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

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

Saipan, MP November 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
A.S. Trust & Holdings HCR-188C White Goods Risk Assessment Amendment

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

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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). Two previous amendments (July 2007 and November 2007) were issued

by AIHS to specifically address potential exposures related to window air conditioners 

and stand alone freezer units. This amendment was prepared for 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 stand alone

freezer units with an increased refrigerant charge rate. Calculations presented in the

following sections are based on two different charge rates of 41.81 and 53.11 grams of

HCR-188C for a stand alone freezer unit. These charge rates were determined based

on test results provided by Intertek Testing Services in Report No. 3114280CRT-003

(April 9, 2007), which is attached to this amendment. During the product testing, a

refrigerator/freezer unit was charged to 25% and 35% of its normal R-134a refrigerant

capacity (113 grams) with the alternative refrigerant HCR-188C. In this amendment, the

charge rates were increased to 37% and 47% as requested by A.S. Trust & Holdings 

and EPA.

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 stand alone freezer unit charged with 41.81 grams 

of HCR-188C, this is equivalent to the release of 0.0836 grams per

connection/disconnection cycle. For a stand alone freezer unit charged with

53.11 grams of HCR-188C, this is equivalent to the release of 0.1062 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.
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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.

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 a stand alone freezer unit containing 41.81 grams of HCR-188C,

the estimated peak concentration during a hose connection/disconnection cycle is 166

ppm with an 8-hour TWA concentration of 2.8 ppm. For a stand alone freezer unit

containing 53.11 grams of HCR-188C, the estimated peak concentration during a hose

connection/disconnection cycle is 211 ppm with an 8-hour TWA concentration of 3.5

ppm.

2.2 Flammability Concerns

The worst-case scenario exposure concentrations calculated for refrigeration technician

exposures to HCR-188C during the servicing of stand alone freezer units would not

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

unit charged with 41.81 and 53.11 grams of HCR-188C is equivalent to approximately 

0.8 and 1.1 percent, respectively, of the lower flammability limit.
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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 containing a stand alone freezer unit is 

100 square feet with 8 feet ceilings. This equates to a room volume of 800

cubic feet (22.66 cubic meters).

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 stand alone freezer unit charged with either 41.81 or 53.11

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

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.

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.

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

3.1 Occupant Exposures

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

instantaneous release of 41.81 grams of HCR-188C from a stand alone freezer unit

would be 916 ppm. This value is approximately 9.2 percent of the proposed AEGL of

10,000 ppm. The estimated worst-case scenario exposure for residential occupants to

the instantaneous release of 53.11 grams of HCR-188C from a stand alone freezer unit

would be 1,164 ppm. This value is approximately 11.6 percent of the proposed AEGL

of 10,000 ppm.
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3.2 Flammability Concerns

The worst-case scenario exposure concentrations calculated for the instantaneous 

release of 41.81 and 53.11 grams of HCR-188C from a stand alone freezer unit would

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

are equivalent to approximately 4.6 and 5.8 percent, respectively, of the lower

flammability limit of HCR-188C.