# Refrigerant exposure to service personnel or DIYers due to leakage of 12 oz charging cans or “small cans”



# Experiments Conducted at Honeywell’s Research Laboratory in Buffalo, NY USA

J a n u a r y 2 0 1 2Page 2 Section 1: INTRODUCTION: USE OF 12 OZ REFRIGERANT “SMALL” CANS IN VEHICLE CHARGING

Twelve ounce charging cans or “small cans” have been used by DIYers and small shops to charge R12 and R-134a automotive systems. These c onvenient cans can provi de improved cooling performance and operating efficiency for refrigerant sy stems that have lost si gnificant charge due to hose permeation, compressor shaft seal leakage, and fitting/joint leakage. A lthough latest generation components have significantly lowe r refrigerant loss rates than olde r components, there will be a loss in charge over the life of the vehicle. A sy stem that is low on char ge is not necessarily defective; it may be working with in its expected engineering desi gn parameters. Since early R-12 and R-134a systems used accumulators and/or high side refrigerant receivers, these systems had large charge plateaus and a “little extra gas” placed into these systems did not typically have irreversible effects. States, such as Wisconsin a nd California, have been re stricting the use of small cans of 134a due to the high GWP of 134a, and a desire to limit these emissions . Can suppliers have begun distributing cans that allow for multiple char ges with the same can with re-sealable valve cores in the can head. With the can modifications have also come trigger dispensers that may include a small charging gauge for more accura te and easy DIY and small professional shop charging. Given the low GWP of HFO-1234yf compared to 134a, th is rationale for eliminating small cans use for HFO-1234yf is non-existent. Th e changes made to the can due to the 134a concerns will also be helpful in minimizing exposure to HFO-1234yf.

Honeywell has chosen to determine experimentally the actual refrigerant concentrations during DIY service leakages in a closed gara ge with still air. Concentrati on measurements were collected at likely breath locations (notlocations buried inside the engine co mpartment) and still represent very conservative DIY exposure during different serv ice scenarios due to the confluence of many additional factors present during actual DIY vehicle se rvice, such as cooling fan operation, open garage doors (or outdoor environment), movement of the person, wind velocity, etc. We expect these experimental measurements to help facili tate aftermarket small can producers to develop charging instructions to guide consumers toward successful and safe recharge procedures for systems with HFO-1234yf.

Section 2: CALIBRATION OF EXP ERIMENTAL MEASUREMENT DEVICES

The measurement of refrigerant concentrations was conducted with Henze-Hauck gas sensors utilizing a platinum wire to measure the change in thermal conductivity of the gas flowing through the measurement cell, Figure 1. As the thermal conductivity of the gas ch anges as a response to refrigerant concentration, the measurement circuit vari es the power to the circuit in order to hold the temperature of the wire constant.Page 3 of 14 Figure 1. Henze-Hauck Gas Sensor Measurement Principle

To calibrate the Henze-Hauck gas sensors, a NIST Traceable Environics Series 2000 Gas Mixer (S/N 5914900001) with flow repeatabili ty of ±0.05% was utilized.

Environics Series 2000 Gas Mixer

The Environics Series 2000 contains a libra ry of common industrial gases (air, He, N2, hydrocarbons, etc) with a stated accuracy of ±1.0% F.S flow. However, R134a or R-1234zeE was not included in the online library and the determin ation of the gas mixer mass flow controllers was necessary. Environics provides a first order estimation of the th ermal mass flow meter K-factor based on the relationship between gas density and heat capacity.

ܥ

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ܥ

௥௘௙ ൌ ܰ ௙௘௥ ܦ ௙௘௥ ܥ ௙௘௥,௣ ൌ 1.00

1.250 ݃ ݎ݁ݐ݈݅ 0.249 כ ݈ܿܽ ܭ‐݃ ൌ 3.215 for N ଶ at STP

K‐factor ൌ ܥ ௦௚௔ ܥ

௙௘௥

Where V i is the volume fraction of each of the gases (R-134a and air), N i is a factor for the molecular structure (monatomic = 1.01, diatomic = 1.00, triatomic = 0.94, polyatomic = 0.88), D i is the density of the gas in g/liter at STP (0°C and 101.3 kPa), and C p,i is the heat capacity of the gas in cal/g-K at 25 °C and 101.3 kPa. The parameters for R-134a and R-1234zeE are shown in Table 1 along with the calculated K-factor.

Table 1. Environics Gas Mixer K-factor parameters Gas N i D i 0 °C, 101.3 kPa g/liter C p,i 25 °C, 101.3 kPa cal/g-K cal. K-factor per N 2 0°C, 101.3 kPa actual K-factor per N 2 0°C, 101.3 kPa R-134a 0.88 4.686 0.203 0.287 0.299 R-1234zeE 0.88 5.260 0.212 0.245 0.261Page 4 of 14 The K-factor was then calibrated by setting mass flow rate (90% of F.S.) and measuring the rate of change in the weight as refrigerant was drawn fr om a cylinder placed atop a NIST traceable MettlerToledo balance with accuracy: ±0.01 g or ±0.03 g/min. Conversion to the gas volume flow rate is determined by dividing the balance mass flow rate by the vapor density in Table 1 (for R-134a, ±6 SCCM). The K-factor was determined by taking the difference between the gas mixer’s indicated flow rate and the measured flow rate from the Mettler-Toledo balance, Figure 2 and Figure 3.

Figure 2. R-134a K-Factor calibration K-factor = 0.299 Figure 3. R-1234ze K-factor calibration K-factor = 0.261

Using the measured K-factor, the flow was measur ed using the Mettler-Tol edo balance for varying Full Scale flow settings, Table 2 and Table 3. The measured accuracy for the Environics, using the calibrated K-factor for the thermal mass flow controllers, is better than ±1.0% F.S flow.

Table 2. Flow Calibration For R-134a % Full Scale Flow Setting Measured Flow Flow SCCM SCCM 10% 90 94 20% 180 179 40% 360 360 50% 450 451 60% 540 543 80% 720 723 100% 900 904 Table 3. Flow Calibration for R-1234zeE % Full Scale Flow Setting Measured Flow Flow SCCM SCCM 10% 75 71 20% 150 151 40% 300 303 50% 375 372 60% 450 454 80% 600 601 100% 750 748

Henze-Hauck Gas Sensor

The Henze-Hauck Gas sensor was connected to the output of the Environics Gas mixer. The Henze-Hauck sensor contains a small onboard vapor pump to regulate a constant flow rate of sample over the sensing element. The total volum e flow rate from the gas mixer was set to 3600 SCCM using dry air with the balance of refrig erant at varying volume % refrigerant flows and allowed to flow past the gas sensor for pick by the onboard pump. An automated profile with steps -0.020 -0.015 -0.010 -0.005 0.000 0.005 0.010 0.015 0.0200.220.240.260.280.30.320.340.36input - measured (g/sec)

K-Factor -0.010 -0.005 0.000 0.005 0.0100.230.240.250.260.270.280.29input - measured (g/sec)

K-FactorPage 5 of 14 in concentration was developed to calibrate th e Henze-Hauck Gas Sensor over the concentration range from 0 vol% to 20 vol% refrigerant, Figure 5.

Figure 4. Calibration of Henze-Hauck Gas Sensor

Figure 5. Calibration profile for HenzeHauck Gas Sensor Figure 6. Typical Calibration Curve for Henze-Hauck Gas Sensor

During calibration it was noted that the Henze- Hauck sensors are sensitive enough to detect changes in air relative humidity. While a calibra tion for humidity was not performed due to the nature of intended testing, for long term testing it may be necessary if larg e humidity variations are expected. For the intended testing, it became conve nient to treat the air c onditions as a constant offset to the measured mV output of the sensor ci rcuit. A typical steady state calibration curve is included as Figure 6. The calibra tion is essentially linear output response to concentration; however, there is a small, repeatab le curvature. Using the accuracy of the Environics Gas Mixer, the reportable accuracy of the Henze-Hauck Gas Sensor over the range 0 vol% to 20 vol% refrigerant for R-134a and R-1234 zeE is better than ±0.2 vol%. Environics Series 2000 Gas Mixer Air

or N 2 Gas 1 Gas 2 Gas 3

Output

Exhaust

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

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90Refrigerant Concentration, vol%

Time, min 0 5 10 15 20 25 30 35

0% 5% 10% 15% 20% 25%Airoffset- Sensor Output, mV

Refrigerant Concentration, vol% y = 3.846e-6*x 2 + 0.00610*x
R 2 = 0.999Page 6 of 14 Refrigerant concentration testing generally invo lves accident scenarios where large amounts of refrigerant are released in rela tively short periods of time. Th erefore, the time response of the Henze-Hauck sensor was also evaluated as a simple electrical RC circuit analogy:

߬ ݒ݀ ௥ ሺ ݐ ሻ
ݐ݀ ݒ ൅ ௥ ሺ ݐ ሻ ߬ ൌ ݒ݀ ௦ ሺ ݐ ሻ
ݐ݀

ݒ

௥ ሺ ݐ ሻ ൅ ݒ ௖ ሺ ݐ ሻ ൌ ݒ ୱ ሺ ݐ ሻ

reducing develops the relationship between meas ured (indicated) con centration and actual concentration.

ݒ ୱ ሺ ݐ ሻ ൌ ߬ ݒ݀ ௖ ሺ ݐ ሻ
ݐ݀ ݒ ൅ ௖ ሺ ݐ ሻ

Where v s is the real gas concentration that is measured, v c is the measured sensor output, τ is the time constant, and t is time. To determine the time constant, τ , the large step change in concentration from 10 vol% to 0 vol%, Figure 7, was taken from the calibration profile. For determination of the time constant, th e above equation can be solved as:

ݒ ܿ ൌ ݒ ܿ,݋ ቆ 1െ݁ ൬ ݐെ
߬ ൰ ቇ

Where v c,o is the steady state sensor output. The time constant experienced with most of the HenzeHauck sensors is approximately 14 seconds.

Figure 7. Henze-Hauck time constant determination 0 2 4 6 8 10 12 14 16 18

-50 0 50 100 150 200 250 300Change in Sensor Output, mV

Time, sec Exp. Data
fit

τ = 14 secPage 7 of 14 Section 3: SETUP OF CONCENTRATION TESTS

A 1995 Toyota Corolla was used for experimental measurement of refriger ant concentration during and after small can leakage scenarios. All tests were conduced in a small enclosed garage with no air movement since an outdoor test or normal ai r movement would work to speed dilution of the refrigerant from the measurement area and lowe r concentrations. The air conditioner (engine running) must be on for practical servicing of the AC system; however, we did tests with the condenser fan on and off to investigate how quickly the fan dissipates the refrigerant. Only full can punctures of 3 mm (worst case) were investigated. Leakages took place at th e low side service port near the firewall located on the passenger si de as this would be the location of connection/disconnection of cans to service the AC system (Figure 8) . Different leakage scenarios were investigated covering the range of can releas es from half-can, full-can to double-can in both inverted and upright. We also found that the hoo d height made a difference in the refrigerant concentrations so a half height hood support was constructed to increase the refrigerant concentration. The testing matrix and summary of measurement results is shown as Table 4.

Table 4. Small Can Engine Leakage Test Conditions Test

# Can Charge Can Position Hood Position Condenser Fan Peak Breath Conc. 30 min TWA Peak Floor Conc. 30 min TWA

1 Full 340 g (12 oz) Inverted Open Full On 0.3 vol% 46 ppm 1.3 vol% 228 ppm

2 Full 340 g (12 oz) Inverted Open 1⁄2 On 0.7 vol% 224 ppm 1.7 vol% 302 ppm

3 Full 340 g (12 oz) Inverted Open 1⁄2 Off 0.7 vol% 119 ppm 2.7 vol% 376 ppm

4 2 cans, Full 680 g (24 oz) Inverted Open 1⁄2 Off 0.2 vol% 201 ppm 3.0 vol% 1,030 ppm

5 Half 170 g (6 oz) Upright Open 1⁄2 Off 0.1 vol% 183 ppm 1.2 vol% 1,312 ppm

6 Full 340 g (12 oz) Upright Open 1⁄2 Off 0.5 vol% 915 ppm 1.5 vol% 1,789 ppm

Measurements were taken with the calibrated Hen ze-Hauck refrigerant concentration sensors with an accuracy of 0.2 vol% refrigerant in air. Data was collected every 3 seconds from the initiation of the leak to a final time where the refrigerant has completely dispersed. Refrigerant samples were also taken under the engine compartment representing a worker on a creeper with breath location, 15 cm (6 in) off the floor on the driver and passe nger side (Figure 9). Re frigerant collection was also taken at the breath locations on the driver and passenger side were a person servicing the system would have their head located while be nt over the engine (Fig ure 10 and Figure 11). Additional measurements were located at the front bumper 30 cm (12 in) off the ground representing a person servicing the front of the vehicle.Page 8 of 14 Figure 8. Refrigerant Leak at Low Side Service Port Figure 9. Refrigerant Sampling under engine

Figure 10. Refrigerant Sampling Passenger Side Breath with hood 1⁄2 open. Technician pictured to show relative breathing location for scenario. Figure 11. Refrigerant Sampling Driver Side Breath with hood 1⁄2 open. Technician pictured to show relative breathing location for scenario.

Section 3: RESULTS

1) Hood Position (Full open or half) – Lowering the hood to a position of 1⁄2 that of the manufacturers original support r od length increased the refrigeran t concentration at both the above engine and below engine sampling ports. Figure 12 shows a full, inverted can (fast release) being discharged as a person is servicing the AC syst em with the hood resting on the manufacturers support and the condenser fan on. Figure 13 shows the same test with the hood open half and the face locations receiving an increase of refrigerant exposure. The front bumper concentration decrease and under e ngine concentration increase measurements demonstrate the effect of the hood directing the fl ow of air through the en gine and out the rear of the vehicle reducing recirculation. Rega rdless of the hood position, the worst case 30 minute time weighted average exposure was 302 ppm with the condenser fan on.Page 9 of 14 Figure 12. Test Case #1, full, inverted can (340 g) released at LS Service Port with hood fully open and condenser fan on.

Figure 13. Test Case #2, full, inverted can (340 g) released at LS Service Port with hood half open and condenser fan on. 0.00% 0.50% 1.00% 1.50% 2.00% 2.50% 3.00% 3.50%

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 Time, secondsRefrigerant Conc, vol% Front Ground, Driver Side 57 ppm Front Ground, Driver-Center 75 ppm Front Ground, Pass-Center 211 ppm Front Ground, Passenger Side 228 ppm Driver Side Under Engine 43 ppm Passenger Side Under Engine 50 ppm Passenger Side Worker Face 46 ppm Driver Side Worker Face 44 ppm 30 Min TWAs

0.00% 0.50% 1.00% 1.50% 2.00% 2.50% 3.00% 3.50%

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 Time, secondsRefrigerant Conc, vol% Front Ground, Driver Side 86 ppm Front Ground, Driver-Center 94 ppm Front Ground, Pass-Center 92 ppm Front Ground, Passenger Side 79 ppm Driver Side Under Engine 302 ppm Passenger Side Under Engine 277 ppm Passenger Side Worker Face 174 ppm Driver Side Worker Face 224 ppm 

### 30 Min TWAsPage 10 of 14 2) Condenser Fan (On or Off) – Turning the condenser fa n off greatly reduced the flow of air available to disperse the refrigerant from the proximity of the engine. Since the refrigerant vapor is 4x heavier than air, th e leaked vapor has the tendency due to buoyancy to flow down through the engine and disperse on the ground. Fi gure 14 shows that versus test case #2 with the condenser fan on, the refrigerant concentrati ons below the engine in creased and the breath concentrations of a worker above the engine in creased. The peak con centration of a worker under the vehicle while service was carried out above the vehicle would be exposed to 376 ppm for a 30 minute time weighted average if they are laying directly on the ground or creeper.

Figure 14. Test Case #3, full, inverted can (340 g) released at LS Service Port with hood half open and condenser fan off.

3) 2 Full Cans – While improbable that a repair scenario exists where two full cans are rapidly discharged, refrigerant concentration measuremen ts were carried out to determine the exposure with the condenser fan off and the hood in the 1⁄2 open position. The can s were released as quickly as making the connection to the sec ond can would allow (about 1 minute). Figure 8 shows the time weighted averages increased du e to the additional, second can, and the worst case 30 minute average was approximately 1000 pp m under the engine and the worker breath location above the engine was 202 ppm. 0.00% 0.50% 1.00% 1.50% 2.00% 2.50% 3.00% 3.50%

0 60 120 180 240 300 360 420 480 540 600 660 720 780 840 900 Time, secondsRefrigerant Conc, vol% Front Ground, Driver Side 136 ppm Front Ground, Driver-Center 164 ppm Front Ground, Pass-Center 345 ppm Front Ground, Passenger Side 171 ppm Driver Side Under Engine 376 ppm Passenger Side Under Engine 180 ppm Passenger Side Worker Face 120 ppm Driver Side Worker Face 115 ppm 

### 30 Min TWAsPage 11 of 14 Figure 15. Test Case #4, full, inverted cans (2 cans, 680 g) released at LS Service Port with hood open half and condenser fan off.

4) Upright leakage (half and full can) – For refrigerant cans that do not employ a resealable connection or valve, it may be expected that in the process of charging a system the entire contents of the charging can will not be used and some refrigerant will remain. We investigated the refrigerant concentrations for a can in wh ich half the contents were removed prior to leakage, and for a can which was fully puncture d and then set aside. For these cases the leakage times increased dramatically from the invert ed tests, as the leakage rate is a function of the amount of heat that can be transferred to the can from the surroundings. In our tests the garage was at 20oC (68  ̊ F). The test shows the release as the can is opened and the pressure drops, chilling the can to a lower release rate due to reduced internal can pressure. In the case of the half can, the leak conti nued for approximately 20 minutes to release the contents and the 30 minute time weighted averages (Figure 16) were 1,312 ppm for a worker under the engine laying on the ground or creeper, and 183 ppm for a worker bent over the top of the engine. For the full can release the leakage took approximately 1 hour to complete and the 30 minute time weighted averages (Figure 17) were 1,789 ppm for a worker under the engine laying on the ground or creeper, and 916 ppm for a work er bent over the top of the engine. 0.00% 0.50% 1.00% 1.50% 2.00% 2.50% 3.00% 3.50%

0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 1680 1800 Time, secondsRefrigerant Conc, vol% Front Ground, Driver Side 264 ppm Front Ground, Driver-Center 418 ppm Front Ground, Pass-Center 608 ppm Front Ground, Passenger Side 389 ppm Driver Side Under Engine 1,030 ppm Passenger Side Under Engine 758 ppm Passenger Side Worker Face 202 ppm Driver Side Worker Face 169 ppm 

### 30 Min TWAsPage 12 of 14 Figure 16. Test Case #5, half, upright can (170 g) released at LS Service Port with hood half open and condenser fan off.

Figure 17. Test Case #6, full, upright can (340 g) released at LS Service Port with hood half open and condenser fan off. 0.00% 0.50% 1.00% 1.50% 2.00% 2.50% 3.00% 3.50%

0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 1680 1800 Time, secondsRefrigerant Conc, vol% Front Ground, Driver Side 322 ppm Front Ground, Driver-Center 158 ppm Front Ground, Pass-Center 49 ppm Front Ground, Passenger Side 489 ppm Driver Side Under Engine 204 ppm Passenger Side Under Engine 1,312 ppm Passenger Side Worker Face 183 ppm Driver Side Worker Face 12 ppm 

### 30 Min TWAs

0.00% 0.50% 1.00% 1.50% 2.00% 2.50% 3.00% 3.50%

0 300 600 900 1200 1500 1800 2100 2400 2700 3000 3300 3600 3900 4200 4500 Time, secondsRefrigerant Conc, vol% Front Ground, Driver Side 226 ppm Front Ground, Driver-Center 376 ppm Front Ground, Pass-Center 505 ppm Front Ground, Passenger Side 511 ppm Driver Side Under Engine 335 ppm Passenger Side Under Engine 1,789 ppm Passenger Side Worker Face 916 ppm Driver Side Worker Face 210 ppm 

### 30 Min TWAsPage 13 of 14 Section 4: CONCLUSIONS

Exposure levels measured in our testing show that DIY servicing from 12 oz cans would not result in exposure lev els determined to be unsafe by EPA. EPA sets the single exposure Human Equivalent Concent ration (HEC) limit for 1234yf at 98,211 ppm and recommends a margin of exposu re (MOE) of greater than 30. 1

Acute exposure MOEs will be derived from the HEC determined fro m the rat studies ... The HEC of 98,211 ppm will be divided by the predic ted exposures to derive the MOE.

To determine the MOE for 1234yf, EPA adopted the box modeling r esults of the SAE CRP Final Report, 2 which was intended to be a highly conservative screening analy sis of possible repair exposures. Dr. Lewandowski 3 correctly points out that the rationale for using the box model is to determine whether, even if using worst‐case assumptions, the risk estimates are acceptable, so tha t more detailed risk characteri zation effort is unnecessary. Because the box model is a screening model, the appropriate res ponse to box modeling results that do not demonstrate the risks are acceptable is to undertake more sophisticated and sensitive tests to determine whether in fact the concentrat ions are below levels of

concern.

EPA’s box modeling found an acce ptable MOE for any of the expos ure scenarios except for the inverted can release scenario. Honeywell’s testing sho ws, however, that the box model estimates do not accurately characterize the risk of expo sure when servicing is performed with inverted cans. U sing the box model, the SAE CRP Final Report found that the upright can generated a 30 minute time‐weighted average (TWA) o f 2,493 ppm and the inverted can generated a 30 minu te TWA of 32,800 ppm inside the 0.5 m 3 engine compartment. Our testing of the upright can found that the box model may be justified as an approximation for the very slow release of can contents, which we measured at 1,789 ppm. However, in the cases of inverte d can releases, our results do not correlate to the assumptions of the box model. R efrigerant buoyancy and induced ventilation by the refrigerant release resulted in a much lower 30 min TWA for the inverted can (32,800 ppm predicted vs. 376 ppm for a single can and 1,030 ppm for full d ischarge of two cans). Thus, our test data shows a much highe r MOE for inverted can release than predicted by the box model. The results are shown below in Table 5 in terms of the predicted MOE, compared to the measured MOE.

1 “Risk Assessment Addendum for the EPA,” EPA-HQ-OPPT-2008-0918-0080 or EPA-HQOPPE-2008-0918-0034
2 EPA-HQ-OPPT-2008-0918-0078
3 EPA-HQ-OAR-2008-0664-0091Page 14 of 14 Table 5. MOEs for Different Leakage Scenarios

30 min TWA (ppm) MOE derived from EPA HEC single exposure value of 98,211 ppm

Inverted Can Release SAE 1234CRP Final Report: Gradient report 32,800 (est. box model) 3

Upright Can Release SAE 1234CRP Final Report: Gradient report 2,493 (est. box model) 39

Inverted Can Release Honeywell Vehicle Testing Two cans: 1,030 One can: 376

(measured) 95 260

Upright Can Release Honeywell Vehicle Testing 1789 (measured) 55

EPA recommends a MOE of greater than 30 for HFO‐1234yf. As Tab le 1 illustrates, the actual MOE for small can servic ing ranges from 55 to 260, well to the safe side of the acceptable risk levels recommended by EPA.

Contact Information: Dr. Christopher Seeton Christopher.Seeton@ honeywell.com 20 Peabody Street Buffalo, NY 14051