HCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 1 

## 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 plac e 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 a cceptability 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 maj or 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 end use 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 Isobu tane 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 refrig erators 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, generalHCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 2 po pulation 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  Sectio n 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 . E PA'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 modeli ng. Flammability models indicate that risks of explosion are not a concern for consumers when the substitute is used in refrigerators or freezers provided that t he refrigerator s ’ and freezers’ charge sizes are determined according to th e 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 p resented 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 CFC 12 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 - AR4 a (GWP) Atmospheric Lifetime (ALT) n - Butane 0 4.0 a 0.018 b Ethane 0 5.5 a 0.21 b Isobutane 0 NA 0.019 b Propane 0 3.3 a 0.041 b CFC - 12 1 c 10,900 a 100 a HCFC - 22 0.055 c 1,810 a 12 a NA – Not available in IPCC 4th Assessment Report . a IPCC 4 th Assessment Report (Forster et al. 2007) . b IPCC/TEAP (2005). b Available at: http://www.epa.gov/ozone/ods.html.HCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 3 

### 4. FLAMMABILITY ANALYSIS Due to its flammable nature, HCR - 188C1 could pose a significant safety concern for worker s 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 low er 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 refrig erants 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 analys i s w as performed to model catast rophi c 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 ft 3 ) 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) . T he full charge of the unit is assumed to be emitted within one minute and the kitchen is assume d to have an air flow rate of 2.5 air exchanges per hour . Given these conservative assumptions, the assumed “worst - case” scen ario 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 occu r 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 (m 3 ) Instantaneous

Concentration (ppm) Room Size (m 3 ) Instantaneous Concentration (ppm) Kitchen/Refrigerator 18 (6 35 ft 3 ) 6,628 a 7 . 5 ( 265 ft 3 ) 15,827 a 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 ft 3 ). 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 si zes 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 combus tion greater than 19,000 kj/kg ( such as the components of HCR- 188C1 ) is 50 g. A dditional 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 i n 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 .HCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 4 Catastrophic releases of larg e 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 Liqu e fied Petroleum Gas C ode (NFPA , 2007 ) for liquefied propane requires the us e 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 f or 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 worker s 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 al l 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, 1 or 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. 

### V entilation 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 like ly 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 ft 3 ), the maximum charge of HCR- 188C1 necessary to reduce the oxygen levels to 12 percent in air 2 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 bal ance 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 5 2 1 g would be necessary to reach 12 percent oxygen in the lower stratum. This amount represents approximately 1 3 times the intended charge of approximately 40 g for a single HCR - 18 8C1 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 size s , under the conservative (protective) assumptions described above, the volume of the kitchen would have to be about 1.3 m3 ( 46 ft 3 ) .

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).HCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 5 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 Asses sment . Room Type/Appliance Type Appliance

Charge (g) Reasonable Worst - Case Scenario Asphyxiation Threshold Scenario

Room Size (m 3 ) Charge Causing

Impairment (g) a Room Size (m 3 ) Charge Causing Impairment (g) a Kitchen/Refrigerator 40 18 (635 ft 3 ) 521 1.3 (46 ft 3 ) 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 exposur e 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 conc entrations (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 Chapt er 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) P pm Reference Concentration (RfC) mg/m 3 n - Butane 800 b (NIOSH REL) 6,9 00 ppm g (30 min AEGL - 1) 0.95 mg/m 3 i Ethane 1,000 d (ACGIH TLV) NA NA Isobutane 800 c (NIOSH REL) 18,000 h (NOAEL) 0.95 mg/m 3 i Propane 1,000 a

(OSHA PEL/NIOSH REL) 2,100 e (NIOSH IDLH) 10,000 ppm f (10 min AEGL - 1) 6,900 ppm f (30 min AEGL - 1) 0.9 mg/m 3 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 a t: 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 avai lable 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 rec ognized 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.HCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 6 Table 6 . Explanation of Toxicity- Related Acronyms a Organization Defini tion 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 L evel 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 e xperiencing 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 pop ulation 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/pgint rod.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 releas e, 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 leve l 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 ente r service in each end - use. The vintage of each type of equipment determines such factors as leak rate, charge size, number of unitsHCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 7 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 per cent 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) exp osure 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 b oth the short - term (15 - minute and 30 - minute) and long - term (8 -hour) wo rker exposure concentrations at no point exceed 2 percent of the WGLs. Table 7 displays the maximum estimated 15 - mi nute TWA occupational exposure levels of the HCR- 188C1 constituents. Even these maximum estimate d 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 . Occupa tional 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 TWA b 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 resultin g 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 Assu ming 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).HCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 8 The scenario involves a refrigerant leak from a refrigerator into an enclosed kitchen of volume 18 m3 (635 ft 3 ). It is assumed that the individual is present at the start of th e 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 stratificat ion 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 ref rigerant 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 we re 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 whi ch 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 chemical s ’ short - term toxi city limits (or in the case of ethane for which a short - term limit is not available , its 8 -hour TWA long - t erm occupational exposure limit) . T herefore, consumer exposure to HCR - 188C 1 should not pose a toxicity threat. Table 8 . Cons umer Exposure Assessment

HCR - 188C1 Component 15 - minute TWA

Consumer Exposure (ppm) 30 - minute TWA

Consumer Exposure (ppm) Short - term E xposure

L imits (ppm) Butane 6,900 a Ethane NA Isobutane 18,000 b Propane 6,900 a 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/m3 and 0.95 m/m3 , respectively. We assumed a conservative RfC of 0.9 mg/m3 for the whol e 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 - 5 to 1.8 x 10 - 1 , depending on the type of release scenario. Since the exposure concentrati ons 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) . T hrough 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 refrige ration 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 ).HCR - 188C1 Non - CBI Risk Screen Novembe r 6 , 2009 Page 9 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 3 x10 - 7 percent of all annual anthropogenic VOC emissions. 7 Further, the calculated potential VOC emissions due to use of HCR- 188C1 in household ref rigerators and freezers is equal to about 4 x10 - 6 percent of annual residential wood combustion emissions. 8 As these emissions of HCR- 188C1 are several orders of ma gnitude 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 Submis sion 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 Cons tituents 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. Marquis, K .B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. ICF. 1997. Physiological Effects of Alternative Fire Protection Agents - Hypoxic Atmospheres Conference. Stephanie Skaggs prepared th e proceedings of the conference held May 22, 1997 in New London, CT. IPCC/TEAP. 2005. Bert Metz, Lambert Kuijpers, Susan Solomon, Stephen O. Andersen, Ogunlade Davidson, José Pons, David de Jager, Tahl Kestin, Martin Manning, and Leo Meyer (Eds). Cambridge University Press, UK. pp 478. Kataoka. 1999. “Allowable Charge Limit of Flammable Refrigerants and Ventilation Requirements.” Draft Proposal. O. Kataoka/Daikin/Japan, June, 1999.

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 wo uld 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 Novembe r 6 , 2009 Page 10 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.