used. The leak is estimated 

usually in between 2 to 5g. Undue verification of refrigerant pressure by pushing the Schrader 

mechanism of the service valve may lead to emissions of up to 10 to 15 g. 

When a professional connects the recovery equipment or cylinder using a quick coupler with 

moving rod, emissions are usually lower compared to connections fastened with a fixed rod. 

Photo 4.3 shows a quick coupler with a moving rod. When turning the valve, the rod moves to 

push the Schrader valve of the service valve. The leak tightness is assured before the Schrader 

is pushed down and to make the connection. In fact, these connections are connected first to 

the service valve and then the gates are screwed and opened. 

In contrast, the quick couplers with a fixed rod open the gates at the moment they are 

connected. Photos 4.4, 4.5, and 4.6 show three types of quick coupler with fixed rod fastened 

with clips. 

Photo 4.3 Quick coupler - Connection with 

moving rod by screwing fastened with clips. 

Photo 4.4 Quick coupler - connections with fixed rod 

fastened with clips equipped with ball valve. 

Photo 4.5 Quick coupler - connections with fixed 

rod fastened with clips. 

Photo 4.6 Quick coupler - connections with fixed rod 

fastened with clips. 

For couplers with a fixed rod, the tightness of the operation is random and dependent on the 

technician skills operating the system. If the Schrader valve is pushed straight, the valve will 

leak less or not leak at all. In contrast, if the Schrader is wrongly pushed, it will leak 

unexpectedly. 

Clearly, the couplers with moving rods leak less. The coupler is first fixed on the service valve, 

the valve is then turned in a way to move down the rod and open the gate. The professional 

could check the way the valve is installed before opening the Schrader. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -56 -

The charging method 

The charging method is a potential source of refrigerant leak. As shown in Section 3.2.2, 

professionals can use three methods to charge a MAC system: 

- with automated machines (72.5%) 

- with cylinder + manifold (20%) 

- with small cans (7.5%). 

Usually, the automated machines perform 

the whole procedure without action by the 

professional (recovery, evacuation, leak test, 

and recharge). The machine is connected to 

the system via HP and LP service valves. 

The quick couplers used are usually with a 

moving rod, allowing good leak tightness. 

The connection between the machine and 

the system is set once. 

Photo 4.7 Automated machine in service. 

The major emission occurs at the connection valves (assuming that the machine is tight 

enough). Each time a hose is installed or removed, a small emission occurs. For this reason, 

the use of an automated machine leads to lower emissions because there are only 2 connecting 

actions on the HP and LP pressure service valves, and 2 disconnecting actions, which constitute 

the smallest number of connecting / disconnecting actions. 

Another conventional method consists of using 

successively: 

- a recovery machine, 

- a recovery cylinder, 

- a manifold, 

- a vacuum pump. 

So the possible number of connecting /disconnecting

actions could be as high as ten, and thus refrigerant 

emissions are higher. 

Photo 4.8 Recovery machine and cylinder.

Recovery efficiency and evacuation 

Whatever the method used, the recovery machine allows recovering refrigerant at a specified 

limit (~4.3 psi absolute). The remaining refrigerant in the system cannot be recovered and so it 

is released to the atmosphere when using the vacuum pump. 

The vacuum pump releases the refrigerant or air remaining in the system to the atmosphere. 

The remaining quantity of refrigerant depends on the recovery pressure limit, temperature, and 

the system internal volume. Typically, this quantity varies from 10 to 100 g depending on the 

fixed low-pressure threshold. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -57 -

4.1.3 Recommended service procedure 

In fact, a user goes to a garage for MAC servicing in two cases: the AC system is working poorly 

or not working at all. The reasons for such malfunctioning could be mechanical failure of the 

compressor or other components (evaporator blower, condenser fan, electronic command) or 

low refrigerant charge in the system. The professional should identify, by inspection, the 

source(s) of malfunctioning before connecting any hoses to the service valves. 

As mentioned in the MACS (Mobile Air Conditioning Society) report on “recommended air 

conditioning inspection and preventive maintenance procedures”, the following steps have to be 

done leading to efficient and effective operation: 

 Inspect the coldness of blowing air 

 Inspect the compressor drive belt and clutch 

 Inspect the flexible hoses and metal lines for signs of leakage or damage 

 Inspect the compressor for signs of possible shaft seal leakage 

 Inspect and clean the front of the condenser 

 Check operation of all fans, blowers, air filters, and air circulation 

 Check the functioning of the heater control valve (if any). 

Once the mentioned actions are performed without any observations indicating the cause of 

failure, the professional can then operate on the system by measuring the pressure in order to 

confirm the presence of refrigerant. 

1) AC OFF 

When the AC is OFF, the pressure at the equilibrium phase is related to the ambient 

temperature and not to the refrigerant charge. In contrast, with a single-phase presence the 

pressure is related to both: refrigerant charge and ambient temperature. When the pressure is 

lower than the saturation at the corresponding ambient temperature, that means the system is 

filled only with the gas phase. To conclude, when the AC is OFF the system pressure indicates 

two cases: 

 A partially empty system with gas phase (lower than saturation pressure or near atmospheric 

pressure). 

 A partially or correctly filled systems if the pressure equals the saturation pressure. 

So when the AC is OFF, the only conclusion that can be drawn from the value of internal 

pressure is associated with a nearly empty system (without any more liquid). It cannot indicate 

the quantity of refrigerant when any liquid phase is still in the system. 

2) AC ON 

The measurement of evaporation and condensing pressures indicates the functioning of the 

compressor. Moreover, it could be useful to estimate the refrigerant charge in the system by 

comparing the thermodynamic properties as shown in Figures 4.1 to 4.5. 

Note: the only way to acknowledge the correct charge is to determine the sub-cooling: 

Sb = Toutlet condenser – Tsat (condensing pressure) requires not only pressure measurement but also 

precise temperature measurement at the condenser outlet. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -58 -

To conclude 

 If the AC failure does not concern the refrigerant system (e.g. fan, air circulation, belt...etc), 

the professional should not operate on service valves 

 The first action concerning the refrigerant should be leak search before recovery

 If the preliminary tests are carried out, the professional could then operate on the service 

valves in order to check pressures in standstill and in operation modes 

 To recharge the system, the lowest emissions during servicing are obtained when using an 

automated machine with a quick coupler equipped with a moving rod 

 The lower pressure threshold of the recovery machine pressostat has to be set as low as 

possible (typically 4.3 psi abs.); many are set just under atmospheric pressure (10 to 14 psi 

abs) 

 For large leaks (> 40g/yr), the pressure raise after deep evacuation could be a correct 

method provided the oil is hot ( T > 50°C) in order to avoid refrigerant outgasing from the oil 

 The leak search using either dye and UV lamp or electronic hand leak detectors are both 

acceptable methods (see Section 4.3), but only the wrapping method allows for detection of 

partial leaks in the range of 5 to 15 g/yr 

 In the presence of a leak, the fluid is recovered in order to repair the leak. In the absence of 

a leak, the fluid is recovered and refilled with the appropriate refrigerant charge. 

4.2 Leak tightness tests of brand new and after use small cans 

4.2.1 Introduction 

The reference technique for DIYers to recharge a mobile air-conditioning (MAC) system is to 

connect a small can to the system. The small cans are filled with refrigerant, currently 

HFC-134a, but may contain lubricant, dye, and sealant. Both DIYers and professional 

technicians use these small cans. 

Section 4.2 is dedicated to the laboratory measurements of refrigerant emissions from small 

cans before and after the first use. 

The leak flow rate (LFR) is measured using an infrared spectrophotometer that continuously 

records the refrigerant concentration raise inside an accumulation volume where the can has 

been installed. The test method is identical to the one defined by the European Regulation 

706/2007. 

The leaks of 15 can samples have been measured before and after the first use, at three 

different temperatures making a total of 90 leak tests. Tests have been performed at the CEP 

laboratory. Tests show that refrigerant emissions depend strongly on the can and charging kit 

sealing technologies. 

4.2.2 Description of small cans 

A small can consists of a sealed casing that contains a pressurized refrigerant that will be 

transferred to a MAC system by means of a valve and a flexible hose, the charging kit. This can 

is usually built by assembling three different metallic parts: a jacket, a valve plate, and a bottom 

plate. The can leak tightness is achieved by placing an elastomer seal between the valve plate 

and the jacket, as well as a rolled edge seal on the bottom plate (see Photo 4.9). 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

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Valve plate 

Jacket 

Bottom plate 

Elastomer seal 

Rolled edge seal 

Photo 4.9 Small can main components.

The two families of small cans are defined by the valve technology: 

 A self-closing valve inserted in the valve plate (type V, see Photo 4.10), or 

 A valve, which is screwed and perforates the valve plate (type S&P, see Photo 4.12). 

The charging kits also include a flexible hose connecting the small can to the air-conditioning 

system. The flexible hose and its low-pressure fitting are not considered in this leak test study 

since they are free of refrigerant before and after a partial use. 

The self-closing valve cans are available in 14 oz and 19 oz capacities. The self-closing valve 

is installed in the valve plate (see Photo 4.10) and tightened with an elastomer seal (see Photo 

4.11). An actuator pushes the stem downward (see Photo 4.11) and the refrigerant is released 

to the flexible hose. When the user stops acting, the stem closes and the container remains 

sealed. 

Stem 

Elastomer 

seal 

Actuator 

Photo 4.10 Valve plate with a self-closing valve. Photo 4.11 Sectional view of a self-closing valve 

actuator. 

The screwed and perforated cans have a different valve plate that incorporates an externally 

threaded portion coupled with the valve plate (see Photo 4.12). This portion has a wall that will 

be penetrated by the pointer of a valve. The S&P cans are available in different capacities: 12, 

13, 14, and 18 oz. 

Two different valve technologies can be found in S&P cans: 

 the shut-off valve, and 

 the push button valve. 
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The shut-off valve is screwed on the can valve plate (see Photo 4.12). After that, the user turns 

the handle and the pointer moves downward and penetrates the valve plate wall releasing the 

refrigerant. To isolate the container, the user must continue turning the handle until the pointer 

reaches the maximum displacement and contacts the valve central body. Valve isolation is 

achieved by using an elastomer seal between the valve and the container valve plate, and a 

metal-to-metal contact between the pointer and the valve central body (see Photo 4.13). 

Handle 

Pointer 

Metal-to-metal

seal 

Elastomer 

seal 

Photo 4.12 Valve plate of an S&P can. Photo 4.13 Sectional view of a shut-off valve. 

The push button valve is also screwed on the can valve plate but has a different perforating 

mechanism from the shut-off valve. As the user screws the valve, a pointer penetrates the valve 

plate wall and the refrigerant automatically flows to the valve. The valve is tightened by four 

different seals (see Photo 4.15). When the handle is squeezed, the refrigerant is transferred to 

the flexible hose and once the handle is released, the valve and the container are isolated. 

Elastomer 

seals 

Handle

Photo 4.14 Rubber seal and pointer 

of a push button valve. Photo 4.15 Sectional view of a push button valve. 

The seal is the weakest link not only in the refrigerant container, but also in the charging kit. 

Seal performance depends on different variables, such as the surface topography, the seal 

material properties, the seal design, and the applied load. Accordingly, it is expected that, as the 

number of seals increase, the refrigerant emissions also increase. 
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Tables 4.1 and 4.2 list a large variety of small cans and charging kits available on the California 

market, their type, content, market price, and on-line net price. A list of small cans and their 

characteristics are presented in Annex A. 

Table 4.1 Details of tested small cans. 

Brand Name Fitting type Capacity (g) Contents CEP 

reference Notes 

Interdynamics Valve equipped 510 R-134a + lubricant + leak 

sealer C1-01 No rolled edge seal 

Interdynamics Valve equipped 510 R-134a + lubricant + leak 

sealer C1-02 No rolled edge seal 

Interdynamics Valve equipped 396 R-134a + lubricant C1-04 

Interdynamics Valve equipped 397 R-134a + lubricant + leak 

sealer C1-06 

Interdynamics Valve equipped 398 R-134a + lubricant C1-07 

Interdynamics S&P 396 R-134a + lubricant + leak 

sealer C1-03 

Interdynamics S&P 396 R-134a + lubricant C1-05 

Interdynamics S&P 396 R-134a + lubricant + leak 

sealer C1-08 

Interdynamics S&P 398 R-134a + lubricant + leak 

sealer C1-10 

Interdynamics S&P 368 R-134a + lubricant + leak 

sealer C1-13 

Technical 

Chemical Co S&P 340 R-134a C3-01 

Technical 

Chemical Co S&P 340 R-134a C3-02 

Technical 

Chemical Co S&P 340 R-134a + leak sealer C3-03 

EF Products S&P 538 R-134a + lubricant + leak 

sealer C4-01 

EF Products S&P 538 R-134a + lubricant + leak 

sealer C4-02 
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Table 4.2 Details of tested charging kits. 

CEP 

reference Fitting type Photo 

F1-01 Valve 

equipped 

F1-02 S&P 

F1-03 S&P 

F1-04 S&P 

F1-05 S&P 

F1-07 S&P 

CEP 

reference Fitting type Photo 

F1-09 S&P 

F1-11 S&P 

F1-12 S&P 

F1-13 S&P 

F4-02 S&P 

As indicated above, two series of tests have been performed on the two families of small cans: 

the first series on the brand new small cans, and the second series after a first use of the small 

cans. 

The S&P cans are cheaper than those with valve or valves plus a pressure gauge. The S&P 

price varies according to the refrigerant content and the brand name. For this reason, people 

prefer to buy the charging kit once and then re-use it with S&P cans. It has to be noticed that 

the S&Ps are dominant (nearly 90% of the market, as assessed by several dealers) for two 

reasons: the more knowledgeable DIYers buy S&Ps due to the easiness of use; less 

knowledgeable, but price-oriented DIYers are also choosing S&Ps. Users prefer to buy S&P 

cans since they are cheaper than valve-equipped ones and they can re-use the charging kit with 

others S&P cans. 
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4.2.3 Tests and results 

The aim of this section is to evaluate the can tightness, before and after partial use, in order to 

verify if the can is tight enough to keep the remaining refrigerant in the can for a later use. 

The CEP has developed a method for determining the 

annual leak flow rate for MVAC components using 

infrared spectro-photometry [ACE05]. This method of 

testing is consistent with European regulation 706 / 

2007 [EU706]. The leak flow rate of a can is 

measured in an accumulation volume (see Photo 

4.16) by an infrared spectrophotometer. The raise of 

R-134a concentration is measured in the accumulation 

volume and translated into annual mass leak flow rate.

Photo 4.16 Accumulation volume 

where refrigerant annual leak is 

measured 

Before leak tests, the infrared gas analyzer is calibrated using three different refrigerant 

concentrations: 0, 100, and 450 ppm. The cell volume is calculated using a calibrated leak (see 

Figure 4.6). The LFR measurement relative uncertainty is about 6%. 

Cell volume calibration

Leak@21 °C = 47,8 g/yr 

0

20

40

60

80

100

120

140

160

180

200

0.0 0.3 0.5 0.8 1.0 1.3 1.5

Time (hr)

HFC-134a concentration (ppm)

 

Figure 4.6 Refrigerant concentration raise using a calibrated leak. 

 

As shown in Photo 4.16, the can is installed inside a hermetical volume where ambient pressure 

and temperature are controlled. Measurement starts when the preset temperature is reached. 

The annual leak flow rate is calculated using only the linear evolution of the refrigerant 

concentration. 

The measurement accuracy is better then 0.1 g/yr. 

As shown in Table 4.3, tests have been performed on S&Ps as well as on valve-equipped cans. 

The leak flow rates are determined before and after the use of cans. An S&P type can is 

considered new when the can tap of the charging kit is not screwed on it. A valve-equipped type 

can is considered new when it is intact as purchased. 
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Table 4.3 Small can leak test results. 

Net Weight [g] Type CEP Reference new used

°C °C

30 35 40 30 35 40 Charging Kit

Ezchill 510 V C1-01 3.17 3.88 5.28 3.41 4.05 4.79 F1-01

Ezchill 396 S&P C1-03 0.11 0.19 0.32 0.19 0.28 0.55 F1-02

Ezchill 510 V C1-02 0.83 1.24 1.95 0.86 1.24 1.65 F1-01

Ezcharge 396 V C1-04 0.62 1.03 1.73 0.55 0.86 1.51 F1-01

Ezchill 396 S&P C1-05 0.37 0.60 1.05 441 526 714 F1-09

Ezchill 397 V C1-06 0.97 1.59 2.27 0.70 2.08 3.34 F1-01

Ezchill 398 V C1-07 0.66 1.09 1.64 0.75 1.14 1.84 F1-01

Artic 396 S&P C1-08 0.39 0.62 0.97 1.52 2.23 2.60 F1-12

Artic 398 S&P C1-10 0.41 0.62 1.09 3.09 4.48 5.86 F1-11

High Mileage 368 S&P C1-13 0.33 0.49 0.77 0.41 0.62 1.06 F1-04

Johnsen's 340 S&P C3-01 0.02 0.04 0.03 139 298 604 F1-13

Johnsen's 340 S&P C3-02 0.004 0.005 0.01 37.0 50.1 67.8 F1-07

Johnsen's 340 S&P C3-03 0.004 0.008 0.01 0.02 0.03 0.05 F1-05

Sub-zero 538 S&P C4-01 0.04 0.05 0.08 0.04 0.05 0.08 F4-02

Sub-zero 538 S&P C4-02 0.05 0.07 0.11 0.06 0.11 0.19 F1-03

Leak Flow Rate [g/yr]

Technical Chemial Co,

Interdynamics

EF Products

Brand name

Small Can

Leak tests on V-type small cans 

For the valve-equipped cans (V-type), emissions are always slightly higher compared to S&Ps 

and in one case significantly higher (3.2 g/yr at 30°C). Values measured before and after can 

usage are of the same order of magnitude. 

All cans are brand new and when the tests are made before use, the test is labeled Brand New 

(BN). Five of the V-type small cans have been tested. These cans are all manufactured by 

Interdynamics. Since the self-closing valve is installed on the can, the charging kit does not 

contribute to refrigerant emissions before and after a partial use. 

Refrigerant emissions for new valve equipped cans are presented in Figure 4.7. As the leak flow 

rate and the saturation pressure are related in a quadratic relation, it is obvious that the leak flow

rate increases with temperature. Refrigerant emissions from the C1-01 can are three times 

higher than the other valve-equipped cans and lower than 6 g/yr. 

The second series of tests performed after the first use of the five V-type small cans were 

labeled After Use (AU). As shown in Photo 4.13, the actuator only pushes the stem downward 

and, when released, a spring pushes the stem and closes the container. This means that 

changes on emissions after use could only be related to the rubber seal that moves with the 

stem. Figure 4.8 shows the variation of the leak flow rate after the first use is never higher than 

1 g/yr and, for the C1-01 can, it is 0.5 g/yr lower than a new can. 

 

Leak flow rate (LFR) for new valve-equipped cans

0

1

2

3

4

5

6

LFR (g/yr) 30 °C 3.17 0.83 0.62 0.97 0.66

40 °C 3.88 1.24 1.03 1.59 1.09

50 °C 5.28 1.95 1.73 2.27 1.64

C1-01 C1-02 C1-04 C1-06 C1-07

Delta leak flow rate (LFR) after a partial use

-0.5

0.0

0.5

1.0

1.5

LFR (g/yr)

30 °C 0.24 0.03 -0.07 -0.27 0.09

40 °C 0.17 0.00 -0.17 0.49 0.05

50 °C -0.49 -0.30 -0.22 1.07 0.20

C1-01 C1-02 C1-04 C1-06 C1-07

Figure 4.7 Leak test results of new V-type cans 

(BN). 

Figure 4.8 Leak test results of V-type cans (AU). 
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Leak tests on type S&P small cans 

Five brand new S&P small cans have been tested. The leak test results for BN S&P small cans 

illustrates an important difference among the three different manufacturers that have been tested 

(see Figure 4.9). S&P small cans from manufacturer C1, are significantly more emissive than 

the C4 and C3 ones. For the same container pressure and type, we found refrigerant emissions 

from C1 cans 100 times higher than that of the C3 and C4 ones. 

Leak flow rate (LFR) for new S&P cans

0.0

0.2

0.4

0.6

0.8

1.0

1.2

LFR (g/yr)

30 °C 0.11 0.37 0.39 0.41 0.33 0.02 0.004 0.004 0.04 0.05

40 °C 0.19 0.60 0.62 0.62 0.49 0.04 0.005 0.008 0.05 0.07

50 °C 0.32 1.05 0.97 1.09 0.77 0.03 0.01 0.01 0.08 0.11

C1-03 C1-05 C1-08 C1-10 C1-13 C3-01 C3-02 C3-03 C4-01 C4-02

Figure 4.9 Leak flow rate test results of S&P cans (BN). 

These five S&P cans have been perforated for the first use and re-tested to evaluate the valve 

technology impact on the refrigerant emissions (see Table 4.2). These test results are 

presented in Figures 4.10 and 4.11. 

From the test results, it can be concluded that the push button charging kit technology is much 

more emissive than the shut-off valve. The lowest leak flow rate value obtained for the push 

button valve is about 1 g/yr and the highest one is about 700 g/yr, which proves the leak prone 

behavior of this technology. 

The leak flow rates of S&P cans, after use, depend on the type of charging kit used. The leak 

flow rate of the F1-02 charging kit is quasi similar to the one of a new S&P can. In contrast, the 

F1-13 charging kit presents very high LFR (139 g/yr at 30°C) as well as F1-09, with annual LFR 

of 441 g/yr. F1-07 is neither satisfactory with 37 g/yr at 30°C. Of course, all charging kits where 

the refrigerant release is higher than 3 g/yr will quickly lead to an empty can. 

Delta Leak flow rate (LFR) due to push button charging kit for S&P 

cans

0

100

200

300

400

500

600

700

800

LFR (g/yr)

30 °C 440.63 1.13 2.68 139.38 37.00

40 °C 525.20 1.61 3.86 298.16 50.10

50 °C 712.45 1.63 4.77 604.17 67.80

F1-09 F1-12 F1-11 F1-13 F1-07

Delta Leak flow rate (LFR) due to shut-off valve charging kit in S&P 

cans

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

LFR (g/yr)

30 °C 0.08 0.08 0.02 0.00 0.01

40 °C 0.09 0.13 0.02 0.00 0.04

50 °C 0.23 0.29 0.04 0.00 0.08

F1-02 F1-04 F1-05 F4-02 F1-03

Figure 4.10 Test result of the push button 

charging valve (AU). 

Figure 4.11 Test result of the shut-off charging 

valve (AU). 
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It can be concluded that some charging kits cannot be used on S&P cans after a partial charge, 

leading to a complete loss of the remaining refrigerant. Moreover, when using F1-13 charging 

kits during operation the CEP technician noticed significant emissions. 

When using the charging kit F1-09 at 30°C, the annual leak flow rate exceeds 400 g/yr , meaning 

that the refrigerant container will be empty in a few days. If a user chooses to use a shut-off 

valve and close it after the re-charging process, the increase in refrigerant losses could be 

neglected. 

The shut-off valve technology slightly impacts refrigerant emissions and, for the charging kit F4-

02, has no impact at all. The high performance of the shut-off valve is related not only to the use 

of just two seals, but also to the applied load in both seals. One of them is metal-to-metal (see 

Photo 4.12). 

4.2.4 Conclusions 

Based on the 90 leak tests presented above, refrigerant emissions from small cans before and 

after a partial use could be significant and depend strongly on the container and charging kit 

technology. 

Two different small can technologies have been tested: the V-type and the S&P type. As 

expected, S&P small cans before use show lower emissions compared to V-type small cans. 

Particularly, the S&P coming from the brand name C3 shows the lowest emission level, which is 

nearly nil (see Figures 4.7 and 4.9). This means that, when stored in the sales store, the S&P 

type small cans leak less than the V-type ones. 

The charging kits are adapted to the container type. For valve-equipped cans, the charging kit 

does not modify refrigerant emissions. Therefore, they present almost the same emission level 

after a partial use (see Figure 4.8). 

Two different charging valves have been tested for S&P type cans. The push button type has 

highly irregular emission behavior and an increase of 712 g/yr has been measured at 50°C (see 

Figure 4.10). The shut-off valve has been tested in the same conditions and presents emissions 

lower than 0.3 g/yr (see Figure 4.11). It has to be noticed that the S&P cans with a push-button 

charging kit and the valve-equipped cans have a self-closing system that prevents the user from 

emptying the container in a few seconds. 

In order to reduce refrigerant emissions before and after the re-charging process, appropriate 

cans and charging kits have to be chosen. These test results suggest the use of S&P cans with 

a shut-off valve charging kit will minimize HFC-134a emissions. 
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4.3 Sensitivity of Different Leak Search Methods 

4.3.1 Introduction 

In order to determine the effectiveness of the leak search methods, a comparative study of leak 

sensitivity to: dye, electronic leak detectors, and the soap bubble method was carried out, using 

the infrared spectroscope to measure exactly the LFR that can be detected by each method. 

Five fittings with the same 

design and different LFRs have 

been chosen (see Photo 4.17). 

They are composed of two 

flanges and one o-ring seal, and 

put together with a screw. 

Photo 4.17 Fittings technology used for this comparative study. 

4.3.2 Test procedure 

First, each fitting has been put under pressure with HFC-134a and installed inside an 

accumulation volume to be leak tested using an infrared spectrophotometer (IS). Refrigerant 

pressure is set to 770 kPa and the fitting temperature to 35°C, superheated to 5°C to avoid 

refrigerant condensation inside the component. This leak test is the same as the one described 

for the small can leak tests. This first test is followed by a leak search using an Electronic Leak 

Detector (ELD) and a Soap Bubbles (SB) test. 

The ELD leak detection is achieved by placing the sniffer as close as possible of the component 

and then moving slowly all around the flanges junction. If the leak detector audible alarm 

intensifies, then the leak is considered as detected. Before the leak search, the ELD is checked 

with a calibrated leak of 6 g/yr (see Photo 4.18). 

Photo 4.18 Calibrated leak for checking the ELD. Photo 4.19 Leak detection with Electronic Leak 

Detector. 

The SB leak detection is achieved by spraying the flanges junction with a soap solution. If the 

formation of bubbles is visible to the naked eye, then the leak is considered detected. 
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Photo 4.20 Leak detection with DYE Photo 4.21 Leak detection with Soap Bubble 

(1200 g/yr). 

The refrigerant LFR measured for Samples 4 to 6 have been performed before the dye 

visualization. 

Second, without disassembling the flanges, fittings have been charged with refrigerant 

HFC-134a, PAG lubricating oil, and dye. The refrigerant pressure is set to 770 kPa and the 

fitting temperature to 35°C. Then, they have been observed with a fluorescent light to determine 

the time taken by the refrigerant, oil, and dye to go through the leaky seal (see Photo 4.19). 

Once the test has led to positive detection, the refrigerant LFR is measured with the infrared 

spectrophotometer. Third, the ELD and the SB techniques are also tested (see Photos 4.20 and 

4.21). 

4.3.3 Leak test results and conclusions 

When comparing Tables 4.4 and 4.5, the fittings being in the same conditions, the lubrication 

effect is very significant especially for high LFRs. For example, for fitting no. 1, the lubrication of 

the fitting results in reducing the LFR from 662,000 g/yr to 14.7 g/yr, and for Sample no. 2 from 

1,490 to 120. This effect is systematic even if no general law can be derived from those tests. 

Lubrication of all fittings leads to significant improvement of leak tightness. 

For dry contact, only ELD and SB can be used because dye is diluted in the oil. As it can be 

seen in Table 4.4, the practical limit of detection has been 7.2 g/yr for both ELD and SB. 

Table 4.4 LFRs of fittings with dry contact. 

1

st leak test - Dry contact 

 Test method 

Sample IS [g/yr] ELD SB 

No.1 662,000 Detected Detected 

No.2 1,490 Detected Detected 

No.3 515 Detected Detected 

No.6 300 Detected Detected 

No.4 7.2 Not detected Not detected 

No.5 0.28 Not detected Not detected 

For the second series of tests with lubricated joints, strangely enough the threshold detection 

has been different and even a LFR of 14.7 g/yr has not been detected either by ELD or SB but 

has been detected by dye. 
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When comparing Samples 1, 2, and 3, it can be deduced that the lower the LFR, the longer the 

time the dye has to go through the leaky fitting. Sample 3 seems to indicate that a leak as low 

as 5.7 g/yr can be detected by dye only after 11 hours, this leak was not detected either by ELB 

or SB. 

Table 4.5 LFRs of fittings with lubricated contact.

2

nd leak test - Lubricated contact 

 Test method 

Sample IS [g/yr] ELD SB DYE [hr] 

No.1 14.7 Not detected Not detected 3 

No.2 120 Detected Detected** 0.8 

No.3 5.7 Not detected Not detected 11 

No.6 0.7 Not detected Not detected *** 

No.4 0.05 Not detected Not detected * 

No.5 0.05 Not detected Not detected * 

*No evidence of DYE after 21 days of test 

** Very small bubbles 

***No evidence of DYE after 15 days of test 

After a 21-day test, no evidence of dye has been noticed for Samples 4 and 5. 

For Sample 2 (14.7 g/yr with a lubricated contact), the SB method has generated very small 

bubbles, which are very difficult to visualize. 

It has to be noticed that in ELD and SB leak test methods, the leak search strongly depends on 

the leaky component accessibility. If fittings are not fully accessible, the leak visualization or 

location can be very hard to find. For the compressor shaft seal, the refrigerating system most 

leaky seal, detection using ELD and SB methods is impossible because the clutch assembly 

hides the shaft seal. 

In conclusion, adding dye to the oil seems to be a simple and efficient way to detect leaks in the 

very busy environment under the vehicle hood. Those first tests do not indicate a significant 

advantage of usual methods (ELD or SB) compared to the use of dye. 

The detailed fitting emissions are presented in Appendix A. 
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Appendix A: detailed fitting emissions 

Fitting No.1 : Dry contact Fitting No.1 : Lubricated contact 

Fitting No.2 : Dry contact Fitting No.2 : Lubricated contact 

Fitting No.3 : Dry contact Fitting No.3 : Lubricated contact 

Fitting No.4 : Dry contact Fitting No.4 : Lubricated contact 
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Fitting No.5 : Dry contact Fitting No.5 : Lubricated contact 

Fitting No.6_Dry contact

P = 770 kPa; T = 35 °C

LFR = 300 g/yr

0

25

50

75

100

125

150

0,0 0,1 0,2 0,3 0,4 0,5

Time (hr)

Q(moleE-6)

Fitting No.6_DYE+Oil

P = 770 kPa; T = 35 °C

LFR = 0,7 g/yr

0

2

4

6

8

10

0 2 4 6 8 10 12 14

Time (hr)

Q(moleE-6)

Fitting No.6 : Dry contact Fitting No.6 : Lubricated contact 

5. Evaluation of the sales of HFC-134a disposable cans in California 

Two sources are available to evaluate the number of small cans sold in California. Based on the 

2006 CARB consumer project survey, the number of HFC-134a small cans sold in California is 

close to 2 million cans per year equivalent to 0.85 MMT CO2 equivalent per year. This data has 

been presented by CARB at the Scottsdale SAE Conference 2008 [ZHA08]. 

In 2005, E. Hoffpauir of MACS 

presented the refrigerant sales of 

HFC-134a for servicing and for new 

vehicles, as shown in Figure 5.1. So if 

California represents 10% of the U.S. 

small can sales (which is a typical 

assumption), the equivalent CO2 is 

higher, in the range of 1.3 MMT CO2

equivalent. In any case, the order of 

magnitude of direct emissions is in the 

range of 0.33 MMT CO2 equivalent per 

year due to emissions during servicing 

by DIYers. 

Figure 5.1 HFC refrigerant sales for MAC systems - 

2003 [HOF05]. 
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6. Summary, conclusions, and recommendations 

The primary purpose of this project was to provide data for the regulatory development of a 

discrete early action under AB 32, the California Global Warming Solutions Act of 2006. The 

purpose of the regulatory measure was to reduce the emissions of high-GWP refrigerants during 

the re-charging of MVACs by DIY individuals. CEP staff also performed a field study of MVAC 

servicing by professional technicians in order to evaluate the procedures followed in professional 

servicing and repair. Additional data was generated which may be helpful in the development of 

other proposed regulations concerned with the emission reduction of high-GWP refrigerants 

from MVAC systems. 

The CEP staff performed two field studies including measurements of refrigerant emissions from 

the DIY re-charging of MVAC systems in the field. The first field study focused on analyzing 

approximately 50 Do-It-Yourself (DIY) recharges on auto A/C units using from one or more small 

containers of automotive refrigerant. Through the measurements of refrigerant masses in the 

MVAC system and the container, the CEP staff calculated refrigerant emissions and their 

components during the DIY re-charging procedure. The second field study was a qualitative 

study of the diagnostic and servicing practices of professional A/C servicing facilities when an 

MVAC system is significantly undercharged. 

In addition, laboratory tests were conducted to demonstrate: (1) how much refrigerant would be 

lost before the cooling performance of a selected MVAC began to deteriorate significantly, (2) a 

comparison of the sensitivity of different methods of leak detection, (3) the typical leak flow rates 

from “small cans” and their charging apparatus, and (4) the typical leak flow rate of the MVAC 

systems in the five most popular cars in California. 

Refrigerant Emissions from DIY MVAC Re-Charging

Based on the field testing with DIY 

volunteers, two-thirds of the “small 

container” refrigerant is charged into the 

MAC system while 1/3 is emitted to the 

atmosphere. See the figure on the right. 

Almost 80 percent of the volunteers chose 

the S&P type cans because they already 

have the charging assembly and it is 

cheaper. It is also important to note that a 

small number of DIYers was responsible 

for the majority of the emissions. 43 

percent of the operations resulted in 78 

percent of the emissions indicating the 

need for proper training. 

Leak flow rate (LFR) for new valve-equipped cans

0

1

2

3

4

5

6

LFR (g/yr) 30 °C 3.17 0.83 0.62 0.97 0.66

40 °C 3.88 1.24 1.03 1.59 1.09

50 °C 5.28 1.95 1.73 2.27 1.64

C1-01 C1-02 C1-04 C1-06 C1-07

Figure a – Components of a DIY Refrigerant Charge. 

The main drawbacks associated with non-professional servicing are: 

(1) DIYers not knowing the amount of refrigerant remaining in the system or the manufacturers’ 

specified charge, (2) MVAC system leak search and repair are not conducted, (3) DIYers not 

recovering the refrigerant from the MVAC system prior to re-charging, and (4) incorrect 

instructions on the container labels. 

Recommendations: For the DIY practice to be effective the use of the pressure gauge in recharging the MVAC should be discontinued because it is not a proper indicator of the level of the 

system refrigerant charge. In addition, the following instructions need to be included on the 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -73 -

container label: (1) the engine must be running, (2) set the A/C system to maximum cooling with 

the fan on high, (3) an explanation of the can shaking procedure to achieve a properly charged 

system, and (4) an explanation for determining when a container is empty. This last instruction 

would include minimal liquid movement from inside the shaken container and a temperature rise 

of the container.

Emissions from Small Containers 

There are two types of small containers available on the market: the screw-and-perforate (S&P) 

and the valve-equipped (V). According to the laboratory leakage measurements, new S&P type 

containers have an insignificant advantage over the V type containers prior to their use in recharging a MVAC. 

After use, the V type containers showed little difference in leak rate when compared with the 

new V type containers prior to use. Leak rate measurements were also carried out on S&P type 

cans with different charging assemblies installed. In two of the five cases, the kit equipped with 

the “push-button type” assembly resulted in emission increases of greater than 100 g/yr after 

use. In addition, this type of charging assembly released refrigerant during the re-charging 

process. In comparison, all charging assemblies with the shut-off valve increased refrigerant 

emissions by less than 0.3 g/yr after opening and closing the valves. 

Recommendation: Prior to use, the leak rates from both V type and S&P type containers are 

very low. However, the design of the charging valve and hose assembly and its interface with 

the S&P type container may have a significant effect on the emissions from the small containers 

of automotive refrigerant. The “push-button” type charging kits for the S&P type cans should 

either be banned or re-designed to reduce refrigerant emissions during and after usage. 

Professional Servicing 

CEP staff conducted a field survey of professional A/C shops by taking in a vehicle with an 

intentionally under-charged MVAC to observe the procedures that the technicians followed and 

their diagnosis of the system performance. 

The first check ups included: (1) verification 

of the air temperature coming out of the vents 

in the cabin, (2) actuation of the compressor 

clutch, (3) measurement of the low and high 

pressures with the A/C on, (4) identification of 

the refrigerant in the system using an 

electronic analyzer, and (5) verification of the 

pressure inside the A/C loop by pressing the 

HP or LP Schrader valves. The figure to the 

right shows the frequency of the different 

types of checks done by the professional 

technicians. Note that DIYers as well as 

professionals check the ventilation air 

temperature while the other checks require 

the expertise and equipment of a professional 

technician. 

Preliminary AC check (50 cases)

0

5

10

15

20

25

30

35

40

45

air

temperature

Comp clutch HP LP Refrigerant

analysis

Press

shrader

Number of cases

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Sample percentage

Figure b: Method of diagnosis of the sample of 

professionals 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -74 -

Followed by the system checks, the technicians diagnosed the system problems and 

recommended a course of action which consisted primarily of re-charging the MVAC system with 

refrigerant in over 90 percent of the cases. In almost 70 percent of the cases, the technician 

recommended that a leak search be carried out although this was only done in approximately 75 

percent of these cases. There is some degree of variation in the check-up, diagnosis and 

recommendations performed by the technicians. 

Professional Servicing with Recovery and Recharge Machines 

About two-thirds of the professionals used automated recovery and recharge machines. This 

equipment is essential for limiting refrigerant emissions during servicing, provided the recovery is 

performed down to an absolute pressure of 4 psia. It was also observed that few professionals 

verify the refrigerant charge specified by the car manufacturer. 

Different types of couplings are used in connecting the recovery and recharge machines to the 

MVAC systems. The usage of certain types of these couplings results in lower emissions of 

refrigerant. Standard testing should be performed on all couplings with the results published in 

order to promote the use of the ones with lower emissions. 

Many fully automated recovery machines evacuate after recovery. A significant amount of 

refrigerant may be released during the evacuation process because if recovery stops at an 

absolute pressure around 14 psia. These emissions could be reduced by continuing recovery 

until a lower pressure is reached. 

Recommendations: All professionals should use recovery and recharge machines in servicing 

MVAC systems. The professional technician should make a systematic leak search before 

refrigerant recovery when the saturating pressure is measured in the MAC system. When 

performing an A/C service, the technician should ensure that the manufacturers’ specified 

refrigerant charge is used and, upon completion of the service, a tag or sticker should be placed 

under the hood indicating the date of service. The low-pressure threshold for refrigerant 

recovery should be set at 4 psia so that more refrigerant is recovered from the MVAC system. 

Professional Leak Search 

Twentysix technicians performed the leak check using the following methods: 

(1) controlling the pressure rise after evacuation, (2) detection of UV-sensitive dye in the 

refrigerant, (3) using an electronic leak detector, and (4) the inspection for soap bubbles on a 

pressurized MVAC system. The majority of the technicians used the detection of UV dye with 

the electronic leak detector being used to a lesser degree. 

The UV dye method is the only one that can be performed by the non-professional, because the 

other techniques require a professional’s expertise and equipment. It should be noted that none 

of the technicians who participated in the study were able to detect a refrigerant leak even 

though CEP staff was aware of a very small leak at the expansion valve. The observations on 

professional leak detection concerning the necessary time lag between charging the dye and 

making a possible diagnosis of a leak is confirmed by laboratory tests which are described 

below. 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -75 -

The comparison of three detection methods at the 

CEP laboratory shows that the usage of a fluorescent 

lamp with UV dye is comparable or superior to either 

an electronic leak detector or the use of a soap 

solution on a pressurized MVAC system with an 

inspection for bubbles. The UV dye method has the 

capability of detecting a leak flow rate as low as 

approximately 6 g/yr after 11 hours. 

Recommendation: A UV dye should be included in 

the refrigerant when the MVAC is charged during 

vehicle manufacture. This would give service 

technicians a simple means of identifying leaks. 

Figure c: Visualization of leak by UV 

dye. 

Costs of Professional and Non-Professional Servicing 

From the survey of professional shops, the cost for diagnosing a MVAC problem ranges from no 

charge to $20. For a professional diagnosis and re-charging with a recovery and re-charge 

machine, the cost ranges from approximately $50 to a little over $200. This may or may not 

include a leak inspection depending on the shop. If the professional shop performs a diagnosis 

and a recharge using small containers or a bottle of refrigerant, then the cost is under $100 

according the shops that were checked. It should be noted that only a small number of 

professionals gave a diagnosis or incorrect recommendations concerning the servicing/repair of 

the MVAC. For non-professional servicing/re-charge, the cost of the refrigerant container and 

the charging assembly may range from $15 to $40 depending on the circumstances. The nonprofessional servicing may provide a major cost savings for the consumer if the only problem is 

a low-refrigerant charge. 

However, it should be remembered that professional servicing does provide an added value over 

non-professional servicing. Professional technicians specialize in servicing/repairing MVAC 

systems and possess the expertise and equipment to effectively perform their duties. The 

potential added values include: (1) correct diagnosis of failure, (2) effective leak search, (3) use 

of a recovery & recharge machine, and (4) capability of repair. 

Leak Rates from New MVAC Systems 

The annual leak flow rates (LFRs) of MAC systems of the five most sold cars in California have 

been measured according to the methodology defined in the EU regulation 706/2007. The initial 

annual leak flow rates of those five MAC systems are of the same order of magnitude as those 

measured on European and Japanese cars. The average annual LFR of new systems is in the 

range of 10 g/yr ±4. MVAC systems with double evaporator systems may have higher leak 

rates because of the extra connections, although two of the tested systems did have double 

evaporators. 

Additional testing was conducted on one of the MAC systems. The system was mounted on a 

test bench, running continuously over 7 hours with a fixed leak rate of 1.5 g/min. Cooling 

performance data indicated that about 50% of the refrigerant charge has to be lost before the 

system ceases to perform adequately. 

Recommendations: The refrigeration circuit of MAC systems should not require any servicing 

during the first 7 years because “regular” leaks are low unless there is some sort of catastrophic 

failure in the system. It is recommended that additional research work be conducted in order to 
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -76 -

analyze the wear and degradation of compressor shaft seals over time. This would lead to a 

greater understanding of why and when MAC systems become significantly more emissive.

An Alternative Approach for Do-It-Yourself MVAC Servicing 

In re-charging a MVAC with a small container, the DIYer 

connects the charging hose assembly to the small can 

and the low-pressure service valve and shakes the can 

while charging the system until the can feels empty. 

In using an automated R&R machine, an individual 

would connect the blue hose to the low-pressure service 

valve, connect the red hose to high-pressure service 

valve, push the button, and return approximately half an 

hour later after the completion of recovery and recharge. 

If you compare these two procedures, the use of an 

automated machine is simpler. Figure d: Automated Recovery and 

recharge machine. 

It would be possible to allow DIYers to continue recharging their MVAC systems without using 

the small containers of automotive refrigerant. Instead of buying small cans, DIYers could rent 

the use of a recovery & recharge machine at an auto-parts retailer. This approach would be 

similar to an individual inflating the tires on his automobile. A person does not buy a compressor 

to do this operation but typically goes to a gasoline service station. In addition, a DIYer could 

perform a leak check on his MVAC by renting a UV lamp from the auto-parts retailer. This would 

be a relatively simple process If UV dye is included with the refrigerant charge at the factory 

when the vehicle is being manufactured. The dye could also be injected by either a professional 

or a DIYer using a small can with dye. 

Recommendations: Instead of using small containers to perform non-professional servicing, the 

DIYer should use a recovery & recharge machine that would be rented at auto-part stores. DIY 

individuals should perform leak checks on their systems. This would be feasible by charging 

refrigerant with UV dye at the factory, and auto-parts stores offering UV lamps for rent. In the 

interim, dye can be charged either by professionals or non-professionals.
Evaluation of the Potential Impact of Emissions of HFC-134a From Non Professional Servicing of Motor Vehicle Air 

Conditioning Systems – Final Report – December 2008 -77 -

References 

[ACE05] Clodic, Denis, Yu, Yingzhong. Research study on the definition of the implementation 

of a method of measurement of annual leak flow rates (LFRs) of MAC systems. 

Report pour ACEA. January 2006. 

[CLO06] D. Clodic, Y. Yu. 2005. Research study on the definition of the implementation of a 

method of measurement of annual leak flow rates (LFRs) of MAC systems. Report for 

ACEA. January 2006. 

[EUD06] Directive 2006/40/CE du Parlement européen et du Conseil du 17 mai 2006 

concernant les émissions provenant des systèmes de climatisation des véhicules à 

moteur et modifiant la directive 70/156/CE du Conseil. 

[EUR07] Règlement (CE) n° 706/2007 de la Commission du 21 juin 2007 établissant 

conformément à la directive 2006/40/CE du Parlement européen et du Conseil les 

dispositions administratives relatives à la réception CE des véhicules ainsi qu'un 

essai harmonisé pour mesurer les fuites de certains systèmes de climatisation. 

[EU07] Commission regulation (EC) No 706/2007 of June 2007 laying down, pursuant to 

Directive 2006/40/EC of the European Parliament and of the Council, administrative 

provisions for the EC-type-approval of vehicles, and a harmonized test for measuring 

leakages from certain air conditioning systems. 

[HOF05] Elvis Hoffpauir. 2005. Reducing Refrigerant Emissions at Service and Vehicle End of 

Life. MAC Summit 2005. Sacramento, California.

[ZHA08] Tao Zhan et al. 2008. Greenhouse Gas Emissions and Abatement Opportunities in 

Do-it-Yourself Recharging of Leaky Motor Vehicle Air Conditioning Systems in 

California. SAE Congress, Scottsdale, Arizona. 

Abbreviations and acronyms 

Abbreviations 

AC Air conditioning 

DIYer Do-it-yourselfer 

ELD Electronic leak detector 

HFC Hydrofluorocarbons 

HP High pressure 

IS Infrared spectrophotometer 

LFR Leak flow rate 

LP Low pressure 

MAC Mobile air conditioning 

MACS Mobile air-conditioning system 

MVAC Motor vehicle air conditioning 

OT Orifice tube 

S&P Screwed & perforated 

SB Soap and bubbles 

SC Small can 

SCU Small can user 

SUV Sport utility vehicle 

TxV Thermostatic expansion valve 

UV Ultraviolet 

Acronyms 

CARB Californian Air Resources Board 

CEP Center for Energy and Processes