HCR-188C1 Non-CBI Risk Screen

November 6, 2009

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Significant New Alternatives Policy Program 

Refrigeration and Air Conditioning Sector

Risk Screen on Substitutes for CFC-12 and HCFC-22 in 

Household Refrigerators and Freezers

Substitute: HCR-188C1®

This risk screen does not contain Clean Air Act (CAA) Confidential Business Information (CBI) 

and, therefore, may be disclosed to the public.

1. INTRODUCTION

Ozone-depleting substances (ODS) are being phased out of production in response to a series of 

diplomatic and legislative efforts that have taken place over the past decade, including the Montreal 

Protocol and the Clean Air Act Amendments of 1990 (CAAA). The U.S. Environmental Protection 

Agency (EPA), as authorized by Section 612 of the CAAA, is developing a program to evaluate the 

human health and environmental risks posed by alternatives to ODS. The main purpose of EPA's 

program, called the Significant New Alternatives Policy (SNAP) Program, is to identify acceptable and 

unacceptable substitutes for ODS in specific end uses. 

EPA’s decision on the acceptability of a substitute is based largely on the findings of a screening 

assessment of potential human health and environmental risks posed by the substitute in specific 

applications. EPA has already screened a large number of substitutes in many end uses within all of the 

major ODS-using sectors, including refrigeration and air conditioning, solvent cleaning, foam blowing, 

aerosols, fire suppression, adhesives, coatings and inks, and sterilization. The results of these risk screens 

are presented in a series of Background Documents that are available in EPA's docket.

The purpose of this report is to supplement EPA’s Background Document on the refrigeration and air 

conditioning sector (EPA 1994) (hereinafter referred to as the Background Document) by adding to the 

list of potential substitutes for specific end-uses of CFC-12 and HCFC-22 in this sector. Proposed enduse applications considered in this analysis include new replacements for the following end uses: 

household refrigerators and freezers. The specific proposed CFC-12 and HCFC-22 substitute blend 

examined in this report is shown in Table 1. 

Table 1. Composition of HCR-188C1.

Component Weight Percent %

n-Butane

Ethane

Isobutane

Propane

The potential risks associated with use of the constituents of this blend in residential refrigeration have 

been examined at length in the Background Document. The reader is referred to this reference for a 

detailed discussion of the methodologies used to conduct this risk screen. Presently, EPA’s SNAP 

Program has not approved any hydrocarbon blends as a substitute for CFC-12 and HCFC-22 in residential 

appliance end uses, such as those intended for this substitute (i.e., household refrigerators and freezers). 

Of particular concern are the flammability risks associated with hydrocarbon blends during 

manufacturing, use, servicing, and disposal of household appliances. Occupational exposure modeling 

was performed to ensure that use of the proposed blend in the applications listed above did not pose 

unacceptable risk to workers. Consumer exposure modeling was performed to examine potential 

catastrophic releases for each of the chemical constituents of the proposed blend. Lastly, general 
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population exposure modeling was performed to ensure that the proposed blend would not pose 

unacceptable risk to the population at large. 

Section 2 of this report summarizes the results of the risk screen for the proposed substitute blend listed in 

Table 1. The remainder of the report is organized into the following sections:

 Section 3: Atmospheric Assessment

 Section 4: Flammability Assessment

 Section 5: Asphyxiation Assessment

 Section 6: Toxicity Assessment

 Section 7: Volatile Organic Compound Assessment 

 Section 8: References

2. SUMMARY OF RESULTS

HCR-188C1 is recommended for SNAP approval for household refrigerators and household freezers. 

EPA's risk screen indicates that the use of the proposed substitute and its constituents will be less harmful 

to the atmosphere than the continued use of CFC-12 and HCFC-22. No significant toxicity risks to 

workers, consumers, or the general population are expected according to occupational and consumer 

exposure modeling. 

Flammability models indicate that risks of explosion are not a concern for consumers when the substitute 

is used in refrigerators or freezers provided that the refrigerators’ and freezers’ charge sizes are 

determined according to the UL 250 Supplement SA standard (see Section 4). Caution must be used in 

manufacturing facilities and by refrigeration technicians to minimize explosion risk, while in the presence 

of large quantities of the substitute. This includes installation of proper safety equipment during 

manufacturing, transportation, and storage and providing proper training and certification to technicians. 

EPA recommends that American Society of Heating, Refrigerating and Air-Conditioning Engineers 

(ASHRAE) Standards 15 and 34 be followed. 

3. ATMOSPHERIC MODELING

This section presents an assessment of the potential risks to atmospheric integrity posed by the use of 

HCR-188C1 in the residential refrigeration sector. The ODP, GWP, and atmospheric lifetime (ALT) of 

the proposed substitute are presented in Table 2.

The environmental impacts resulting from use of HCR-188C1 are generally in the range of those 

predicted for other substitutes examined in the Background Document. The substitute is substantially less 

harmful to the ozone layer, has less climate impact, and a shorter atmospheric lifetime compared to CFC12 and HCFC-22.

Table 2. Atmospheric Impacts of HCR-188C1 Compared to CFC-12 and HCFC-22.

Refrigerant Ozone Depleting Potential 

(ODP)

Global Warming Potential -

AR4a(GWP)

Atmospheric Lifetime 

(ALT)

n-Butane 0 4.0a 0.018b

Ethane 0 5.5a 0.21b

Isobutane 0 NA 0.019b

Propane 0 3.3a 0.041b

CFC-12 1

c 10,900a 100a

HCFC-22 0.055c 1,810 a 12a

NA – Not available in IPCC 4th Assessment Report.

a

IPCC 4th Assessment Report (Forster et al. 2007).

b

IPCC/TEAP (2005).

b Available at: http://www.epa.gov/ozone/ods.html.
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4. FLAMMABILITY ANALYSIS

Due to its flammable nature, HCR-188C1 could pose a significant safety concern for workers and 

consumers if it is not handled carefully. In the presence of an ignition source (e.g., static electricity, a 

spark resulting from a closing door, or a cigarette), an explosion or a fire could occur when the 

concentration of HCR-188C1 exceeds its lower flammability limit (LFL) of 16,100 ppm. Therefore, it is 

important to ensure that the levels of HCR-188C1 do not exceed 16,100 ppm. In production facilities or 

other facilities where large quantities of the refrigerant will be stored, proper safety precautions should be 

in place to minimize the risk of explosion. White goods installed with HCR-188C1 should be clearly 

labeled as containing a flammable refrigerant charge. Furthermore, only refrigerant technicians certified 

to work with flammable refrigerants should handle these units during manufacturing, installation, 

servicing, transportation and disposal. 

To determine whether flammability would be a concern for consumers, a reasonable worst-case scenario 

analysis was performed to model catastrophic releases of the refrigerant into the room. The analysis 

models the release of charge from a refrigerator into a kitchen. An average kitchen volume is assumed to 

be 18 m3(635 ft3) or approximately 2.7 x 2.7 m (8.9 x 8.9 ft) for a square room with 2.4 m (8 ft) ceilings

(EPA 1994). The full charge of the unit is assumed to be emitted within one minute and the kitchen is

assumed to have an air flow rate of 2.5 air exchanges per hour. Given these conservative assumptions, 

the assumed “worst-case” scenario is highly unlikely. Horizontal stratification is also assumed since 

components of HCR-188C1 are denser than air and will settle in higher concentrations closer to the 

ground. In order to simulate the horizontal concentration gradient that will occur because of the weight 

differential between the refrigerant and air, it is assumed that 95 percent of the leaked refrigerant mixes 

evenly into the bottom 0.4 meter of the room, and the rest of the refrigerant mixes evenly in the remaining 

volume (Kataoka 1999).

Under catastrophic release scenarios, the concentration of HCR-188C1 in the lower stratum of the kitchen 

would be approximately 40 percent of the substitute’s LFL for the average room size assumed, as shown 

in Table 3. 

Table 3. Flammability Assessment.

Room Type/Appliance 

Type

Average Scenario Risk Scenario

Room Size 

(m3)

Instantaneous 

Concentration (ppm)

Room Size (m3) Instantaneous 

Concentration (ppm)

Kitchen/Refrigerator 18 (635 ft3) 6,628a 7.5 (265 ft3) 15,827a

a Lower Flammability Limit of HCR-188C1 is equal to 16,100 ppm

For flammability to be of concern under the conservative (protective) assumptions described above, the 

volume of the kitchen would have to be 7.5 m3 (265 ft3). Assuming a square room with a ceiling height of 

2.4 m (8.0 ft), this equates to a 1.75 x 1.75 m (5.75 x 5.75 ft) kitchen. 

To mitigate the risks of flammability at the end-use, it is recommended that HCR-188C1 refrigerators'

and freezers’ charge sizes are determined according to the UL 250 Supplement SA standard. Per the UL 

standard, the maximum permissible leak for refrigerants with limits of flammability and heat of 

combustion greater than 19,000 kj/kg (such as the components of HCR-188C1) is 50 g. Additional 

charge is not prohibited, however, if the amount of refrigerant leaked during testing does not exceed 50 

grams. Therefore, a slightly larger charge would be permissible to compensate for the refrigerant’s 

solubility in the system’s oils so long as any leaks would not exceed 50g. By ensuring HCR-188C1 

refrigerators and freezers conform to the aforementioned standard, flammability risks associated with the 

use of HCR-188C1 in these appliances should be mitigated.
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Catastrophic releases of large quantities of refrigerant during servicing and manufacturing, especially in 

areas where large amounts of refrigerant are stored, could cause an explosion. For this reason, it is 

important that only properly trained and certified refrigerant technicians handle HCR-188C1. The 

submitter has provided safety guidelines for handling HCR-188C1, which should be followed. Using 

these guidelines, certification requirements and training programs for technicians that handle HCR-188C1

should be developed. As a further precaution, HCR-188C1 storage and transport equipment should be 

installed with safety devices that minimize the likelihood of catastrophic releases. For example, NFPA 58

Liquefied Petroleum Gas Code (NFPA, 2007) for liquefied propane requires the use of overfill protection 

devices (OPD) on cylinders to minimize the likelihood of leaks. The NPFA 58 Code also contains 

propane storage and transportation requirements/guidelines. Similar equipment safety and procedural 

requirements should be developed for HCR-188C1 and other flammable refrigerants. 

It is important that the strictest standards be followed during manufacturing. It is recommended that 

refrigerants be properly stored and caution used within manufacturing facilities to minimize explosion 

risk and that workers adhere to the requirements set by OSHA under 29 CFR 1910. OSHA requirements 

include proper ventilation and storage practices within manufacturing facilities to prevent fire and 

explosion. Proper ventilation should be maintained at all times during the manufacture of equipment 

containing HCR-188C1 through adherence to good manufacturing practices. If refrigerant levels in the 

air surrounding the equipment rise above one-fourth of the lower flammability limit,1or oxygen levels in 

the room fall below 19.5% as noted in the material safety data sheet provided by the submitter, the space 

should be evacuated and re-entry should only occur after the space has been properly ventilated. 

Ventilation is also of the utmost importance to mitigate the risk of fire or explosion when servicing 

equipment using HCR-188C1. During servicing operations, technicians should ensure that proper 

ventilation is in place through the use of fans (or other mechanical ventilation devices) and portable 

refrigerant detectors should be used to alert technicians to the presence of flammable gases in the area. 

5. ASPHYXIATION

The risk of asphyxiation for a “worst-case” scenario was investigated for HCR-188C1. This analysis does 

not consider conditions that are likely to occur that would reduce the levels to which individuals would be 

exposed, such as open doors or windows, fans operating, conditioned airflow (either heated or cooled), or 

even openings at the bottom of doors that allow air to flow in and out. 

For the worst-case scenario, a release from a refrigerator in a kitchen of volume 18 m3(635 ft3), the 

maximum charge of HCR-188C1 necessary to reduce the oxygen levels to 12 percent in air2 was 

calculated assuming horizontal stratification of the refrigerant and the air. Horizontal stratification is 

assumed since components of HCR-188C1 are denser than air and will settle in higher concentrations 

closer to the ground. Assuming that nitrogen and oxygen retain the same relative volumes in the rooms 

with the balance composed entirely of HCR-188C1, and that the pressure of the room does not increase 

significantly with the addition of the refrigerant, a charge of approximately 521 g would be necessary to 

reach 12 percent oxygen in the lower stratum. This amount represents approximately 13 times the 

intended charge of approximately 40 g for a single HCR-188C1 refrigerator or freezer. Charge 

requirements to reach the same effect in the upper stratum would be even higher because of the stratum’s 

larger volume. For asphyxiation to be of concern with the proposed charge sizes, under the conservative 

(protective) assumptions described above, the volume of the kitchen would have to be about 1.3 m3(46

ft3). 

 

1 OSHA regulation 29 CFR 1910.110 considers ventilation adequate “when the concentration of the gas in a gas-air 

mixture does not exceed 25 percent of the lower flammable limit.”

2 Twelve percent oxygen in air is the No Observed Adverse Effect Level (NOAEL) for hypoxia (ICF 1997).
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The results of the asphyxiation assessment are summarized in Table 4 below. EPA does not believe that 

the use of HCR-188C1 in this end-use poses a significant risk of asphyxiation or impaired coordination to 

consumers.

Table 4. Asphyxiation Assessment.

Room Type/Appliance 

Type

Appliance 

Charge (g)

Reasonable Worst-Case Scenario Asphyxiation Threshold Scenario

Room Size (m3) Charge Causing 

Impairment (g)a

Room Size (m3) Charge Causing 

Impairment (g)a

Kitchen/Refrigerator 40 18 (635 ft3) 521 1.3 (46 ft3) 40

6. TOXICITY REFERENCE VALUES FOR SUBSTITUTES

To assess potential health risks from exposure to this substitute in the residential refrigeration sector, EPA 

identified the relevant toxicity threshold values for comparison to modeled exposure concentrations for 

different scenarios. For the occupational exposure analysis, potential risks from chronic and acute worker 

exposure were evaluated by comparing exposure concentrations to available occupational exposure limits. 

Occupational exposure limits are typically established for either an eight-hour time period for long-term 

exposure, such as the Workplace Guidance Levels (WGLs), or for a 10 to 30-minute period for short-term 

exposure, such as the Emergency Guidance Levels (EGLs), as shown in Table 5 for each of the 

components of HCR-188C1. Because they are designed to assess risks from acute exposure, emergency 

guidance levels are used to assess risks from short-term consumer exposures. Reference concentrations 

(RfCs) are used to assess risks to the general population from exposure to ambient air releases and to 

assess potential risks associated with chronic consumer exposures. A list of the relevant toxicity limits 

are shown in Table 5. Table 6 provides definitions of the acronyms used in Table 5. EPA’s approach for 

identifying or developing these values is discussed in Chapter 3 of the Background Document. 

Table 5. Toxicity Levels of HCR-188C1 Components.

HCR-188C1 Component WGL (Long-term Exposure)

ppm

EGL (Short-term Exposure)

Ppm

Reference Concentration (RfC)

mg/m3

n-Butane 800b (NIOSH REL) 6,900 ppmg (30 min AEGL-1) 0.95 mg/m3 i

Ethane 1,000d (ACGIH TLV) NA NA

Isobutane 800c (NIOSH REL) 18,000 h (NOAEL) 0.95 mg/m3 i

Propane 1,000a 

(OSHA PEL/NIOSH REL)

2,100e (NIOSH IDLH)

10,000 ppmf(10 min AEGL-1)

6,900 ppmf(30 min AEGL-1)

0.9 mg/m3 i

a OSHA PEL and NIOSH REL available at: http://www.cdc.gov/Niosh/npg/npgd0524.html.

b NIOSH REL available at: http://www.cdc.gov/NIOSH/NPG/npgd0068.html

c NIOSH REL available at: http://www.cdc.gov/Niosh/npg/npgd0350.html

d ACGIH TLV available at: http://www.cdc.gov/niosh/ipcsneng/neng0266.html.

e NIOSH IDLH available at: http://www.cdc.gov/Niosh/npg/npgd0524.html.

f AEGL-1 available at: http://www.epa.gov/opptintr/aegl/pubs/tsd96.pdf

g AEGL-1 available at: http://www.epa.gov/opptintr/aegl/pubs/tsd102.pdf

h OSHA (2004) notes the following regarding isobutane: “OSHA does not have a PEL for isobutane, which is affirmed as "generally 

recognized as safe" as a direct human food ingredient (21 CFR 184.1165). No toxic effects reported below 18,000 ppm.”

i SNAP Refrigerant Background Document, 1994.
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Table 6. Explanation of Toxicity-Related Acronymsa

Organization Definition

ACGIH American Conference of Governmental Industrial Hygienists

OSHA Occupational Safety and Health Administration

NIOSH National Institute for Occupational Safety and Health

Exposure Limit Definition Explanation

AEGL-1 Acute Exposure Guideline Level The AEGL-1 “is the airborne concentration... above which it is 

predicted that the general population, including susceptible 

individuals, could experience notable discomfort, irritation, or certain 

asymptomatic nonsensory effects. However, the effects are not 

disabling and are transient and reversible upon cessation of 

exposure” (EPA 2008a).

IDLH Immediately Dangerous to Life and 

Health

If exposed to this concentration, room occupants are expected to be 

able to escape the room within 30 minutes without experiencing 

escape-impairing or irreversible health effects.

NOAEL No Observed Adverse Effect Limit “The highest exposure level at which there are no biologically 

significant increases in the frequency or severity of adverse effect 

between the exposed population and its appropriate control; some 

effects may be produced at this level, but they are not considered 

adverse or precursors of adverse effects.”b

PEL Permissible Exposure Limit This is an 8-hour time-weighted average exposure limit set by 

OSHA. 

REL Recommended Exposure Limit This is a 10-hour time-weighted average exposure limit set by 

NIOSH.

RfC Reference Concentration A concentration “designed to protect the general population against 

adverse systemic (i.e., noncancer) effects.”

TLV Threshold Limit Value An 8-hour time-weighted average health-based concentration set by 

ACGIH. Exposure at or below this concentration is believed to “not 

create an unreasonable risk of disease or injury.” d

a All information in this table taken from EPA (1994), except where noted otherwise.

b From http://www.epa.gov/riskassessment/glossary.htm#n

c http://www.cdc.gov/niosh/npg/pgintrod.html#exposure

d http://www.acgih.org/TLV/

6.1 OCCUPATIONAL EXPOSURE 

Occupational exposure modeling was performed for the components of the proposed blend to ensure that 

use of the blend does not pose an unacceptable risk to workers. The methodology used for this screening 

assessment is based on the one used in the occupational exposure and hazard analysis described in 

Chapter 5 of the Background Document. To evaluate potential worker exposure to alternative 

refrigerants, a model called the “box” model was used. This model has been widely used for many years 

to estimate probable exposures of workers to hazardous airborne materials, and has been described in 

detail by the National Institute for Occupational Safety and Health. This model takes into consideration 

the duration and magnitude of the resulting exposure which is influenced by 1) duration and intensity of 

the release, 2) rate at which contaminated air is diluted with uncontaminated air, 3) proximity of the 

worker to the source of the release, and 4) the length of time the worker remains in the affected space. 

Estimates of refrigerant release per event for various release scenarios and data on number of events in 

2007 were obtained from the Vintaging Model.3 To determine the estimated level of occupational 

 

3

ICF International maintains the Vintaging Model for EPA in order to simulate the aggregate impacts of the ODS phaseout on 

the use and emissions of various fluorocarbons and their substitutes over a period of several years across more than 40 different 

applications. The model tracks the use and emissions of various compounds for the annual vintages of new equipment that enter 

service in each end-use. The vintage of each type of equipment determines such factors as leak rate, charge size, number of units 
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exposure for a constituent in a blend, the total release rate of the refrigerant is multiplied by the weight 

percent composition of each compound in the blend. For all end-uses the release per event was 

conservatively assumed to be 1 percent of the equipment charge during manufacturing and 3 percent of 

the equipment charge during disposal.4 The release rate per event was multiplied by the number of events 

estimated to occur over a workday. For equipment manufacturing, the number of events per workday was 

assumed to equal the number of units containing the substitute produced per plant per year divided by 240 

workdays per year.5 For the purposes of this model, it is assumed that HCR-188C1 will have a market 

penetration rate of 3.3% and that 12 production facilities will be in operation. These assumptions result in

approximately 60 – 70 events/manufacturing facility/day. This is an extremely conservative estimate, 

considering less than 100 pounds of HCR-188C1 is intended to be produced annually, for a maximum of 

1145 units produced annually or at the most five events/manufacturing facility/day.6 For disposal, it was 

conservatively assumed that 100 units are disposed during an 8-hour work day. 

The maximum time weighted average (TWA) exposure was estimated for each exposure scenario, and 

these values compared to the Workplace Guidance Levels (WGLs) for each constituent of the blend. The 

modeling results indicate that both the short-term (15-minute and 30-minute) and long-term (8-hour) 

worker exposure concentrations at no point exceed 2 percent of the WGLs. Table 7 displays the 

maximum estimated 15-minute TWA occupational exposure levels of the HCR-188C1 constituents. 

Even these maximum estimated short-term occupational levels are significantly lower than the 8-hour 

long-term or 10-hour long term WGLs, and therefore occupational exposure to any HCR-188C1

component is not considered a toxicity threat. 

Table 7. Occupational Risk Assessment

HCR-188C1 Component Maximum 15-minute TWA 

Occupational Exposure 

Levels (ppm)

Workplace Guidance 

Levels (ppm)a

Workplace Guidance 

Levels Time Period

Butane 800 10-hr TWA

Ethane 1,000 8-hr TWA

Isobutane 800 10-hr TWA

Propane 1,000 10-hr TWAb

a See Table 5 for more information.

b The WGL for Propane is set as a 1000 ppm 8-hr TWA by OSHA and a 10-hr TWA by NIOSH.

6.2 CONSUMER EXPOSURE

This section presents estimates of potential consumer exposures to HCR-188C1 in home refrigeration

appliances. A consumer exposure analysis was performed to examine potential catastrophic releases for 

each of the chemical constituents of HCR-188C1. Estimates for acute/short-term consumer exposures 

resulting from catastrophic leakage of refrigerant from residential refrigerators were examined. The 

analysis was undertaken to determine the 15- and 30-minute TWA for each component of HCR-188C1, 

which was then compared to the standard toxicity limits presented in Table 5 to assess the risk to 

consumers. However, the TWA values are fairly conservative as the analysis does not consider opened 

windows, fans operating, conditioned airflow (either heated or cooled) and other variables that would 

reduce the levels to which individuals would be exposed.

 

in operation, and the initial ODS substance that the equipment contained. 

4 During disposal it is assumed that only 90 percent of the refrigerant charge remains in the unit. 

5 Assuming 240 workdays/year = 52 weeks/year x 5 workdays/week – 10 holidays/year.- 10 vacation days

6 HCR-188C SNAP application states that less than 100 pounds of HCR-188C is intended to be produced annually. It was 

assumed the same quantity would be produced of HCR-188C1. If all of the units produced are refrigerators of charge 39.6 g a 

maximum of 1145 units will be produced annually leading to five events/manufacturing facility/day (assuming only one 

production plant is in operation and that there are 240 workdays per year).
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The scenario involves a refrigerant leak from a refrigerator into an enclosed kitchen of volume 18 m3(635 

ft3). It is assumed that the individual is present at the start of the leak and the individual remains in the 

room while the refrigerant is released. It is also assumed that horizontal stratification causes most of the 

HCR-188C1 to settle in higher concentrations closer to the ground. Considering the horizontal 

stratification is important because children, a particularly vulnerable segment of the population, breathe 

air that is closer to the ground. In order to simulate the horizontal concentration gradient that will occur 

because of the weight differential between the refrigerant and air, it is assumed that 95 percent of the 

leaked refrigerant mixes evenly into the bottom 0.4 meter of the room, and the rest of the refrigerant 

mixes evenly in the remaining volume (Kataoka 1999). Exposure concentrations for the scenarios were 

calculated using the box model described in the Background Document, which was adapted to estimate 

concentrations on a minute-by-minute basis. It was assumed that 100 percent of the unit’s charge would 

be released during a time span of 1 minute, at which time the concentration of HCR-188C1 will peak, and 

then steadily decline onwards. Refrigerant concentrations were modeled under two air change scenarios 

believed to represent the range of potential flow rates for a home, assuming flow rates of 2.5 and 4.5 air 

changes per hour (ACH) (Sheldon 1989). 

The highest concentrations of HCR-188C1 occur in the lower stratum of the room and when assuming 2.5 

ACH. The highest expected levels of consumer exposure based on this analysis are presented inTable 8

below. Even under the conservative assumptions used in the consumer exposure modeling, the estimated

15-minute consumer exposure level of the blend’s components are no more than 50% of the chemicals’

short-term toxicity limits (or in the case of ethane for which a short-term limit is not available, its 8-hour 

TWA long-term occupational exposure limit). Therefore, consumer exposure to HCR-188C1 should not 

pose a toxicity threat.

Table 8. Consumer Exposure Assessment

HCR-188C1

Component

15-minute TWA 

Consumer Exposure 

(ppm)

30-minute TWA 

Consumer Exposure 

(ppm)

Short-term Exposure 

Limits (ppm)

Butane 6,900a

Ethane NA

Isobutane 18,000b

Propane 6,900a

a 30-minute AEGL-1; see Table 5 for more information.

b NOAEL; see Table 5 for more information.

TWA = Time Weighted Average

NA = Not available

6.3 GENERAL POPULATION EXPOSURE

In the SNAP Background document for refrigerants, RfC values are available for three of the HCR-188C1 

components - propane, butane, and isobutane. Their RfC values are are 0.9 mg/m3, 0.95 mg/m3and 0.95 

m/m

3

, respectively. We assumed a conservative RfC of 0.9 mg/m3for the whole blend, and compared 

this RfC to estimated factory releases and on-site releases. This gives a ratio of exposure concentration to 

RfC that varies between 1.3 x 10-5to 1.8 x 10-1, depending on the type of release scenario. Since the 

exposure concentrations for these components are lower than the RfC values, HCR-188C1 is not expected 

to pose a toxicity threat to the general population.

7. VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS

Most of the components of HCR-188C1, except ethane, have not been exempt as a VOC under the CAA 

(40 CFR 51.000). Through regulations and standard industry practices, VOC emissions should be 

controlled. Chapter 8 of the Background Document shows that potential emissions of VOCs from all 

substitutes for all end uses in the refrigeration and air conditioning sector are likely to be insignificant 

relative to VOCs from all other sources (i.e., other industries, mobile sources, and biogenic sources). 
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Additional analysis shows that even if all HCR-188C1 produced in one year were to leak over the course 

of the year (extremely unlikely), the resulting annual VOC emissions would be only about 3x10-7percent 

of all annual anthropogenic VOC emissions.7 Further, the calculated potential VOC emissions due to use 

of HCR-188C1 in household refrigerators and freezers is equal to about 4x10-6percent of annual 

residential wood combustion emissions.8 As these emissions of HCR-188C1 are several orders of 

magnitude less than other anthropogenic emissions, including other residential emissions (i.e., residential 

wood combustion), the environmental impacts of these VOCs are not considered a threat.

8. REFERENCES

A.S. Trust & Holdings, Inc. 2009. HCR-188C New Composition. Follow-up to the HCR-188C 

Significant New Alternatives Policy Program Submission to the United States Environmental 

Protection Agency. August 2009.

A.S. Trust & Holdings, Inc. 2007. Significant New Alternatives Policy Program Submission to the 

United States Environmental Protection Agency. June 2007. 

EPA 2008a. Acute Exposure Guideline Levels: Definitions. Accessed 27 February 2009. Available at: 

<http://www.epa.gov/opptintr/aegl/pubs/define.htm>.

EPA 2008b. Volatile Organic Compounds – National Summary of VOC Emissions. Last updated 21 

October 2008. Accessed 4 March 2009. Available at 

<http://www.epa.gov/air/emissions/voc.htm>.

EPA 1994. Significant New Alternatives Policy Technical Background Document: Risk Screen on the 

Use of Substitutes for Class I Ozone-depleting Substances: Refrigeration and Air Conditioning. 

Stratospheric Protection Division. March, 1994.

Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. 

Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland. 2007. Changes 

in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007:The Physical 

Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. 

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7 This figure determined using 2002 annual VOC emissions data from EPA (2008b) and expected annual production 

levels from A.S. Trust & Holdings, Inc. (2007). It was assumed that expected annual production for HCR-188C1 

would be the same as for HCR-188C. 

8 This figure determined using 2002 annual VOC emissions data from EPA (2008b). Residential wood combustion 

is the only residential source included in the EPA (2008b) analysis.
HCR-188C1 Non-CBI Risk Screen

November 6, 2009

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NFPA, 2007. NFPA Liquified Petroleum Gas Code. 2008 Edition.

OSHA. 2004. “Safety and Health Topics: Isobutane.” February 2004. Available online at: 

<http://www.osha.gov/dts/chemicalsampling/data/CH_247840.html>.

Sheldon, L.S., et al. 1989. "An Investigation of Infiltration and Indoor Air Quality." New York State 

Energy Research & Development Authority, Report 90-11.