Test Procedure for Leaks from 

Small Containers of Automotive Refrigerant 

TP-503 

Adoption Date: July 20, 2009 

As Last Amended: January 5, 2010

NOTE: This document, approved by the Air Resources Board at its January 

22, 2009 hearing for incorporation by reference in California Code of 

Regulations (CCR), title 17, sections 95360 through 95370, was originally 

shown without underline as permitted by California Code of Regulations, 

title 1, section 8. The modifications are indicated in underline to indicate 

additions and in strikeout to indicate deletions. 
TP503, Page i 

TABLE OF CONTENTS 

1. APPLICABILITY ....................................................................................................................... 1

2. PRINCIPLE AND SUMMARY OF TEST PROCEDURE ..................................................... 1

3. BIASES AND INTERFERENCES ............................................................................................ 2

4. SENSITIVITY AND RANGE .................................................................................................... 3

5. EQUIPMENT .............................................................................................................................. 3

6. CALIBRATION PROCEDURES.............................................................................................. 3

7. CAN PREPARATION................................................................................................................ 4

8. CAN WEIGHING ....................................................................................................................... 4

9. CALCULATIONS....................................................................................................................... 6

10. RECORDING AND REPORTING DATA............................................................................... 7

11. QUALITY ASSURANCE / QUALITY CONTROL................................................................ 7

ATTACHMENT A............................................................................................................................. 11
TP503, Page 1 

California Environmental Protection Agency 

Air Resources Board

TP-503 

Test Procedure for Leaks from Small Containers of Automotive 

Refrigerant 

The definitions in Section 95361 of Title 17, California Code of Regulations (CCR) 

apply to this test procedure. 

In these procedures, the term "ARB" refers to the California Air Resources Board, 

and the term "Executive Officer" refers to the ARB Executive Officer or his or her 

authorized representative. 

1. APPLICABILITY 

This test procedure is used by manufacturers of small containers of automotive 

refrigerant and ARB to determine the leakage rate of small containers of automotive 

refrigerant that are subject to the requirements of Title 17,CCR section 95360 et seq. 

Specifically, this test procedure will specify the equipment, procedures, and 

calculations to determine if a small container of automotive refrigerant complies with 

the leakage rate specified in section 2.1(B) of the Certification Procedures for Small 

Containers of Automotive Refrigerant, adopted [BARCU will insert] July 20, 2009, and 

last amended on [INSERT DATE OF AMENDMENT], 

 

Requirement to Comply with All Other Applicable Codes and Regulations 

Approval of a small container of automotive refrigerant by the Executive Officer does 

not exempt the container from compliance or with other applicable codes and 

regulations such as local, State or federal safety codes and regulations. 

Safety 

This test procedure involves the use of materials under pressure, and operations 

and should only be used by or under the supervision of those familiar and 

experienced in the use of such materials and operations. Appropriate safety 

precautions should be observed at all times while performing this test procedure. 

2. PRINCIPLE AND SUMMARY OF TEST PROCEDURE 
TP503, Page 2 

This procedure is used to determine the leakage rate of small containers of 

automotive refrigerant (small cans). Testing will involve subjecting both full and 

partially empty cans in both upright and inverted positions at two temperatures: 73 oF 

and 130 oF. 

Thirty cans are tested under each condition for a total of 240 cans tested. Cans are 

brought to temperature stability, weighed, then stored for 30 days under specified 

conditions of temperature, orientation, and state of fill, then re-weighed. Leakage 

rate (grams/year) is estimated by (weight loss in grams) *365 / (days duration). The 

leakage rate is then compared to a standard of 3 grams/year to determine if a given 

small can complies with the leakage rate specified in section 2.1(B) of the 

Certification Procedures for Small Containers of Automotive Refrigerant, adopted 

[BARCU will insert] July 20, 2009, and last amended on [INSERT DATE OF AMENDMENT], 

. 

3. BIASES AND INTERFERENCES 

3.1. Contaminants on the operator’s hands can affect the weight of the can and 

the ability of the can to absorb moisture. To avoid contamination of the 

can, the balance operator should wear gloves while handling the small 

cans. 

3.2. Weight determinations can be interfered with by moisture condensing on 

the can and by thermal currents generated by temperature differences 

between the can and the room temperature. The small cans cool during 

discharge and could cause condensation. For these reasons, cans must 

be equilibrated to balance room temperature for at least four hours before 

weighing. 

3.3. Variations in the temperature, pressure, and humidity of the ambient air will 

cause variations in the buoyancy of the small can. These variations 

should typically be less than 25 mg for a small can. If the can is not 

leaking at all, then the uncorrected weight changes will be within the range 

of 0 +/- 25 mg, which is about ten percent of the 247 mg loss expected 

after thirty days for a can leaking at 3 g/yr. In that case buoyancy 

corrections can be omitted. If the absolute value of the uncorrected 

weight change exceeds 25 mg, then all calculations must be made using 

weights corrected for buoyancy based on the temperature, pressure, and 

humidity of the weighing room. 

3.4. Some electronic balances are sensitive to the effects of small static 

charges. The small can should be placed directly on the balance pan, 

ensuring metal to metal contact. If the balance pan is not grounded, the 

can and balance pan should be statically discharged before weighing. 
TP503, Page 3 

4. SENSITIVITY AND RANGE 

The mass of a full can could range from roughly 50 to 1000 grams depending on the 

container capacity. A top loading balance, capable of a maximum weight 

measurement of not less than 1,000 grams and having a minimum readability of 

0.001 gram, reproducibility and linearity of ± 0.002 grams, must be used to perform 

mass measurements (examples: Sartorius LA1200S, Mettler XS1003S, etc). 

5. EQUIPMENT 

5.1. A top loading balance that meets the requirements of Section 4 above. 

5.2. A NIST traceable working standard mass for balance calibration. A NIST 

traceable working standard mass for a balance linearity check. A 

reference mass to serve as a “blank” can. 

5.3. A enclosure capable of controlling the internal air temperature from 73 o

F 

+/- 5 oF and an enclosure capable of controlling the internal air temperature 

to 130 o

F, +/- 5 oF. 

5.4. A temperature instrument capable of measuring the internal temperature of 

the temperature conditioning enclosures and the balance room with a 

sensitivity of +/- 2 oF. 

5.5. A barometric pressure instrument capable of measuring atmospheric 

pressure at the location of the balance to within +/- 0.02 inches of mercury. 

5.6. A relative humidity measuring instrument capable of measuring the relative 

humidity (RH) at the location of the balance with a sensitivity of +/-2% RH. 

5.7. A hose with appropriate fitting for dispensing refrigerant from the small can 

to a recovery machine. 

5.8. A refrigerant recovery machine to collect the discharged refrigerant from 

cans being tested.

6. CALIBRATION PROCEDURES 

Calibrations are applied to the balance and to the support equipment such as 

temperature, humidity, and pressure monitoring equipment. Procedures for 

calibration are not spelled out here. General calibration principals for the support 

equipment and the balance are described in Section 11, Quality Assurance / Quality 

Control. Detailed calibration procedures for measurement made using the balance 

are contained in Balance Protocol (BP–A1) “Balance Protocol for Gravimetric 

Determination of Sample Weights using a Precision Balance” adopted [BARCU will 

insert] July 20, 2009, and last amended on [INSERT DATE OF AMENDMENT],

which is incorporated by reference herein. 
TP503, Page 4 

7. CAN PREPARATION 

7.1. Receive a batch of 240 cans of one design to be tested. These may include 

several SKUs from different manufacturers if the container and valve 

combination are the same. 

7.2. Clean cans with Alkanox solution or equivalent and dry with lint free towel. 

7.3. Confirm that the sample ID sticker on the can matches the sample ID on 

the chain of custody forms. 

7.4. Select a reference mass similar to the weight of a full can. If multiple sets 

of similar sized cans are being tested, only one reference mass is needed; 

it can be used with all sets. Store the reference mass in the balance area.

7.5. Discharge the contents of one half of the cans (120 cans) into the 

refrigerant recovery machine using normal DIY dispensing procedures until 

each small can is approximately half full. 

7.6. Select a reference mass similar the weight the half full small can. If multiple 

sets of similar size cans are being tested, only one reference mass is 

needed; it can be used with all sets. Store the reference mass in the 

balance area.

8. CAN WEIGHING 

Weighing cans on the balance is done in accordance with Balance Protocol (BP-A1) 

adopted [BARCU will insert] July 20, 2009 and last amended on [INSERT DATE OF 

AMENDMENT], which is incorporated by reference herein. The Balance Protocol 

describes how to conduct weight determinations including appropriate calibration 

and QC data. This section, Can Weighing, describes the overall process, not the 

details of how to use the balance. 

Initial Weights 

8.1. Put on gloves. Check the cans for contamination. 

8.2. Place the 240 cans into a location where they can equilibrate to balance 

room temperature. Record the can test IDs and the equilibration start 

time on the Small Can Test Data Forms (Form TP–503–01) in sets of thirty, 

one form for each of the eight each test conditions. 

8.3. Let cans equilibrate for at least four hours. 

8.4. Weigh the set of 240 cans and the reference weights using the Balance 

Protocol (BP–A1) “Balance Protocol for Gravimetric Determination of 

Sample Weights using a Precision Balance” adopted [BARCU will insert]

July 20, 2009 and last amended on [INSERT DATE OF AMENDMENT], 

which is incorporated by reference herein, and log the results to the 
TP503, Page 5 

Balance Weighing Log Form (Form TP–503–02) attached to this test 

procedure. 

8.5. Transfer data from the Balance Weighing Log Form to the Small Can Test 

Data Forms in sets of 30, one set for each of the eight conditions to be 

tested. 

Thirty-Day Soak 

8.6. Place each set of 30 cans into the appropriate orientation and temperature 

for soaking:

 30 full cans – 73 o

F, upright 

 30 full cans – 73 o

F, inverted 

 30 full cans – 130 oF, upright 

 30 full cans – 130 o

F, inverted 

 30 half-full cans – 73 oF, upright 

 30 half-full cans – 73 o

F, inverted 

 30 half-full cans – 130 oF, upright 

 30 half-full cans – 130 o

F, inverted 

8.7. Soak the cans for 30 days undisturbed. 

Final Weighing 

8.8. Place the 240 cans into a location where they can equilibrate to balance 

room temperature. 

8.9. Let the cans equilibrate for at least four hours. 

8.10. Weigh the set of 240 cans, the reference weights, and any additional sets 

of cans using the Balance Protocol (BP–A1) “Balance Protocol for 

Gravimetric Determination of Sample Weights using a Precision Balance” 

adopted [BARCU will insert] July 20, 2009 and last amended on [INSERT 

DATE OF AMENDMENT], which is incorporated by reference herein. 

8.11. Transfer data from the Balance Weighing Log Form to the corresponding 

Small Can Test Data Forms.

Can Storage (only applicable to ARB) 

8.12. If the cans can pass the leak rate criteria, the cans may be recycled. 

(Return the cans to the place of purchase for recycling). 

8.13. If the cans do not pass the leak rate criteria, then mark the set with the 

message “Hold until released by Enforcement Division”. Transfer the entire 

set of cans to safe storage location. 
TP503, Page 6 

9. CALCULATIONS 

Corrections for Buoyancy 

The calculations in this section are described in terms of “weight.” Mass is a 

property of the can, whereas weight is a force due to the effects of buoyancy and 

gravity. Procedures for correcting the effect of buoyancy are given in Attachment A 

of this procedure. Ignoring buoyancy, i.e. using weight data uncorrected for 

buoyancy effects, is acceptable for a thirty day test if the absolute magnitude of the 

weight change is less than 25 mg. If the uncorrected weight change exceeds 25 mg 

for any can, then correct all can weights for buoyancy using the procedures in 

Attachment A before performing the calculations described below. 

Calculation of Leak Rate 

The emission rate in grams/day for each can is calculated by subtracting the final 

weight from the initial weight and then dividing the weight difference by the time 

difference measured in days to the nearest hour (nearest 1/24 of a day). The 

emission rate in g/day is multiplied by 365 to determine emission rate in grams/yr. 

If the annual emission rate for any can exceeds the entire can contents, then the 

annual emission rate for that can is adjusted to equal the entire can contents/year 

(e.g., about 350 g/yr for a 12 ounce can). The annual emission rate for the purpose 

of the test is calculated by averaging the 240 individual adjusted annual emission 

rates and rounding to 2 decimal places. The cans fail the test if the adjusted annual 

emission rate averaged over 240 cans is greater than 3.00 grams/yr. The 

calculations are described below. 

Loss rate for each can 

 Eidaily = (Wifinal – Wiinitial) / (Difinal – Diinitial), grams/day 

 Eiannual = 365* Eidailly grams/year 

 EIadjusted = Minimum of (Eiadjusted, Ci/year) grams/yr 

Where, 

 Ei = emission rate 

 Wifinal = weight of can i after soaking (grams) 

 Wiinitial = weight of can I before soaking (grams) 

 Difinal = date/time of final weight measurements (days) 

 Diinitial = date/time of initial weight measurements (days) 

 Ci = original factory mass of refrigerant in can i

Note Date/Times are measured in days. Microsoft Excel stores dates and times in 

days, and the calculations can be made directly in Excel. If calculations are made 

manually, calculate serial days to the nearest hour for each date and time as follows: 
TP503, Page 7 

 D = Julday + Hour/24 

Where, 

 Julday = serial day of the year: Jan 1 = 1, Jan 31 = 31, Feb 1 = 32, etc. 

 Hour = hour of day using 24-hour clock, 0 to 23 

Calculate the average loss rate for the 240 cans as follows: 

 Emean = [Sum(Eadjustedi), i=1 to 240 ] /240 

10. RECORDING AND REPORTING DATA 

During can weighing, record the can weights and date/times on the Balance 

Weighing Log Form. After each weighing session, transfer the measured weights 

and date/times from the Balance Weighing Log Form to the Small Can Test Data 

Form. 

At the end of the test, complete the calculations described in Section 9, Calculations, 

and record the results on the Small Can Test Data Forms. 

At the end of the test, transmit a copy of the Small Can Test Data Forms to the 

Project Engineer. 

11. QUALITY ASSURANCE / QUALITY CONTROL 

11.1. All temperature, pressure, and humidity instruments should be calibrated at 

least annually against NIST traceable laboratory standards. The main 

purpose of the NIST traceable calibration is to establish the absolute 

accuracy of the device. The instruments should also be checked 

periodically such as weekly, monthly, or quarterly against intermediate 

standards or against independent instruments. For example, a 

thermocouple can be checked weekly against a wall thermometer. A 

barometer or pressure gauge can be checked weekly by adjusting to sea 

level and comparing with local airport data. The main purpose of the 

frequent checks is to verify that the device has not failed in some way. 

This is especially important for electronic devices such as a digital 

thermometer, but even a liquid filled thermometer can develop a problem 

such as a bubble. 

11.2. The balance should be serviced and calibrated at least annually by an 

independent balance service company or agency using NIST traceable 

reference masses. Servicing verifies accuracy and linearity, and the 

maintenance performed helps ensure that a malfunction does not develop. 
TP503, Page 8 

11.3. The balance must also be calibrated and its linearity checked with working 

standards before and after each weighing session, or before and after each 

group of 24 cans if more than 24 cans are weighed in a session. 

Procedures for calibrating and using the balance, as well as recording 

balance data, are described in the accompanying balance weighing 

protocol. These procedures include zero checks, calibration checks, and 

reference mass checks. Procedures for calculating quality control data 

from those checks are described in the balance protocol. 

11.4. The small containers are cleaned then handled using gloves to prevent 

contamination. All equilibration and soaking must be done in a dust free 

area. 
TP503, Page 9 

Form TP–503–01: Small Can Test Data Form

 Enforcement Lot ID Full: Upright: T=73 F:

Half full: Inverted: T= 130 F:

Date: _______ Date: _______ Adjusted

Initial Initial Final Final Delta Delta Annual 

time weight Time Weight Days Weight Rate

Can ID (hour) (g) (hour) (g) (g) (g/yr)

_______ _______ _______ _______ _______ _______ _______ _______

_______ _______ _______ _______ _______ _______ _______ _______

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_______ _______ _______ _______ _______ _______ _______ _______

_______ _______ _______ _______ _______ _______ _______ _______

Number of Samples: _________ Average Loss Rate: _________

Technician: _________ Standard Deviation: _________

Comments:
TP503, Page 10 

Form TP–503–02: Balance Data Log Form 

QC Can Can Recorded

Rec # Date Time Proj. Prot. Tech. Code Type ID# grams Com

123456789

10111213141516171819202122232425
TP503, Page 11 

Attachment A 

Compensation of Weight Data for Buoyancy and Gravity Effects 

Gravity 

Variations in gravity are important only when weighing objects under different 

gravitational fields, i.e. at different locations or at different heights. Since the balance 

procedures calibrate the balance against a known mass (the calibration “weight”) at the 

same location where sample objects are weighed, there is no need to correct for 

location. Although both the sample and the calibration weight are used at the same 

location, there will be a difference in the height of the center of gravity of the sample 

object (small can) and the center of gravity of the reference mass (calibration weight). 

However, this difference in height is maintained during both the initial weights and final 

weights, affecting the initial and final weights by the same amount, and affecting the 

scale of the weight difference by only a few ppm. In any event, the magnitude of this 

correction is on the order of 0.3 ug per kg per mm of height difference. A difference on 

the order of 100 mm would thus yield a weight difference of about 0.03 mg, which is 

insignificant compared to our balance resolution which is 0.001 g or 1 mg. 

Based on the discussion above, no corrections for gravity are necessary when 

determining weight changes in small cans. 

Buoyancy 

Within a weighing session, the difference in density between the sample object and the 

calibration weight will cause the sample object weight value to differ from its mass value 

due to buoyancy. For a 1-liter object in air at 20oC and at 1 atm, the buoyant force is 

about 1.2 grams. The volume of a 1 kg object with a density of 8 g/cm3 (e.g. a 

calibration weight), is about 0.125 liters, and the buoyancy force is about 0.15 g. 

Variations in air density will affect both of these values in proportion. The net value 

being affected by variations in air density is thus on the order of 1.2 - 0.15 = 1.05 g. Air 

density can vary up or down by 2% or more due to variations in barometric pressure, 

temperature, and humidity. The buoyancy force will then vary up or down by 0.02 g, or 

20 mg. This is significant compared to the weight change expected after one week for 

a can leaking at 3 grams per year, which is 57 mg. 

Based on the discussion above, buoyancy corrections must be made. 

Variables measured or calculated: 

Vcan = volume of can (cm3

). Estimate to within 10% by measuring the can dimensions 

or by water displacement. Error in the can volume will cause an error in the 

absolute amount of the buoyancy force, but will have only a small effect on the 

change in buoyancy force from day to day. 
TP503, Page 12 

Wcan = nominal weight of a can (g), used to calculate the nominal density of the can 

ρcan = nominal density of a small can (g/cm3). The nominal values can be applied to 

corrections for all cans. It is not necessary to calculate a more exact density for 

each can. Calculate once for a full can and once for a half full can as follows: 

ρcan = Wcan / Vcan

T = Temperature in balance chamber (degrees Celsius) 

RH = Relative humidity in balance chamber (expressed a number between 0 and 100) 

Pbaro= Barometric pressure in balance chamber (millibar). Use actual pressure, NOT 

pressure adjusted to sea level. 

ρair = density of air in the balance chamber (g/cm3). Calculate using the following 

approximation 

ρair = 0.001*[0.348444*Pbaro – (RH / 100)*(0.252*T – 2.0582)] / ( T + 273.15) 

ρref = the reference density of the calibration weight (g/cm3

3

). Should be 8.0 g/cm3. 

Equation to correct for buoyancy 

 Wcorrected = Wreading * (1 - ρair / ρref ) / (1 - ρair / ρcan )