AMENDMENT FOR THE ASSESSMENT OF END-USE 

OCCUPATIONAL AND RESIDENTIAL OCCUPANT EXPOSURES TO

HCR-188C, A SAFE ALTERNATIVE HYDROCARBON

REFRIGERANT FOR WHITE GOODS SYSTEMS

PREPARED FOR:

RICHARD H. MARUYA

A.S. TRUST & HOLDINGS

PPP 469 BOX 10000

SAIPAN, MP

PREPARED BY:

8427 LAVIENTO DRIVE

SUITE 102

ANCHORAGE, ALASKA 99515

JULY 2007
A.S. Trust & Holdings HCR-188C White Goods Risk Assessment Amendment

Saipan, MP July 2007

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TABLE OF CONTENTS

1.0 INTRODUCTION ........................................................................................................1

2.0 WORKER EXPOSURES ASSOCIATED WITH HCR-188C................................................1

2.1 Occupational Exposures.............................................................................2

2.2 Flammability Concerns...............................................................................2

3.0 RESIDENTIAL OCCUPANT EXPOSURES ASSOCIATED WITH HCR-188C.........................3

3.1 Occupant Exposures ..................................................................................3

3.2 Flammability Concerns...............................................................................4
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ACRONYMS

ACGIH American Conference of Governmental Industrial Hygienists

AEGL Acute Exposure Guideline Level

AIHS Alaska Industrial Hygiene Services

EPA US Environmental Protection Agency

ppm parts per million

SNAP Significant New Alternatives Program

TLV-TWA Threshold Limit Value – Time Weighted Average
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1.0 INTRODUCTION

Alaska Industrial Hygiene Services (AIHS) has prepared this amendment to

Assessment of End-Use Occupational and Residential Occupant Exposures to HCR188C, A Safe Alternative Hydrocarbon Refrigerant for White Goods Systems (AIHS,

May 2007). This amendment was requested by A.S. Trust & Holdings to clarify 

additional information requested by the United States Environmental Protection Agency 

(EPA) under its Significant New Alternatives Program (SNAP).

This amendment specifically addresses potential exposures related to window air

conditioning units and upright freezers as part of the previous white goods assessment

that included household refrigerator units. Calculations contained in this amendment

are based on charge rates of 124.74 and 121.9 grams of HCR-188C for typical window

air conditioning units and 40 grams of HCR-188C for an upright freezer. Charge rates 

were provided to AIHS by A.S. Trust & Holdings.

2.0 WORKER EXPOSURES ASSOCIATED WITH HCR-188C

To calculate a worst-case scenario exposure for refrigeration technicians handling HCR188C, the following assumptions were made:

1. Worker exposure would occur only during the connection/disconnection of

hoses associated with charging the HCR-188C systems. The amount of

refrigerant released during this process is equivalent to 0.2 percent of the

refrigerant charge. For a window air conditioning unit charged with 124.74

grams of HCR-188C, this is equivalent to the release of 0.2495 grams per

connection/disconnection cycle. For a window air conditioning unit charged

with 121.9 grams of HCR-188C, this is equivalent to 0.2438 grams per

connection/disconnection cycle. For an upright freezer charged with 40

grams of HCR-188C, this is equivalent to 0.08 grams per

connection/disconnection cycle.

2. A total of eight connection/disconnection cycles would be completed by a

refrigeration technician during a normal 8-hour work shift.

3. HCR-188C released during a connection/disconnection cycle would be

contained within a closed “box” measuring 3 feet by 3 feet by 3 feet from the

point of discharge. This equates to a volume of 9 cubic feet (0.25 cubic 

meters), which includes the technician’s breathing zone.

4. The volume of the closed “box” provides for no ventilation or further dilution of

HCR-188C into the room where the work is being performed.

5. The time of exposure for each connection or disconnection is no more than

30 seconds. This is equivalent to a 1-minute exposure period per

connection/disconnection cycle.

6. The calculations are based on ambient conditions at normal temperature and

pressure (25 degrees Celsius, 760 millimeters Mercury), which results in a

gas volume of 24.45 liters per mole of gas.
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7. The molecular weight of HCR-188C is 49.26 grams/mole as determined by 

previous product testing and analysis.

8. The occupational exposure limit for HCR-188C is 1,000 parts per million

(ppm) based on the 2007 American Conference of Governmental Industrial

Hygienists (ACGIH) Threshold Limit Value-Time Weighted Average (TLVTWA) for aliphatic hydrocarbon gases (alkanes [C1 – C4]). The TLV-TWA is a

recommended TWA exposure limit based on an 8-hour workday, 40-hour

workweek.

9. The flammability range of HCR-188C is 2.0 to 9.5 percent by volume as 

determined by previous product testing and analysis.

10. The primary pathway of exposure is via inhalation. Protection against the

limited possibility of direct dermal contact with liquid refrigerant would be

provided by the use of protective gloves and goggles, which is common

industry practice when handling liquefied gases.

The formula used to calculate HCR-188C concentrations based on the assumptions 

described above was:

Wt. of HCR-188C x 24.45 L

ppm of HCR-188C = 49.26 g/mole x 1000 L x room volumeX 106

Where: Wt. of HCR-188C in grams

Room volume in cubic meters

2.1 Occupational Exposures

Occupational exposures are anticipated to occur based on a short-term or peak 

concentration during hose connection and disconnection, and on an 8-hour TWA

calculated from the estimated HCR-188C concentrations that occur during the peak 

exposure periods. For an air conditioning window unit containing 124.74 grams of

HCR-188C, the estimated peak concentration during a hose connection/disconnection

cycle is 495.3 ppm with an 8-hour TWA concentration of 8.3 ppm. For an air

conditioning window unit containing 121.9 grams of HCR-188C, the estimated peak 

concentration is 484.0 ppm with an 8-hour TWA concentration of 8.1 ppm. For an

upright freezer containing 40 grams of HCR-188C, the estimated peak concentration is 

158.8 ppm with an 8-hour TWA concentration of 2.65 ppm.

2.2 Flammability Concerns

The worst-case scenario exposure concentrations calculated for refrigeration technician

exposures to HCR-188C during the servicing of window air conditioning units would not

result in a flammability concern based on this model. The calculated concentration for a

unit charged with 124.74 grams of HCR-188C is equivalent to approximately 2.5 percent

of the lower flammability limit. For a window air conditioning unit charged with 121.9

grams of HCR-188C, the calculated concentration is equivalent to 2.4 percent of the
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lower flammability limit. During the servicing of upright freezers charged with 40 grams

of HCR-188C, the worst-case scenario exposure concentration is equivalent to

approximately 0.75% of the lower flammability limit.

3.0 RESIDENTIAL OCCUPANT EXPOSURES ASSOCIATED WITH HCR-188C

To calculate a worst-case scenario exposure for residential occupants, the following

assumptions were made:

1. The average size of a residential room cooled by a window air conditioning

unit is 100 square feet with 8 feet ceilings. This equates to a room volume of

800 cubic feet (22.66 cubic meters). This assumption is also made for rooms 

where an upright freezer may be placed within a residential structure.

2. The volume of the room is a closed room “box” with no ventilation, i.e.,

releases of HCR-188C would not diffuse into other areas of a residence and

ventilation through the room would not dilute the HCR-188C concentration.

3. The worst-case scenario exposure is based on an instantaneous release of

HCR-188C from a window air conditioning unit charged with 124.74 grams or

121.9 grams with complete evaporation of the refrigerant into a gas mixture.

The worst-case scenario exposure for the instantaneous release from an

upright freezer is based on a charge rate of 40 grams.

4. The calculations are based on ambient conditions at normal temperature and

pressure (25 degrees Celsius, 760 millimeters Mercury), which results in a

gas volume of 24.45 liters per mole of gas.

5. The molecular weight of HCR-188C is 49.26 grams/mole as determined by 

previous product testing and analysis.

6. The exposure limit for HCR-188C is 10,000 ppm based on the proposed 2004

Acute Exposure Guideline Level (AEGL) for propane published by the EPA

(see Appendix B).

7. The flammability range of HCR-188C is 2.0 to 9.5 percent by volume as 

determined by previous product testing and analysis.

8. The primary pathway of exposure is via inhalation. Direct dermal contact with

the refrigerant would not be anticipated for residential occupants.

9. For the calculations involving window air conditioning units, it is assumed that

100 percent of the refrigerant would escape into the residential structure in

the event of a release. This is highly unlikely to occur. Some portion of the

refrigerant would be expected to vent to the atmosphere due to the location of

the compressor and expansion valve of most residential window air

conditioning units.

The formula used to calculate HCR-188C concentrations based on the assumptions 

described above was:

Wt. of HCR-188C x 24.45 L

ppm of HCR-188C = 49.26 g/mole x 1000 L x room volumeX 106
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Where: Wt. of HCR-188C in grams

Room volume in cubic meters

3.1 Occupant Exposures

The estimated worst-case scenario exposure for residential occupants to the

instantaneous release of 124.74 grams of HCR-188C from a window air conditioning

unit would be 2,733 ppm. The estimated worst-case scenario exposure to the

instantaneous release of 121.9 grams of HCR-188C from a window air conditioning unit

would be 2,670 ppm. These values are approximately 27.3 and 26.7 percent,

respectively, of the proposed AEGL of 10,000 ppm. The estimated worst-case scenario

exposure for residential occupants to the instantaneous release of 40 grams of HCR188C from an upright freezer unit would be 876.2 ppm, which is approximately 8.8

percent of the proposed AEGL.

3.2 Flammability Concerns

The worst-case scenario exposure concentrations calculated for the instantaneous 

release of 124.74 and 121.9 grams of HCR-188C from a window air conditioning unit

would not result in a flammability concern based on this model. The calculated

concentrations are equivalent to approximately 13.7 and 13.4 percent, respectively, of

the lower flammability limit of HCR-188C. In addition, worst-case exposure

concentrations calculated for the instantaneous release of 40 grams from an upright

freezer are equivalent to approximately 4.4 percent of the lower flammability limit of

HCR-188C.