May 30, 2014 -- Final 1 

## Significant New **Alternatives Policy Pr ogram**  **Refrigeration and Air Conditioning Sector**  **Risk Screen on Substitutes for CFC -**  **12 , HCFC**  **- 22**  **, and R** **- 502**  **in Retail Food**  **Refrigeration Substitute:**  **R -**  **441 A**  **This risk screen is restricted to retail food refrigeration a pplications covered under UL 471:**  **Commercial Refrigerators and Freezers. This risk screen**  **does not contain Clean Air Act (CAA) Confidential Business Informati**  **on**

**(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 two decade s , including the Mo ntreal 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, administers the Significant New Alternatives Policy (SNAP) Program, which identifies acceptable and unacceptable substitutes for ODS in specific end -uses based on assessment of their health and environmental impacts. EPA’s decision on the acceptability of a substitute is based on the findings of a screening assessment of potential human health and envi ronmental risks posed by the substitute in specific applications. EPA has already screened a large number of substitutes in many end -use applications 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 risk screen is to suppl ement EPA’s Background Document on the refrigeration and air conditioning sector (EPA 1994) (hereinafter referred to as the Background Document) . This risk screen evaluates the potential use of R- 441A as a substitute for CFC - 12 , HCFC - 22, and R - 502 i n the retail refrigeration end -use , specifically for stand - alone commercial r efrigerators , freezers, and refrigerated display cases . Table 1 presents the composition of the proposed substitute. **Table 1**  **. Composition of R** **- 44**  **1 A**  **Constituent Chemical Formula**  **CAS Number Concentration**  **(Weight Percent) a**  Propane C 3 H 8 74 - 98 - 6 55% n - Butane C 4 H 10 106 - 97 - 8 36% Isobutane C 4 H 10 75 - 28 - 5 6% Ethane C 6 H 14 74 - 84 - 0 3% a There are no impurities of toxicological or ecological significance anticipated for this formulation. Isomers of hydrocarbons present in formulation mixture will exist, but are not considered to be an imp urity, contaminant or byproduct . Section 2 summarizes the results of the risk screen for the proposed substitute blend listed in Table 1 . The remainder of the risk screen is organized into the following sections:

 Section 3 : Atmospheric Assessment  Section 4 : Volatile Organic Compound Assessment  Section 5 : Discussion of End - Use Scenario ModeledMay 30, 2014 -- Final 2  S ection 6 : Potential Health Effects  Section 7 : Flammability Assessment  Section 8 : Asphyxiation Assessment  Section 9 : End -Use Exposure Assessment  Section 10 : Occupational Exposure Assessment  Section 11 : General Population Exposure Assessment  Section 12 : References 

### 2. **SUMMARY OF RESULTS** R - 441A is recommended for SNAP approval for the retail food refrigeration end -use for stand - alone refrigeration equipment that comply with Underwriters Laboratory (UL) Standard 471: Commercial Refrigerators and Freezers . E PA's risk screen indicates that the use of the proposed substitute will be less harmful to the atmosphere than the continued use of CFC - 12 , R - 502 , and HCFC - 22 as it is less harmful to the ozone layer, has lower climate impact, and a shorter atmospheric lifetime . Three of the four components of R- 441A

— propane, n -butane, and isobutane

—are subject to volatile organic compound (VOC) regulations u

nder the CAA (40 CFR 51.100(s)). Based on analysis of potential impacts of hydrocarbon refrigerant emissions on ground - level ozone concentrations , VOC emiss ions from the use of R - 441A in retail food refrigeration end -use for stand - alone refrigeration equipment are not anticipated to contribute significantly to ground level ozone concentrations in the United States . Itis expected that the material safety data sheet ( MSDS ) for R- 441A and good manufacturing practices will be adhered to . Additionally, it is expected that the appropriate safety and personal protective equipment (PPE) (e.g., protective gloves, tightly sealed goggles, protective work clothing, and suitable respiratory protection in case of leakage or insufficient ventilation) consistent with Occupational Safety and Health Administration ( OSHA ) guidelines will be used during manufacture, installation and servicing, and disposal of retail food refrigeration systems using R - 441A . Because retail food refrigeration systems are to be installed in locations with adequate space and/or ventilation in accordance with EPA recommendations and the equipment maintenance manual for R- 441A , significant toxicity or flammability risk to consumers is also unlikely. Additional safeguards , including specified refrigerant conce ntration limits (RCL) of R- 441A components, are also provided by adherence to industry standards including American Society of Heating, Refrigerating and Air - Conditioning Engineers (ASHRAE) Standards 15, 1 34, 2 and 62 3 and Underwriters Laboratory (UL) Stand ard 471. 4 

### 3. **ATMOSPHERIC ASSESSMENT**  This section presents an assessment of the potential risks to atmospheric integrity posed by the use of R441 A in commercial refrigeration and freezers . The ozone depletion potential ( ODP ) , global warming potential ( GWP ) , and atmospheric lifetime (ALT) of the proposed substitute are presented in Table 2 . The proposed substitute is substantially less harmful to th e ozone layer, has lower climate impact, and a shorter atmospheric lifetime when compared to CFC - 12 , R- 502 , and HCFC - 22 . Inaddition, R- 441A also has lower climate impact and a shorter atmospheric lifetime than those predicted for other substitutes examine d in the Background Document as well as commonly utilized substitutes R - 410A and R- 404A.

1 Safety Standard for Refrig eration Systems ASHRAE Standard 15 establishes safeguards for life, limb, health, and property and prescribes safety requirements. 2 Designation and Safety Classification of Refrigerants ASHRAE Standard 34 is establishes a uniform system for assigning refe rence numbers, safety classifications, and refrigerant concentration limits to refrigerants. Safety classifications based on toxicity and flammability data are included. 3 Ventilation for Acceptable Indoor Air Quality ASHRAE Standard 62 establishes minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects. 4 UL 471: Commercial Refrigerators and Freezers establishes safety requirements for the construction, electrical system, electrical components, refrigeration system, and performance of commercial refrigerators and freezers.May 30, 2014 -- Final 3 Thus, EPA believes that the use of R- 441A would result in substantially less harm to the climate and ozone layer than the continued use of ODS and commonly used ODS su bstitutes . **Table 2**  **. Atmospheric Impacts of R** **- 441**  **A Components**  **Compared to Other Retail Food**  **Re f**  **rigerants Refrigerant**  **Ozone Depleting Potential (**  **ODP )**  **a Global Warming Potential**  **( GWP**  **) b**  **Atmospheric Lifetime in Years**  **( ALT**  **)** Propane 0 3.3 0.0 3 a n - Butane 0 4.0 0.018 c Isobutane 0 ~4 0.01 6 a Ethane 0 5.5 0.21 c CFC - 12 0.82 10,900 100 b R - 502 d 0. 2 4,650 NAe HCFC - 22 0.13 1,810 12 a HFC - 134a 0 1,430 14 b R - 404Af 0 3,922 NAg a WMO 2010 Scientific Assessment Report (2011) b IPCC 4 th Assessment Report (Forster et al. 2007) c IPCC /TEAP (2005) d R - 502 is a blend consisting of HCFC - 22 (49%) and CFC - 115 (51%) . e Atmospheric lifetimes are not given for blends, because the components separate in the atmosphere. The ALT for HCFC - 22 is 12 years and the ALT for CFC - 115 is 1,700 years (IPCC 4 th Assessment Report [Forster et al. 2007]). f R - 404A is a blend consisting of HFC - 143a (52%), HFC - 125 (44%) and HFC - 134a (4%). g Atmospheric lifetimes are not given for blends, because the components separate in the atmosphere. The ALT for HFC - 143a is 52 years, the ALT for HFC - 125 is 29 years, and the ALT for HFC - 134a is 14 years. 

### 4. **VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS** Three of the four components of R- 441A

— propane, n -butane, and isobutane

– - are regulated as VOC s under the CAA (40 CFR 51.000), and as such, emissions of R- 441A should be controlled. A separate analysis was prepared by EPA (2014) to evaluate the potential impact of the use of hydrocarbon refrigerants on ground level ozone concentrations in the United States. The analysis estimated refrigerant emissions from refrigeration and air conditioning equipment, which were assumed to contain propylene, isobutane, and

/or propane 4 under different scenarios. Under the most conservative scenario it was assumed that propylene was used in all refrigeration and air conditioning equipment. In the most realistic scenario, all three hydrocarbons were assumed to be used in certai n types of refrigeration and air conditioning equipment , depending on the proposed use of each alternative under submissions received by the SNAP Program at the time of the analysis . End -uses included in the evaluation included selfcontained refrigeration units, for which SNAP hydrocarbon applications have been received and /or UL Standards covering flammable refrigerants exist. Th e hydrocarbon emissions from these scenarios were estimated based on U.S. EPA’s Vintaging Model, and their potential contributi ons to ozone concentrations were assessed using U.S. EPA’s Community Multiscale Air Quality (CMAQ) model. CMAQ modeling was performed for April through the end of September, as these months presented the largest releases of hydrocarbon refrigerant as well as weather conditions favorable for ozone formation. The ozone concentrations were estimated for the Atlan ta, Houston and Los Angeles regions, due to their distinctive geographic setting and chronic high levels of ground level ozone, and then scaled for national emission estimates. The results of the CMAQ modeling indicated that under the most realistic scenario, hydrocarbon refrigerants could potentially increase the maximum 8 - hour average ground level ozone by lesson more than 0.15 ppb in Los Angeles, the city with the greatest ozone problem. This is roughly 0.2 percent of the current National Ambient Air Qua lity Standard (NAAQS) for ozone of 75 ppb . 4 EP A uses the maximum incremental reactivity (MIR) of ethane (0.28 g - O 3 /g - substance) as the threshold for determining whether a compound has negligible reactivity. Propylene (MIR = 11.57), isobutane (MIR = 1.34), and propane (MIR 0.56) are all considered to be reactive compounds and are therefore subject to VOC regulations.May 30, 2014 -- Final 4 In the most conservative case which assumed that the most reactive hydrocarbon, propylene, was used in all refrigeration and air conditioning equipment, there could be an incremental maximum increase of the 8 - hour average as high as 6.61 ppb ozone, or an increase of up to 9 percent of the NAAQS. However, this upper bound level of increase is not likely, as most ozone nonattainment areas are not VOC - limited (i.e., the formation of ozone in these ar eas a re not by limited by VOC emissions, but by other compounds such as nitrogen oxides [NO x ]). In addition, the analysis assumed no use of VOC - exempt refrigerants which may be used in the refrigeration and air conditioning end -uses . Based on the results of thi s analysis, VOC emissions from the use of R - 441A in self - contained retail food refrigeration equipment are not anticipated to contribute significantly to ground level ozone concentrations in the United States. 

### 5 **. DISCUSSION OF END**  **- USE SCENARIOS MODELED**  R - 4 41A has been proposed for the retail food refrigeration end -use , specifically for stand - alone commercial refrigerators, freezers, and refrigerated display cases . The submission states that R - 441A retail food refrigeration equipment will have a typical charge size of 103 grams for commercial refrigerators, 150 grams for commercial freezers, and 135 grams for refrigerated display cases ; however, UL Standard 471: Commercial Refrigerators and Freezers states that commercial refrigeration equipment containing a flammable refrigerant may have a charge size up to 150 grams of A3 refrigerant . To represent a reasonable worst - case scenario, it is assumed that a catastrophic leak of refrigerant occurs while a commercial freezer is installed at the end -use . T o account for retail food refrigeration models which c ould utilize the maximum amount of refrigerant allowed under UL 471, the reasonable worst - case scenario is modeled using a charge size of 150 grams . B ecause retail refrigeration equipment can be installed in a wide range of locations with varying room volumes , the analys i s in this risk screen conservatively assume s that the commercial refrigeration unit is located in the kitchen of a small fast food restaurant with a volume of 50 m3 that is connected to a customer area of 100 m3 ( A .S. Trust & Holdings, Inc. 2012). 5 Under the reasonable wors t - case scenario, the full charge of the unit is assumed to be emitted over the course of one minute , into the food preparation area ( 50 m3 ) with a conservative ventilation rate of 1 .5 air changes per hour (A.S . Trust & Holdings, Inc. 2012 citing Turk, et. al. 1989) . A vertical concentration gradient is also assumed since R- 441A is denser than air (specific gravity of R- 441A relative to air is 1.67 [air = 1] ) and will settle in higher concentrations closer to the ground . In order to simulate the vertical concentration gradient , 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 vo lume (Kataoka 2000 ). Table 3 details the end -use modeling assumptions used throughout the risk screen (i.e., in Sections 7, 8, and 9 ). **Table 3. End**  **- Use**  **Scenario Model Assumptions Parameter**  **Assumption** Refrigeration Unit Commercial Freezer Room Food Preparation Area of Small Fast Food Restaurant Charge S ize (g) 150 Length of R elease (minutes) 1 Room S ize (volume - m 3 ) 50 Room V entilation (air changes per hour) 1 .5 Vertical Concentration Gradient Yes

5 Additional use locations range from small fast food restaurants and convenience stores to large supermarkets and grocery stor es. The smallest minimum convenience store found during a California survey has a volume of 244 m3 (Armines 2009), and a relativel y small fast food restaurant has a volume of 317 m3 (Clarke et al, 1990). The small food preparation area (50m3 ) in a fast food restaurant (100 m3 ) is the most conservative space volume, and was therefore the volume used to represent a reasonable, worst - ca se scenario for this analysis.May 30, 2014 -- Final 5 To address the variability in installation locations and room volumes for retail food equipment, this risk screen incorporates threshold analyses in addition to the worst - case scenario modeling, in order to determine the room size and charge size r equirements to ensure that use of R- 441A in retail food refrigeration does not present risk to consumers or servicing technicians . 

### 6 **. POTENTIAL HEALTH EFFECTS**  To assess potential health risks from exposure to the proposed substitute in retail food refrigeration, EPA identified the relevant toxicity threshold values for comparison to modeled exposure concentrations for different scenarios. To protect consumers fr om the potential dangers of a catastrophic leak from the refrigeration unit, ASHRAE Standard 34 determined refrigerant concentration limits (RCLs) for the components of R- 441A which are intended to reduce the risks of acute toxicity, asphyxiation, and flammability hazards in normally occupied, enclosed spaces during refrigerant use (ASHRAE 2010b). ASHRAE Standard 15 implements the aforementioned standard, requiring that “the concentration of refrigerant in an enclosed space following a complete discharge o f a high -probability system shall not exceed the RCL” (ASHRAE 2010a). As such, this risk screen references the RCL of the R- 441A components in addition to the lower flammability limit, hypoxia NOAEL, and exposure limits, as an additional, conservative limi t to ensure that significant flammability, asphyxiation, and end -use exposure risks , respectively, do not occur. For the occupational exposure analysis, potential risks from chronic and acute worker exposure were evaluated by comparing exposure concentr ations to available occupational exposure limits. Potential risks of chronic worker exposure were evaluated using workplace guidance levels (WGL). Risks from potential short - term consumer exposures were evaluated by comparing exposure concentrations to emergency guidance levels (EGL). In the absence of an established short - term exposure limit (STEL), acute exposure guideline level (AEGL), or emergency response planning guideline (ERPG), potential short - term, end -use exposures were compared to an excursion limit, which was calculated according to the methodology described in ACGIH (2004). 6 Table 4 lists the relevant toxicity limits of each component of R- 441A, and is followed by Table 5, which provides an explanation of each toxicity limit . EPA’s approach for identifying or developing these values is discussed in Chapter 3 of the Background Document.

6 I t should be noted that this risk screen evaluates both short - term occupational and end -use (i.e., non - occupational) exposure to ethane by comparison to the excursion limit, which is typically used to evaluate short - term occupational exposure. EPA believes, however, that in the absence of an AEGL, STEL, or ERPG, the excursion limit provides a reasonable proxy. Notably, the ACGIH methodology (i.e., a calculation of three times the TLV - TWA) has also been used by DOE (2008) t o develop temporary emergency exposure limit s (TEEL) for ethane ( 3,500 mg/m3 or 2,900 ppm 15 - min TWA), which apply to the general population.May 30, 2014 -- Final 6 **Table 4**  **. Exposure Limits**  **of R** **- 441A Components**  **R -**  **441A Component**  **8 -**  **hr WGL (Long**  **- term**  **Exposure) ppm**  **EGL (Short -**  **term Exposure) ppm**  **Refrigerant Concentration**  **Limit (RCL)**  **ppm** Propane 1,000 a

(OSHA PEL ) 10,000 c , d (10 min AEGL - 1) 6,900 d (30 min AEGL - 1) 5,300 g n - Butane 1,000 b (ACGIH TLV) 6,900 e (30 min AEGL - 1) 4,000 g Isobutane 1,000 b (ACGIH TLV) 6,900 f 4,000 g Ethane 1,000 b (ACGIH TLV) 3,000 h (30 min ACGIH Excursion Limit) 2,900 i (15 - min TEEL - 1) 7,000 g

a OSHA PEL available at: http://www.cdc.gov/Niosh/npg/npgd0524.html b ACGIH TLV for aliphatic hydrocarbon gases: alkane (C 1 - C 4 ) is 1 , 000 ppm TWA (ACGIH 2012) c An IDLH of 2,100 ppm has been established for propane. However, NIOSH (1996) states that "[b]ased on acute inhalation toxicity data in humans (ACGIH 1991; Braker 1980), a value much greater than 10,000 ppm would have been appropriate. However, the revised IDLH for propane is 2,100 ppm based strictly on safety considerations (i.e., being 10% of the lower explosive limit of 2.1%)." Therefore, as this IDLH val ue is based on flammability concerns and not toxicity concerns, it is not used in the evaluation of toxicity risks in this risk sc reen. d AEGL - 1 available at: http://www.epa.gov/opptintr/aegl/pubs/tsd96.pdf e AEGL - 1 available at: http://www.epa.gov/opptintr/aegl/pubs/tsd102.pdf f Because n - Butane and isobutane have the same molecular formula, EGL for isobutane is conservatively assum ed to be that for n - Butane. However, 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 rep orted below 18,000 ppm.” g ASHRAE (2010 b ) h Calculated as three times the TLV - TWA (ACGIH 2004). i DOE (2008) **Table 3**  **. Explanation of Exposure Limit** **- Related**  **Terminology a**  **Organization Definition**  OSHA Occupational Safety and Health Administration NIOSH National Institute for Occupational Safety and Health ACGIH American Conference of Governmental Industrial Hygienists AIHA American Industrial Hygiene Association **Exposure Limit Definition**  **Explanation Short**  **- Term Exposure**  RCL Refrigerant Concentration

Limit The RCL for a refrigerant is intended to reduce the risks of acute toxicity, asphyxiation, and flammability hazards in normally occupied, enclosed spaces. The RCL for each refrigerant is the lowest of the Acute - Toxicity Exposure Limit (ATEL), Oxygen Deprivation Limit (ODL), and Flammable Concentration Limit (FCL). Determination assumes full vaporization with no removal by ventilation, dissolution, reaction, or decomposition and complete mixing of refrigerant in the space to which it is released. STEL Short - Term Exposure Limit A 15 - minute time - weighted average ( TWA) exposure that should not be exceeded at any time during a workday, even if the 8 - hour TWA is within the TLV –TWA , set by ACGIH.

AEGL b,c Acute Exposure Guideline

Level 1 AEGL - 1 is the airborne concentration of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic nonsensory effects. H owever, the effects are not disabling and are transient and reversible upon cessation of exposure. Acute Exposure Guideline Level 2 AEGL - 2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long - lasting adverse health effects or an impaired ability to escape. Acute Exp osure Guideline AEGL - 3 is the airborne concentration (expressed as ppm or mg/m3) of aMay 30, 2014 -- Final 7 Level 3 substance above which it is predicted that the general population, including susceptible individuals, could experience life - threatening health effects or death. ERPG Emergency Response

Planning Guideline 1 T he maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient health effects or perceiving a clea rly defined, objectionable odor according to AIHA. Emergency Response Planning Guideline 2 T he maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ab ility to take protective action according to AIHA. Emergency Response Planning Guideline 3 The maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hour without experiencing or developing life - threatening health effects according to AIHA. Excursion Limit d Excursion Limit Because methane (and other short - chai n alkane gases through butane) does not have a TLV - short - term exposure limit, an excursion limit may be applied. Excursions in worker exposure levels may exceed 3 times the TLV- TWA for no more than a total of 30 minutes during a workday, and under no circumstances should they exceed 5 t imes the TLV- TWA, provided that the TLV - TWA is not exceed ed according to ACGIH. 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. **Long -**  **Term Exposure** PEL Permissible Exposure Limit This is an 8 - hour time - weighted average exposure limit set by OSHA. TLV- TWA Threshold Limit Value –Time Weighted Average The TWA concentration for a conventional 8 - hour workday and a 40 - hour workweek, to which it is believed that nearly all workers may be repeatedly exposed, day after day, for a working lifetime without adverse effect according to ACGIH. a All information in this table taken from EPA (1994) except where otherwise noted. b EPA (2012) c A pplicable to emergency exposure periods ran ging from 10 minutes to 8 hours. d ACGIH (2004) According to the MSDS, exposure to R- 441A may be hazardous if inhalation, skin contact, or eye contact with R - 441A occurs. The most likely pathway of exposure is through inhalation. R - 441A can cause symptoms of asphyxiation when present in concentrations high enough to significantly lower oxygen concentrations below 19.5 percent by volume, such as headaches, ringing in ears, dizziness, drowsiness, nausea, vomiting, depression of all senses, and also unconsciousness. Under some circumstances of over exposure (i.e., oxygen levels fall below 6 percent by volume), death may occur. In addition, at hi gh concentrations, propane, a major component of the R- 441A blend, can act as a narcotic and cause central nervous system depression, including dizziness, drowsiness, and headaches. If R - 441A is inhaled, person(s) should be immediately removed and exposed to fresh air. In accordance with the MSDS, EPA further recommends that if breathing is difficult, person(s) be given oxygen, provided a qualified operator is present, and medical attention be sought. Rescuers should not attempt to retrieve victims of exp osure to R- 441A without adequate PPE. At a minimum, a self - contained breathing apparatus (SCBA) should be worn. Exposures of R- 441A to the skin may cause frostbite. In the case of dermal exposure, the MSDS for R- 441A recommends that person(s) immediately w ash the affected area with water and remove all contaminated clothing; if frostbite occurs, bathe (not rub) the affected area with lukewarm, not hot, water. If water is not available, cover the affected area with a clean, soft cloth. Alternatively, if the fingers or hands are frostbitten, warm the affected area by placing it in the armpit; gently exercise the affected part while being warmed, and seek medical attention immediately. ExposuresMay 30, 2014 -- Final 8 of R - 441A to the eyes could cause eye irritation. In case of ocular exposure, the MSDS for R- 441A recommends that person(s) immediately flush the eyes, including under the eyelids, with copious amounts of water for 15 minutes. EPA’s review of the human health impacts of this proposed substitute is contained in the publi c docket for this decision. The potential health effects of R- 441A can be minimized by following the exposure guidelines and ventilation and PPE recommendations outlined in the MSDS for R- 441A and this risk screen. 

### 7 **. FLAMMABILITY ASSESSMENT**  ASHRAE Standar d 34 classifies R- 441A a s a Class A3 refrigerant. R- 441A is flammable when its concentration in air is in the range of 2.05 percent and 9.25 percent by volume (20, 5 0 0 ppm to 92,500 ppm). In the presence of an ignition source (e.g., static electricity, a spark resulting from a switch malfunction, or a cigarette), an explosion or a fire could occur if the concentration of R- 441A were to exceed the lower flammability limit (LFL) of 20,5 0 0 ppm . As such, R - 441A may pos e a significant safety concern for workers and consumers if it is not handled carefully. The remainder of this section assesses flammability risks and summarizes the recommended measures to ensure safe handl ing and use of the refrigerant during manufacture, servicing, and end -use. **7 .1**  **Flammability Risks at Manufacture** As indicated by the submitter, the manufacture of R- 441A refrigerant (i.e., formulation mixing) and the charging of R- 441A retail food refrig eration equipment (receiving, blending. and filling operations) occurs in a closed system; all units are completely sealed before delivery and installation. As a result, releases of R- 441A during these manufacturing and installation operations in the presence of an ignition source are not anticipated. All R- 441A storage and transport equipment should be installed with safety devices that minimize the likelihood of catastrophic releases . For example, NFPA 58 Liq uefied Petroleum Gas Code (NFPA 2014 ) for liqu efied 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 R - 441A and other flammable refrigerants. EPA believes that because workers follow relevant safety standards in manufacturing facilities , the MSDS for isobutane, and OSHA requirements under 29 CFR 1910 (e.g., proper ventilati on and storage practices within manufacturing facilities to prevent fire and explosion), flammability during manufacture is not expected to be of concern. **7 .2**  **Flammability Risk at Servicing and End -**  **Use** The risk of flammability during servicing and end -use for the reasonable worst - case scenario and typical scenario (see Section 5 ) was investigated for R- 441A . Both servicing and end -use of R- 441A retail food refrigeration equipment are expected to take place in the same space (i.e., the place of installation and use) . In order to determine the potential flammability risks during servicing or end -use in case of a catastrophic release of refrigerant in a food preparation area (see Section 5 ), concentrations of R- 441A immediately following the release of refrige rant were compared to the LFL for R- 441A. The maximum instantaneous concentration of R- 441A in the lower 0.4 meters of the room at a charge size of 150 grams would be approximately 8, 490 ppm, which is 4 1 percent of the proposed substitute’s LFL (see Table 6 ). The maximum instantaneous concentration in the upper portion of the room for both modeled charge sizes is much lower, as only 5 percent of the leaked refrigerant is present in this area , which also has a greater volume than the lower 0.4 meters of the room. Table 6 presents the results of the analysis.May 30, 2014 -- Final 9 **Table 6**  **. Flammability Assessment a**  **Scenario Charge**  **Size (g)**  **Effective Room**  **Size (m 3**  **) Maximum Instantaneous** 

**Concentration (ppm)**  b ,c Reasonable Worst - Case 150 50.0 (1 , 7 70 ft 3 ) **8 ,490**  Threshold Analysis 1: Charge Size **354** 50.0 (1 , 7 70 ft 3 ) 20,050 Threshold Analysis 2: Room Size 150 **21.2 (7 4**  **9 ft 3**  **)** 20,050 **Bold font** indicates modeling results. a Cells highlighted in green are the scenarios with exposure levels deemed acceptable given various modeling assumption options b Lower Flammability Limit of R - 441A is equal to 20,5 0 0 ppm c Values provided in these columns refer to the concentration in the lower 0.4 meters of the room The results of the threshold analys i s indicate that the charge size would have to be significantly larger, or the room size smaller, than what is assumed in th e worst - case scenario (see Section 5) for a flammability risk to occur . As shown in Threshold Analysis 1, for flammability to be of concern within a room size of 50 m3 (1,770 ft 3 ) (see Table 6) , the charge size released would have to be at least 354 grams. As shown in Threshold Analysis 2, fo r flammability to be of concern for commercial freezers with a charge size of 150 grams, the volume of the room would have to be 21. 2 m3 (74 9 ft 3 ) (see Table 6 ). It is unlikely that a store or restaurant as small as that determined in the flammability threshold analysis would exist and it is further unlikely that the entire refrigerant charge would accidentally release into the convenience store. In addition, R- 441A is likely to be dispersed into the air evenly and al most instantaneously upon accidental release; the retail food refrigeration unit compressor is pressurized between 135 and 160 psi, which will cause R- 441 to be released into the room (assumed to be at atmospheric pressure of approximately 14.7 psi) under high pressure, resulting in the refrigerant’s quick and turbulent release, and subsequent mixing into the air (A.S. Trust & Holdings, Inc. 2011). EPA recommends that the ventilation requirements outlined in the MSDS for R- 441A are followed to mitigate the risk of fire or explosion during catastrophic leak during end -use or when servicing equipment using R441A. In addition, EPA recommends that retail food refrigeration equipment with charge sizes of 150 grams are not installed in enclosed areas with volume s smaller than 21. 2 m3 (74 9 ft 3 ) in order to mitigate flammability risk. Catastrophic releases of large quantities of refrigerant, especially in areas where refrigerant is stored, could result in an explosion in the presence of an ignition source . For th is reason, it is important that only properly trained and certified technicians handle R- 441A. The submitter has provided safety guidelines for handling R- 441A, which should be followed. As a further precaution, certification requirements and training pr ograms for technicians that handle R- 441A should be developed using these guidelines. 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. Furthermore, EPA recommends that consumers should not be present during servicing activities. Itis recommended that retail food refrigeration equip ment not be installed in small, poorly ventilated spaces such as very small enclosed areas or storage closets (especially as other equipment or appliances in the space would reduce the effective volume of the room). For retail food refrigeration equipment installed in larger areas, the risk of fire and explosion is minimal. Retail food refrigeration equipment installed with R- 441A should be clearly labeled as containing a flammable refrigerant and designed to prevent catastrophic leaks. The installation o f leak prevention devices would further protect against the very limited risk of explosion. B ecause relevant safety standards and the MSDS for isobutane are followed by service technicians and because isobutane refrigeration units will be installed in area s with adequate space and ventilation, EPA believes that flammability during servicing and end -use is not expected to be of concern.May 30, 2014 -- Final 10 

### 8 **. ASPHYXIATION ASSESSMENT**  The risk of asphyxiation for the reasonable worst - case scenario was investigated for R- 441A. In this section, risk of asphyxiation is assessed in three ways: 1) modeling the oxygen concentration under the charge size and room size specified in the worst - case scenario, 2) performing a threshold analysis of minimum charge size needed to cause an asphyxiation risk in the room size specified in the worst - case scenario 3) performing a threshold analysis of the maximum room size needed to cause an asphyxiation risk with the charge size specified in the worst - case scenario. This analysis does not consider ventilation or conditions that are likely to occur that would increase oxygen 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 ai r to flow in and out. As specified in Section 5 , th e reasonable worst - case scenario assumes a vertical concentration gradient . If the proposed substitute passes the screening analysis with these restrictive assumptions in place, it can be reasonably assume d that no risks of asphyxiation will be pres ent under real - world conditions. The results of the asphyxiation assessment are summarized in Table 7 below. **Table 7**  **. Asphyxiation Assessment a**  **Scenario Charge**  **Size (g)**  **a Effective**  **Room Size (m**  **3 )**  **Percent Oxygen**

**Concentration in**  **Lower 0.4 Meters**  Reasonable Worst - Case 150 50.0 ( 1770 ft 3 ) **21** Threshold Analysis 1: Charge Size **7,242** 50.0 ( 1770 ft 3 ) 12 Threshold Analysis 2: Room Size 150 **1 .0 (36.6 ft**  **3 )**  12 **Bold font** indicates modeling results. a Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options. b The typical c oncentration of oxygen in air is considered to be 21 percent (Mackenzie & Mackenzie 1995) . In order for a risk of asphyxiation to occur, the normal concentration of oxygen in air (21 percent) in the lower 0.4 meters of the room must be reduced to 12 percent. 7 Based on the worst - case scenario modeling assumptions, R- 441A in retail food refrigeration equipment does not present a significant risk of asphyxiation. As shown in Threshold Analysis 1, t he minimum charge of R - 441A necessary to reduce the oxygen levels to 12 percent in air in the lower 0.4 meters of a room of volume 50 m3 (1 , 7 70 ft 3 ) was calculated to be 7,242 grams assuming that 1) nitrogen and oxygen retain the same relative volumes in the rooms with the balance composed entirely of R- 441A, and 2) the pressure of the room does not increase significantly with the addition of the refrigerant. This amount represen ts nearly 50 times the intended charge of approximately 150 grams for a single R- 441A retail food refrigeration unit. Because this threshold modeling does not take into account any ventilation which is likely to occur, such as conditioned airflow, open do ors, or even openings at the bottom of doors that allow air to flow in and out, as mentioned above, the actual asphyxiation risk to consumers is likely to be smaller than modeled. For the Asphyxiation Threshold Scenario, the room size at which an asphyxia tion concern would exist (i.e., when the oxygen concentration in the lower 0.4 meters of the room is 12 percent) was determined. For asphyxiation to be of concern with the maximum charge size of 150 grams, the volume of the food preparation area would have to be about 1.0 m3 ( 36.6 ft 3 ) (see Threshold Analysis 2 in Table 7 ). Based on the worst - case modeling results and threshold analysis, EPA does not believe that the use of R- 441A in commercial freezers poses a significant risk of asphyxiation or impaired coordination to personnel.



### 9. **END -**  **USE EXPOSURE ASSESSMENT** 7 Twelve percent oxygen in air is the No Observed Adverse Effect Level (NOAEL) for hypoxia (ICF 1997).May 30, 2014 -- Final 11 This section presents estimates of potential end -user exposures to R- 441A and each of its chemical constituents in the event of a catastrophic release from the proposed substitute’s use in retail food refrigeration. An end -use exposure analysis was performed to examine potential catastrophic releases of R - 441A under the reasonable worst - case scenario outlined in Section 5 . For the end -use exposu

re assessment scenario, 30 - min TWA exposures for the proposed substitute were calculated using the box model described in the Background Document, which was adapted to estimate concentrations on a minute - by - minute basis. Estimates for acute/short - term end -use exposures resulting from catastrophic leakage of refrigerant from commercial freezers were examined. The analysis was undertaken to determine the 30 - minute exposures for each component of R- 441A, which were then compared to the standard toxicity limits presented in Table 4 to assess the risk to end -users. 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. **Table 8**  **. End -**  **Use Exposure Assessment a** 

**R -**  **441A Component 30**  **- minute TWA End**  **- Use**  **Exposure (ppm) Short**  **- term (30**  **- min) Exposure**  **Limits (ppm) b**  Propane 4,390 6,900 n - Butane 2,180 6,900 Isobutane 360 6,900 Ethane 350 NA a Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options. b See Table 4 for more information . Under the reasonable worst - case scenario described in Section 5 , catastrophic releases of R- 441A from a commercial freezer with a charge size of 150 grams was modeled. For a charge size of 150 grams, the estimated 30 - min TWA exposures of the components of R- 441A do not exceed 64 percent of the respective STELs. As such, use of R- 441A in commercial freezers is not anticipated to present a significant risk to end -use rs . Furthermore, these exposures were derived using fairly conservative assumptions (e.g., minimum room volume, low ventilation rate [1.5 ACH], maximum charge size) that do not necessarily reflect the typical location for R- 441A retail food refrigeration equipment installations (e.g., retail food refrigeration equipment will be installed in large food and drink establishments and supermarkets [A .S. Trust & Holdi ngs, Inc. 2012]) . To prevent exposure and potential serious side effects during larger releases, EPA proposes that the charge size for an R- 441A commercial refrigeration unit to require compliance with UL 471 in any space containing a commercial refrigeration unit , unless proper leak protection devises are in place in order to prevent exposures of isobutane beyond the recommended limits. P roper leak protection devi c es and engineering control requirements and adherence to the MSDS will further ensu

re that exposure limits are maintained below those described in Table 8. 

### 10. **OCCUPATIONAL EXPOSURE ASSESSMENT**  This section assesses potential exposures to workers during manufacture, installation, servicing, and disposal of R- 441A . As indicated by the submitter, the manufacture of R- 441A refrigerant (i.e., formulation mixing) and the charging of R- 441A retail food refrigeration equipment (receiving, blending. and filling operations) occurs in a closed system ; all units are completely sealed before delivery and installation . As a result, exposure during these manufacturing and installation operations is not anticipated. To ensure that use of the proposed substitute in retail food refrigeration does not pose an unacceptable risk to workers during servicing and disposal, occupational exposure modeling was performed using a box - model approach . For a detailed description of the methodology used for this screening assessment ,May 30, 2014 -- Final 12 the reader is referred the occupational exposure and hazard analysis described in Chapter 5 of the Background Document . Estimates of refrigerant release per event for various release scenarios and data on number of events in 20 10 were obtained from the Vintaging Model. 8 To determine the estimated level of occupational exposure for a constituent in a blend, the total anticipated release rate of the refrigerant is multiplied by the weight percent composition of each compound in the blend. For the retail food refrigeration end use, the release per event was conservatively assumed to be 0.25 percent of the equipment charge during servicing and 35 percent of the equipment charge during disposal. 9 Additionally, EPA is proposing to allow intentional venting or release of R- 441A as a refrigerant during installation, servicing, maintenance and disposal from stand - alone retail food refrigeration equipment. If venting does occur, EPA recommends that it is done in a well - ventilated area (i.e. outdoors). Therefore, s cenarios in which 100 percent of the equipment charge was released during servicing and disposal were also considered . The release rate per event was multiplied by the number of events estimated to occur over a workday. For equipment servicing , the number of events per workday was assumed to equal the maximum num

ber of units anticipated to be serviced in one day ( i.e., eight units [A .S. Trust & Holdings, Inc. 2011]) divided by eight hours per workday. These assumptions result in approximately 1 event per hour . For disposal, it was conservatively assumed that 10 units are disposed during an 8 - hour work day. The modeled exposure concentrations were compared to short - term occupational exposure limits at installation and servicing and long - term exposure limits at disposal . **10 .1**  **Occupation al**  **Exposure at Servicing**  As indicated by the submitter, when R- 441A retail food refrigeration equipment is serviced, the used refrigerant is pumped into a canister, where it is stored until it is recycled (i.e., filtered and reused) (A .S. Trust & Holdings, Inc. 2011) . During the transfer to the initial canister, incidental refrigerant releases may occur during connection and disconnection of the recharging hose fittings , which should last approximately 30 seconds per unit (A .S. Trust & Holdings, Inc. 2011) . The maximum 30 - minute time weighted average (TWA) exposure for each R- 441A constituent were estimated for the servicing exposure scenario and compared to the ir respective short term exposure limits (see Table 9 ) . The modeling results indicate that the maximum anticipated occupational exposure concentrations at no point exceed 0.3 percent of the short - term exposure limits for retail food refrigeration units with a 150 - gram charge size during the 0.25 percent or 100 percent release scenarios . Because the exposure concentrations modeled under the conservative assumptions is significa ntly lower than the exposure limits for each constituent, occupational exposure to the proposed substitute during servicing is not considered a significant risk to workers . Further, the estimated exposure s w ere derived using conservative assumptions, and represent a worst - case scenario with a low probability of occurrence. These types of systems are typically serviced by trained personnel using proper industrial hygiene techniques.

8 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 ODS and their substitutes over a period of several years across 60 different end - uses. The model tr acks 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 in operation, and the initial ODS substance that the equipment contained. 9 During servicing and disposal it is assumed that 100 percent of the refrigerant charge remains in the unit.May 30, 2014 -- Final 13 **Table 9**  **. Occupational Risk Assessment**  **at Servicing**  **a R**  **- 441A**  **Component 30**  **- minute TWA Occupational Exposure (ppm)**  **30 -**  **min Short Term Exposure Limits (ppm)**  **0.25 % Release**  **100% Release** Propane 0.05 19.2 6,900 b n - Butane 0.02 9.6 6,900 b Ethane 0.004 1.5 3,000 c Isobutane 0.004 1.6 6,900 b a Cells highlighted in green are the scenarios that are deemed to be acceptable given various modeling assumption options. b 30 min AEGL - 1 c ACGIH (2004) **10 .**  **2 Occupation**  **al Exposure at Disposal**  Disposal of R- 441A retail food refrigeration equipment is expected to occur with limited frequency (up to approximately ten disposal event s per day) at disposal facilities and with limited duration of exposure to the refrigerant charge. Potential exposures to the refrigerant during recovery and disposal are expected to occur during activities related to draining the refrigerant from the refrigeration units into cylinders (e.g., connecting of pipes). Such activities and related exposure is anticipated to occur within 15 - 30 minutes (per event/day). Table 10 displays the maximum estimated 8 - hour TWA occupational exposure levels of the components of R - 441A during disposal. Based on the assumptions described in the beginning of S ection 10 , the modeling indicates that 8 - hour worker exposure concentrations for each of the R- 441A blend components will at no point exceed 2 3 percent of th eir respective long - term exposure limits during disposal of R- 441A for retail food refrigeration units with a 150 gram charge size during the 35 percent and 100 percent release scenarios . Table 10 displays the maximum estimated 8 - hour TWA occupational exposure levels of the R- 441A constituents during disposal . Because each value is significantly lower than the exposure guidelines for each constituent, occ upational exposure to the proposed substitute during disposal is not considered a toxicity threat. Further, the estimated exposure s w ere derived using conservative assumptions, and represent a worst - case scenario with a low probability of occurrence. These types of systems are typically disposed of by trained personnel using proper industrial hygiene techniques.

**Table 10**  **. Occupational Risk Assessment at Disposal a**  **R -**  **441A Component 8**  **- Hour TWA**  **Occupational Exposure (ppm)**  **8 -**  **Hour Long Term Exposure Limits (ppm)**  35% Release 100% Release Propane 81.7 233.3 1,000 b n - Butane 40.6 115.9 1,000 c Ethane 6.5 18.7 1,000 c Isobutane 6.8 19.3 1,000 c a Cells highlighted in green are the scenarios with exposure levels deemed to be acceptable given various modeling assumption options . b OSHA PEL c ACGIH TLV Although anticipated occupational exposures are well below the exposure limits for each of the components of R- 441A, the recommendations for proper engineering controls and PPE in the MSDS for R - 441A should be followed. Adequate ventilation should always b e established during any use, handling, or storage of R- 441A. Engineering controls should include vapor - in air detection systems and local exhaust ventilation during use of R- 441A to prevent dispersion throughout the work place. In addition, an eye wash an d safety shower should be near the manufacturing facility and locations where R- 441A is stored and ready for use. In general, use of OSHA Category B or higher PPE is recommended, such as splash goggles, mechanically - resistance gloves when handling cylinder s and chemically - resistant gloves when handling the gas mixture (e.g., butyl rubber, chlorinated polyethylene, or neoprene). SCBA and fireMay 30, 2014 -- Final 14 retardant protective clothing should be worn in case of an accidental release or spill ( A.S. Trust & Holdings, Inc. 2 011 ). EPA believes that if proper handling and disposal guidelines are followed in accordance with good industrial hygiene and manufacturing practices and the MSDS for R- 441A, there is no significant risk to workers during the manufacturing, installation, servicing, and disposal of R- 441A in retail food refrigeration units . 

### 11 **. GENERAL POPULATION EXPOSURE**  **ASSESSMENT** R - 441A is not expected to cause a threat to human health in the general population when manufactured for use and used as a refrigerant in retail food refrigeration . The proposed substitute will be manufactured in a closed process and is proposed for use in closed systems, and thus, significant releases are not anticipated. At room temperature, R- 441A is a gas and, therefore, releases to grou nd or surface water are not anticipated, as R- 441A is anticipated to dissipate into the atmosphere upon release to outside air (i.e., because natural ventilation rates would be higher and there is no enclosed space to keep R - 441A concentrated). Should air releases during manufacturing operations occur, engineering controls should be used (e.g. carbon absorption scrubbers) to collect R- 441A and prevent the release of R- 441A to the atmosphere. EPA believes that by using proper engineering controls and by foll owing disposal and containment recommendations outlined in the proposed substitute’s MSDS, exposure to R- 441A is not expected to pose a significant toxicity risk to the general population .May 30, 2014 -- Final 15 

### 12 **. REFERENCES**  Armines. 2009. Inventory of Direct and Indirect GHG Emissions from Stationary Air C o nditioning and Refrigeration S o urces, with Special Emphasis on Retail Food Refrigeration and Unitary Air Conditioning. CARB A greement No. 06 - 325. ACGIH. 2 012. Guide to Occupational Exposure Values. American Conference of Governmental Industrial Hygienists. ANSI/ASHRAE . 2010a. Standard 15: Safety Standard for Refrigeration Systems . American Society of Heating, Refrigerating and Air - Conditioning Engineers, Inc. ANSI/ASHRAE . 2010b. Standard 34: Designation and Safety Classification of Refrigerants . American Society of Heating, Refrigerating and Air - Conditioning Engineers, Inc. ANSI/ASHRAE. 2013 a . Standard 62: Ventilation for Acceptable Indoor Air Quality. American Society of Heating, Refrigerating and Air - Conditioning Engineers, Inc. A.S. Trust & Holdings, Inc. 201 2 . HCR - 188C/R - 441A for Use in New Commercial Refrigerators, Commercial Freezers and Stand - Alone Refrigerated Display Cases . Significant New Alternatives Policy Program Submission to the United States Environmental Protection Agency . March 2012 . Braker W, Mossman AL. 1980. Matheson gas data book. 6th ed. Secaucus, NJ: Matheson Gas Products, pp. 615 623. U.S. 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. 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 the 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). Safeguarding the Ozone Layer and the Global Climate System. Intergovernmental Panel on climate Change Technology and Economic Assessment Panel. Cambridge University Press, UK. pp 478. Kataoka, O., M. Yoshizawa, & T. Hirakawa 2000. “Allowable Charge Limit of Flammable Refrigerants and Ventilation Requirements.” Daikin Industries. Internati onal Refrigeration and Air Conditioning Conference. Paper 506. Available online at: http://docs.lib.purdue.edu/iracc/506 . Mackenzie, F.T. and J.A. Mackenzie. 1995. Our changing planet. Prentice - Hall. NFPA. 2014 . NFPA Liquified Petroleum Gas Code. 2014 Edition.May 30, 2014 -- Final 16 OSHA. 2004. “Safety and Health Topics: Isobutane.” February 2004. Available online at: <http://www.osha.gov/dts/chemicalsampling/data/CH_247840.html>. Turk, B.H., D.T. Grimsrud, J.T. Brown , K.L. Geisling - Sobotka, J. Harrison, and R.J. Prill. 1989. “Commercial building ventilation rates and particle concentrations.” ASHRAE Transactions 95 (1): 422 - 423. Paper No. 3248 presented at the 1989 meeting of the American Society of Heating, Refrigerating, and Air - Conditioning Engineers (ASHRAE), Chicago, Illinois. UL. 2010. UL 471 : Commercial Refrigerators and Freezers . Underwriters Laboratory. U.S. Department of Energy (DOE). 2008. DOE Handbook

– Tem porary Emergency Exposure Limits For Chemicals: Methods And Practice. Available online at: http://orise.orau.gov/emi/sc apa/files/doe - hdbk 1046 - 2008_ac.pdf

. U.S. EPA. 2012. Acute Exposure Guidelines (AEGLs) Definitions. Available online at: http://www.epa.gov/oppt/aegl/pubs/define.htm . U.S. EPA. 2014. Draft Asse ssment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level Ozone Concentrations. Prepared for the U.S. EPA Stratospheric Protection Division by ICF International. February 24, 2014. WMO (World Meteorological Organization), 2011. Scientific Assessment of Ozone Depletion: 2010 , Global Ozone Research and Monitoring Project - Report No. 52, 51 6 pp., Geneva, Switzerland .