March 29, 2016 – Final 1 

## Significant New Alternatives Policy Program Refrigeration and Air Conditioning Sector

Risk Screen on Substitutes in Very Low Temperature Refrigeration

Substitutes: Ethane (R-170) and Propane (R-290)

This risk screen is restricted to very low temperat ure (VLT) refrigeration applications covered

under UL 471: Commercial Refrigerators and Freezers

.

This risk screen does not contain Clean Air Act (CA A) Confidential Business Information (CBI) and, therefore, may be disclosed to the public. Bra ckets [ ] represent redacted CBI content.



### 1. INTRODUCTION Ozone-depleting substances (ODS) are being phased o ut of production in response to a series of diploma tic and legislative efforts that have taken place over the past two decades, including the Montreal Protoc ol 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 unacceptab le substitutes for ODS in specific end-uses based o n assessment of their health and environmental impact s. EPA’s decision on the acceptability of a substitute is based on the findings of a screening assessment of potential human health and environmental risks pose d by the substitute in specific applications. EPA has already screened a large number of substitutes in m any end-use applications within all of the major OD Susing sectors, including: refrigeration and air con ditioning, solvent cleaning, foam blowing, aerosols , fire suppression, adhesives, coatings and inks, and ster ilization. The results of these risk screens are pr esented in a series of Background Documents that are available in EPA's docket. The purpose of this risk screen is to supplement EP A’s Background Document on the refrigeration and ai r conditioning sector (EPA 1994) (hereinafter referre d to as the Background Document). This risk screen evaluates the potential use of ethane (R-170) and p ropane (R-290) as substitutes in very low temperatu re (VLT) refrigeration, specifically in VLT freezers. VLT refrigeration systems require maintaining temperatures at approximately -86°C (-176°F) or low er. This type of equipment requires extremely relia ble refrigeration cycles to maintain low temperatures a nd must meet stringent technical standards that do not typically apply to refrigeration systems (EPA 2013) . Table 1 presents the composition of the proposed substitute. Table 1. Composition of Ethane and Propane

Constituent Chemical Formula CAS Number Concentration (Weight Percent) a Ethane (R-170) C 2 H 6 ; CH 3 CH 3 74-84-0 >99%
Propane (R-290) C 3 H 8 74-98-6 >99.7%

a Negligible amounts of impurities may be present.
Section 2 of this report summarizes the results of the risk screen for the proposed substitute. The r emainder of the risk screen is organized into the following sections:March 29, 2016 – Final 2 • Section 3: Atmospheric Assessment

• Section 4: Volatile Organic Compound Assessment

• Section 5: Discussion of End-Use Scenarios Modeled

• Section 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 Ethane and propane are recommended for SNAP approva l for use in VLT freezers, included under Underwriters Laboratory (UL) Standard 471: Commerci al Refrigerators and Freezers. Ethane is currently SNAP-approved as a refrigerant in VLT freezers. 1 This risk screen evaluates the use of ethane and p ropane in a two-stage cascade refrigeration system and als o recommends propane as an acceptable refrigerant f or use in VLT freezers, whether using a single refrige ration cycle or in a two-stage system. EPA’s risk s creen indicates that the use of the proposed substitutes will be less harmful to the atmosphere than the con tinued use of ODS other commonly used refrigerants as they are less harmful to the ozone layer, have lower climate impact, and shorter atmospheric lifetimes. No significant asphyxiation risks to personnel or t oxicity risks to workers, personnel, or the general populat ion are expected. Ethane’s contribution to volatile organic compound (VOC) emissions is not significant, as eth ane is exempt under CAA regulations (40 CFR 51.100(s)). Although propane is regulated as a VOC, VOCs from the use of propane are not anticipated t o result in greater impacts on local air quality in t he United States than other available options based on analysis of potential propane emissions. It is expected that procedures in the safety data s heets (SDS) for ethane and propane and good manufacturing practices will be adhered to. Additio nally, it is expected that the appropriate safety a nd personal protective equipment (PPE) (e.g. protectiv e gloves, tightly sealed goggles, protective work clothing, and suitable respiratory protection in ca se of leakage or insufficient ventilation) consiste nt with Occupational Safety and Health Administration (OSHA ) guidelines will be used during manufacture, installation and servicing, and disposal of VLT fre ezers using ethane and propane. Because units are t o be installed in locations with adequate space or venti lation in accordance with the VLT freezer manual fo r ethane and propane, as discussed in greater detail in Section 9, significant toxicity or flammability risk to workers is also unlikely. Additional safeguards, including the refrigerant co ncentration limits (RCL) for ethane and propane, ar e provided in industry standards such as American Soc iety of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standards 15, 2 34, 3 and 62 4 and Underwriters Laboratory (UL) Standard 471. 5 The RCL for a refrigerant is intended to reduce the ris ks of acute toxicity, asphyxiation, and flammabilit y

1 Ethane was listed as acceptable for use, subject t o use conditions, in very low temperature refrigera tion equipment on April 10, 2015 (80 FR 19454).
2 Safety Standard for Refrigeration Systems ASHRAE St andard 15 establishes safeguards for life, limb, he alth, and property and prescribes safety requirements.
3 Designation and Safety Classification of Refrigeran ts ASHRAE Standard 34 is establishes a uniform syst em for assigning reference numbers, safety classifications, and refr igerant concentration limits to refrigerants. Safe ty classifications based on toxicity and flammability data are included.
4 Ventilation for Acceptable Indoor Air Quality ASHRA E Standard 62 establishes minimum ventilation rates and other measures intended to provide indoor air quality that is acce ptable to human occupants and that minimizes advers e health effects.
5 UL 471 Standard for Commercial Refrigerators and Fr eezers establishes safety requirements for the cons truction, electrical system, electrical components, refrigeration system , and performance of commercial refrigerators and f reezers.March 29, 2016 – Final 3 hazards in normally occupied, enclosed spaces. This and other exposure terminology are defined in Sect ion 6.


### 3. ATMOSPHERIC ASSESSMENT This section presents an assessment of the potentia l risks to atmospheric integrity posed by the use o f ethane and propane in VLT freezers. The ozone depletion po tential (ODP), global warming potential (GWP), and atmospheric lifetime (ALT) of the proposed substitu tes are presented in Table 2. The proposed substitu tes are substantially less harmful to the ozone layer, have a lower climate impact, and shorter atmospheri c lifetimes when compared to refrigerants currently u sed in these end-uses, such as CFC-12, CFC-13, R13B1, and R-503. In addition, ethane and propane ha ve lower climate impacts and shorter atmospheric lifetimes than other utilized VLT refrigerant subst itutes, such as R-508B and HFC-23. Table 2. Atmospheric Impacts of Ethane and Propane Compared to Other VLT Refrigerants Refrigerant Ozone Depleting Potential (ODP) a Global Warming Potential (GWP) b Atmospheric Lifetime in Years (ALT) b Ethane 0 6 c 0.17 d Propane 0 b 3 0.03 a R

- 13B1 (Halon 1301) 15.9 7,140 65 CFC

- 12 0.82 10,900 100 CFC

- 13 1 14,4 0 0 640 R

- 503 0.599 14,560 NA e R

- 508B 0 13,396 NA f HFC

- 23 0 14, 800 270

a World Meteorological Organization (WMO) 2010 Scien tific Assessment Report (2011)
b Intergovernmental Panel on Climate Change (IPCC) 4 th Assessment Report (Forster et al. 2007), unless oth erwise noted.

c Global Cooling Inc. (2012)
d Gonzalez et al. (2011)

e R-503 is a blend consisting of CFC-13 (60%) and HF C-23 (40%). The ALT for CFC-13 is 640 years and the ALT for HFC-23 is 270 years.
f R-508B is a blend consisting of HFC-23 (46%) and p erfluoroethane (PFC-116) (54%). The ALT for HFC-23 is 222 years and the ALT for PFC116 is 10,000 years.


### 4. VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS Ethane is exempt from the definition of VOC under C AA regulations (40 CFR 51.100(s)). Therefore, environmental impacts from the release of ethane as a VOC are not a significant concern. Propane is regulated as a VOC under CAA regulations (40 CFR 51.100 [s]). Emissions of propane should be controlled according to CAA and other regulation s by adhering to standard industry practices. EPA prepared a separate analysis in 2014 6 and a follow-on analysis in 2016 7 to evaluate the potential impact of the use of hydrocarbon refrigerants on gr ound-level ozone concentrations in the United State s. These analyses estimated refrigerant emissions from refrigeration and air conditioning equipment, whic h were assumed to contain propylene, isobutane, and/o r propane 8 under different scenarios and compared their resulting relative increases in ozone concent rations against the National Ambient Air Quality St andard (NAAQS) for ozone of 70 ppb. 9 Under the most conservative scenario it was assume d that propylene was used in all refrigeration and air conditioning equi pment. In more realistic scenarios, all three hydro carbons (and/or blends thereof) were assumed to be used in certain types of refrigeration and air conditioning

6 Assessment of the Potential Impact of Hydrocarbon R efrigerants on Ground Level Ozone Concentrations (February 2014) [EPAHQ-OAR-2013-0748-0003]
7 Follow-on Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level Ozone Conc entrations (March 2016)
8 EPA uses the maximum incremental reactivity (MIR) o f ethane (0.28 g-O 3 /g-substance) as the threshold for determining whet her 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.
9 On October 1, 2015, EPA strengthened the NAAQS for ground-level ozone to 70 ppb from 75 ppb, based on scientific evidence about ozone’s effects on public health and welfare (EPA 2015).March 29, 2016 – Final 4 equipment, depending on the proposed use of each al ternative under submissions received by the SNAP program at the time of the analysis. End-uses in the evaluation included a number of typ es of smaller, self-contained refrigeration and roo m airconditioning units for which SNAP hydrocarbon appli cations have been received and/or UL Standards covering flammable refrigerants exist. 10 The hydrocarbon emissions from these scenarios wer e estimated based on EPA’s Vintaging Model, and their potential contributions to ozone concentrations were assesse d using EPA’s Community Multiscale Air Quality (CMAQ) model. 11 CMAQ modeling was performed for April through the e nd of September, as these months presented the largest releases of hydrocarbon refrigerant as well as weather conditions favorable for ozone formatio n. The ozone concentrations were estimated for the Atlanta , Houston, and Los Angeles regions, due to their distinctive geographic setting and chronic high lev els of ground-level ozone, and then scaled for nati onal emission estimates. The results of the CMAQ modeling indicated that und er the most conservative case which assumed that th e most reactive hydrocarbon, propylene, was used in a ll refrigeration and air conditioning equipment, th ere could be an incremental maximum increase of the 8-h our average as high as 7.8 ppb ozone in 2040. By comparison, the most realistic scenario, in which a mixture of hydrocarbon refrigerants are used, refr igerant emissions could potentially increase the maximum 8- hour average ground-level ozone by no more than 2.5 ppb in 2040 in Los Angeles, the city with the great est ozone problem. This upper bound level of increase for the realisti c scenario is not likely, as most ozone nonattainme nt areas are not VOC-limited (i.e., the formation of ozone i n these areas is not 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 will also likely be used in refr igeration and air conditioning end-uses along with hydrocarbon refrigerants. Based on the results of t his analysis, VOC emissions from the use of propane in VLT refrigeration are not anticipated to contribute significantly to ground level ozone concentrations in the United States.



### 5. DISCUSSION OF END-USE SCENARIOS MODELED Ethane has already been SNAP-approved for use in VL T freezers. Based on the application provided by th e submitter, this risk screen evaluates the use of bo th ethane and propane in a two-stage cascade VLT refrigeration system. This risk screen also covers the use of propane in VLT using a single refrigerat ion cycle.
[ ] The submission states that the VLT freezers will ty pically contain 98 grams of ethane and 120 grams of propane (Eppendorf 2015), with a maximum charge siz e of 150 grams per refrigerant loop according to UL Standard 471. Both the typical (i.e., 98 grams and 120 grams) and maximum (i.e., 150 grams) charge siz es are modeled in this risk screen. To represent a reasonable worst-case scenario, it i s assumed that a catastrophic leak of refrigerant o ccurs while the VLT freezer is installed at the end-use. VLT freezers are typically used in bio-repositories
, pharmaceutical production facilities, and universit y laboratories. In these locations, the freezers ar e typically clustered side by side, spaced 25.4 centi meters (10 inches) apart and in laboratory rooms wi th 3.0- meter (10-foot) ceilings (Carnegie Mellon Universit y 2007). A typical laboratory module has a minimum width of approximately 10 feet, but will vary in le ngth based on the number of modules configured in a

10 VLT refrigeration was not included as an end-use in the CMAQ modeling assessment. Because the incremen tal changes in ground-level ozone were insignificant between all m odeled refrigeration and air-conditioning equipment , use in VLT refrigeration is not expected to significantly affect the estimat ed impact on ground-level ozone concentration.
11 VM version VM_IO file_v4.4_10.13.14 and CMAQ model version 5.0.2 were used in this analysis.March 29, 2016 – Final 5 row, typically ranging up to an ideal length of app roximately 33 feet long (National Institutes of Hea lth 2008). Therefore, the analysis in this risk screen conservatively assumes that the VLT freezer is inst alled in one laboratory module that is approximately 3.0 met ers (10 feet) wide, 3.0 meters (10 feet) long, and 3.0 meters (10 feet) high, which corresponds to an effe ctive volume of 28 m 3 (1,000 ft 3 ), with an effective floor area of 9.3 m 2 (100 ft 2 ) (i.e., excluding the space filled by the freezers and other items in the laboratory).

Under the reasonable worst-case scenario, the full charge of both refrigerant loops in the unit are assumed to be emitted over the course of one minute into th e laboratory with 4 air changes per hour (ACH) (E.O

. Lawrence Berkeley National Laboratory 2013). It is not likely that the two refrigerants would mix in t he air during release, because the refrigerants have diffe rent densities relative to air. Ethane has approxim ately the same density as air (specific gravity of ethane rel ative to air is 1.05 [air = 1]), and, therefore, wh en the full charge is released, the proposed substitute is expe cted to disperse evenly and immediately throughout the room. Propane is denser than air (specific gravity of propane relative to air is 1.52 [air = 1]), so i t will settle in higher concentrations closer to the ground. Ther efore, a vertical concentration gradient is assumed in the worst-case scenarios for propane. It was assumed th at an individual is present at the start of the lea k and remains in the room until the charge is completely released. Table 3. End-Use Scenario Model AssumptionsTable 3 details the assumptions in the m odels throughout this risk screen (i.e., in Section s 7, 8, 9, and 10). Table 3. End-Use Scenario Model Assumptions

Parameter Assumption Refrigeration Unit VLT Freezer Room Laboratory Module Charge Size s (g) Ethane: 98 a and 150 b Propane: 120 a and 150 b Length of Release (minutes) 1 Effective Room Size (volume

- m 3 ) 28 (1,000 ft 3 ) Room Ventilation ( ACH ) 4 c Vertical Concentration Gradient Yes d

a Eppendorf (2015)
b UL 471

c E.O. Lawrence Berkeley National Laboratory (2013)
d Propane only.
EPA recognizes that VLT freezers may be placed in a variety of room types with different sizes and ventilation rates. In addition, more than one VLT f reezer may be installed in the same space, as the u nits are fairly small with a typical volume of 1.71 m 3 (60 ft 3 ) and dimensions of 1.0 m x 0.87 m x 2.0 m (3.3 ft x 2.9 ft x 6.6 ft), which is similar in capacity to a hou sehold refrigerator (Eppendorf 2016). When units ar e installed in smaller, enclosed spaces, there is a h igher risk for flammability, asphyxiation, or toxic ity concerns. To address these concerns, this risk scre en incorporates threshold analyses in addition to t he reasonable worst-case scenario modeling. The result s from the threshold analyses are used to establish guidelines for choosing an effective room size and charge size such that use of ethane and propane in VLT freezers does not present risk to end-users or serv icing technicians.



### 6. POTENTIAL HEALTH EFFECTS To assess potential health risks from exposure to t he proposed substitutes in VLT freezers, EPA identi fied the relevant toxicity threshold values for comparis on to modeled exposure concentrations for different scenarios. To protect consumers from the potential dangers of a catastrophic refrigerant leak from a V LT freezer, ASHRAE Standard 34 determined RCLs to redu ce the risks of acute toxicity, asphyxiation, and flammability hazards in occupied spaces (ASHRAE 201 0b). ASHRAE Standard 15 implements the aforementioned standard, requiring that “the concen tration of refrigerant in an enclosed space followi ng a complete discharge of a high-probability system sha ll not exceed the RCL” (ASHRAE 2010a). As such, thi sMarch 29, 2016 – Final 6 risk screen references the RCL in addition to the l ower flammability limit, hypoxia No Observed Advers e Effect Level (NOAEL), and exposure limits, as an ad ditional, conservative limit to ensure that signifi cant flammability, asphyxiation, and end-use exposure ri sks, respectively, do not occur. For the occupational exposure analysis, potential r isks from chronic worker exposure to ethane and pro pane concentrations were evaluated by comparison to the workplace guidance level (WGL). In the absence of a n established short-term exposure level (STEL), acute exposure guideline level (AEGL), or an emergency response planning guideline (ERPG), potential short -term, end-use exposures to ethane was compared to its excursion limit. 12 Table 4 lists the relevant toxicity limits for et hane and propane, followed by Table 5 which describes each of these exposure limits in mo re detail. EPA’s approach for identifying or develo ping these values is discussed in Chapter 3 of the Backg round Document. Table 4. Exposure Limits of Ethane and Propane

Alternative Workplace Guidance Limit

(Long-term Exposure) ppm Excursion Limit (Short-term Exposure) ppm Refrigerant Concentration Limit (RCL) ppm a
Ethane 1,000 b (ACGIH TLV) 3,000 c (30-min ACGIH Excursion Limit) 2,900 d (15-min TEEL-1) 7,000

Propane 1,000 e (OSHA PEL/NIOSH REL) 10,000 f,g (10-min AEGL-1) 6,900 f (30-min AEGL-1) 5,300
An explanation of each exposure limit and exposure- limit related terminology is described in Table 5.

a ASHRAE (2010b)
b ACGIH (2012)

c Calculated as three times the TLV-TWA. (ACGIH 2004)
d DOE (2008)

e OSHA PEL available at: http://www.cdc.gov/Niosh/np g/npgd0524.html
f An IDLH of 2,100 ppm has been established for propa ne. However, NIOSH (1996) states that "[b]ased on acute inhalation toxicity data in humans (ACGIH 1991; Braker 1980), a value much grea ter than 10,000 ppm would have been appropriate. Ho wever, the revised IDLH for propane is 2,100 ppm based strictly on safety consi derations (i.e., being 10% of the lower explosive l imit of 2.1%)." Therefore, as this IDLH value is based on flammability concerns and not toxicity concerns, it is not used in the evaluation of toxic ity risks in this risk screen.

g AEGL-1 available at: http://www.epa.gov/opptintr/a egl/pubs/results96.htm

Table 5. Explanation of Exposure Limit-Related Term inology a Organization Definition OSHA Occupational Safety and Health Administration NIOSH National Institute for Occupational Safety and Heal th ACGIH American Conference of Governmental Industrial Hygi enists AIHA American Industrial Hygiene Association Exposure Limit Definition Explanation Short

- Term Exposure STEL Short

- Term Exposure Limit A 15

- minute TWA exposure that should not be exceeded at any time during a workday, even if the 8-hour TWA is wi thin the TLV– TWA, set by ACGIH.

AEGL b,c Acute Exposure Guideline Level 1 AEGL

- 1 is the airborne concentration (expressed as ppm or mg/m 3 ) of a substance above which it is predicted that the general population, including susceptible individuals, coul d experience notable discomfort, irritation, or certain asymptom atic nonsensory

12 It should be noted that this risk screen evaluates both short-term occupational and end-use (i.e., no n-occupational) exposure for ethane by comparison to the excursion limit, which is typically used to evaluate short-term occupation al exposure. EPA believes, however, that in the absence of an AEGL, STEL, or E RPG, the excursion limits provides a reasonable pro xy. Notably, the ACGIH methodology (i.e., a calculation of three times the TLV-TWA) has also been used by DOE (2008) to devel op a temporary emergency exposure limit for ethane (3,500 mg/m 3 or 2,900 ppm 15-min TWA), which applies to the gen eral population.March 29, 2016 – Final 7 effects. However, 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 o r mg/m 3 ) of a substance above which it is predicted that the general population, including susceptible individuals, coul d experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape. Acute Exposure Guideline Level 3 AEGL

- 3 is the airborne concentration (expressed as ppm o r mg/m 3 ) of a substance above which it is predicted that the general population, including susceptible individuals, coul d experience lifethreatening health effects or death.

ERPG Emergency Response Planning

Guideline 1 The maximum airborne concentration below which it i s believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient health effec ts or perceiving a clearly defined, objectionable odor according to AI HA. Emergency Response Planning Guideline 2 The maximum airborne concentration below which it i s believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other se rious health effects or symptoms which could impair an individua l's ability to take protective action according to AIHA. Emergency Response Planning Guideline 3 The maximum airborne concentration below which it i s 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

- chain alkane gases through butane) does not have a TLV-short-term exposure lim it, an excursion limit may be applied. Excursions in worke r exposure levels may exceed 3 times the TLV-TWA for no more t han a total of 30 minutes during a workday, and under no circumsta nces should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded according to ACGIH. IDLH Immediately Dangerous to Life and

Health If exposed to this concentration, room occupants ar e expected to be able to escape the room within 30 minutes withou t experiencing escape-impairing or irreversible health effects.

TEEL e Temporary Emergency Exposure

Limit 1 TEEL

- 1 is the maximum concentration in air below which i t is believed nearly all individuals could be exposed wi thout experiencing other than mild transient adverse heal th effects or perceiving a clearly defined, objectionable odor. Temporary Emergency Exposure Limit 2 TEEL

- 2 is the maximum concentration in air below which i t is believed nearly all individuals could be exposed wi thout experiencing or developing irreversible or other se rious health effects or symptoms that could impair their abiliti es to take protective action. Temporary Emergency Exposure Limit 3 TEEL

- 3 is the maximum concentration in air below which i t is believed nearly all individuals could be exposed wi thout experiencing or developing life-threatening health effects. RCL Refrigerant Concentration Limit The RCL for a refrigerant is intended to reduce the risks of acute toxicity, asphyxiation, and flammability hazards in normallyMarch 29, 2016 – Final 8 occupied, enclosed spaces. The RCL for each refrige rant is the lowest of the Acute-Toxicity Exposure Limit (ATEL), Oxygen Deprivation Limit (ODL), and Flammable Concentratio n Limit (FCL). Determination assumes full vaporization with no rem oval by ventilation, dissolution, reaction, or decompositio n and complete mixing of refrigerant in the space to which it is r eleased. 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 near ly all workers may be repeatedly exposed, day after day, for a wor king 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 Applicable to emergency exposure periods ranging fr om 10 minutes to 8 hours.
d ACGIH (2004)

e Chemical exposure guidelines to use for emergency planning if no AEGL or ERPG is available. TEELs are developed based on concentration limits or toxicology parameters (DOE 2008). According to the respective SDS for ethane and prop ane, exposure to ethane or propane may be hazardous if inhalation, skin contact, or eye contact with th e proposed substitutes occurs. The most likely path way of exposure is through inhalation. Ethane and propane can cause symptoms of asphyxiation when present in concentrations high enough to significantly lower o xygen concentrations below 19.5 percent by volume, such as headaches, ringing in ears, dizziness, drow siness, nausea, vomiting, depression of all senses, and also unconsciousness. Under some circumstances of o ver-exposure (i.e., oxygen levels fall below 6 perc ent by volume), death may occur. If ethane or propane is inhaled, person(s) should b e immediately removed from the contaminated space a nd exposed to fresh air. In accordance with the SDS, E PA further recommends that if breathing is difficul t or irregular, person(s) should be given oxygen, provid ed a qualified operator is present, and medical att ention be sought. Exposures of ethane or propane to the sk in may cause frostbite. In the case of dermal expos ure, the SDS for ethane and propane recommends that pers on(s) immediately wash the affected area with water and remove all contaminated clothing; if frostbite occurs, bathe (not rub) the affected area with luke warm, not hot, water. If water is not available, cover th e affected area with a clean, soft cloth, and seek medical attention immediately. Exposures of ethane or propa ne to the eyes could cause eye irritation. In case of ocular exposure, the SDS for ethane and propane rec ommends that person(s) immediately flush the eyes, including under the eyelids, with copious amounts o f water for 15 minutes. EPA’s review of the human health impacts of the pro posed substitutes is contained in the public docket for this decision. The potential health effects of ethane and propane can be minimized by following the exposure guidelines and ventilation and PPE recomme ndations outlined in the SDS for ethane and propane and this risk screen.



### 7. FLAMMABILITY ASSESSMENT ASHRAE Standard 34 classifies ethane and propane as Class A3 refrigerants. Ethane is flammable when it s concentration in the air is in the range of between 3.0 percent and 12.5 percent by volume (30,000 ppm to 125,000 ppm) and propane is flammable when its conc entration in air is in the range of 2.1 percent to 9.5 percent by volume (21,000 ppm to 95,000 ppm). In th e presence of an ignition source (e.g., static electricity, a spark resulting from a switch malfun ction, or a cigarette), an explosion or a fire coul d occur when the concentration of ethane or propane exceeds their respective lower flammability limits (LFL) o f 30,000 ppm or 21,000 ppm, posing a significant safe ty concern for workers and personnel if they are no tMarch 29, 2016 – Final 9 handled carefully. Only refrigerant technicians cer tified to work with flammable refrigerants should h andle VLT units containing ethane and propane during manu facturing, installation, servicing, and disposal. T he remainder of this section assesses the flammability risks and summarizes the recommended measures to ensure safe handling and use of the refrigerant dur ing servicing, disposal, and end-use.

7.1 Flammability Risk during Manufacture In production facilities or other facilities where large quantities of the refrigerant will be stored, proper safety precautions should be in place to minimize t he risk of explosion. As indicated by the submitter , the proposed substitute is purchased by a third-party s upplier and not manufactured on site. However, Eppendorf manufactures the very low temperature fre ezers and, during the final stage of freezer manufacture, the two refrigerant stages are filled with the proposed substitutes. [ ] Any release of r efrigerant is expected to take place during this filling activ ity which is assumed to occur in a factory area wit h proper ventilation rates. All ethane and propane storage and transport equipm ent should be installed with safety devices that minimize the likelihood of catastrophic releases. V LT freezers installed with ethane and propane shoul d be clearly labeled as containing a flammable refrigera nt. EPA believes that because relevant safety stand ards, the SDS for ethane and propane, and OSHA requiremen ts under 29 CFR 1910 (e.g., proper ventilation and storage practices within manufacturing facilities t o prevent fire and explosion) are followed by worke rs, flammability during manufacture is not a concern. 7.2 Flammability Risk during Servicing and End-Use The risk of flammability during servicing and end-u se for the reasonable worst-case scenario (see Sect ion 5) was investigated for ethane and propane. Both servi cing and end-use of VLT freezers charged with ethan e and propane are expected to take place in the same location. During servicing, the proposed substitute is expected to be recovered using recovery equipment d esigned specifically for flammable hydrocarbon refrigerants (i.e., equipped with flammable gas lea k detectors and monitors and without potential sour ces of ignition) with sufficient onboard storage capacity and suitable for the refrigerant in terms of the pr essure rating and compatibility of valve seals (GIZ 2010).

The submitter indicates that the substitutes will b e recovered using approved recovery equipment and t he amount released during recovery operation will be a fraction of a gram (Eppendorf 2015). In order to determine the potential flammability risks during s ervicing or end-use in case of a catastrophic relea se of refrigerant in the laboratory module, concentration s of ethane and propane immediately following a complete release of both refrigerants, were compare d to the lower flammability limit (LFL) for ethane (30,000 ppm) and propane (21,000 ppm). Table 6 pres ents the results of the analysis. Table 6. Flammability Assessment a

Scenario Substitute Charge Size (g) Effective Room

Size (m 3 ) Maximum Instantaneous

Concentration (ppm) b,c

Reasonable Worst-Case 1 Ethane 98 28 (1,000 ft 3 ) 2,800 Propane* 120 17,800

Reasonable Worst-Case 2 Ethane 150 28 (1,000 ft 3 ) 4,280 Propane* 150 22,200
Threshold Analysis 1: Charge Size Ethane 142 28 (1,000 ft 3 ) 4,040 Propane* 142 21,000
Threshold Analysis 2a: Room Size Ethane* 98 24 (840 ft 3 ) 3,300 Propane* 120 21,000
Threshold Analysis 2b: Room Size Ethane 150 30 (1,050 ft 3 ) 4,040 Propane* 150 21,000March 29, 2016 – Final 10 Bold font indicates modeling results. *Vertical concentration gradient is assumed.

a Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options.
b Lower Flammability Limits for ethane and propane a re equal to 30,000 ppm and 21,000 ppm, respectively

. c Values provided in these columns refer to the conce ntration in entire room because a vertical concentr ation gradient is not assumed. In this scenario, 100% of the charge size leaks. The air fl ow rate is 4 ACH.
d Because ethane and propane have different LFLs, th e threshold analyses were based on the propane conc entration reaching the LFL (i.e., 21,000 ppm). As demonstrated in Table 6, the maximum instantaneo us concentrations of ethane and propane in the enti re room at the typical charge sizes (i.e., 98 grams of ethane and 120 grams of propane) would be approximately 2,800 ppm and 17,800 ppm, respectivel y. At the maximum charge size (i.e., 150 grams of each refrigerant), the maximum instantaneous concen trations of ethane and propane in the room would be approximately 4,280 ppm and 22,200 ppm, respectivel y (Reasonable Worst-Case Scenario 2). Under Reasonable Worst-Case Scenario 2, the maximum insta ntaneous concentration of ethane is significantly below the LFL for ethane, while the modeled concent ration for propane is slightly greater (approximate ly 6 percent) than the LFL for propane. However, the est imated exposures were derived using conservative assumptions, and represent a worst-case scenario wi th a low probability of occurrence, as the analysis assumes the minimum required laboratory ventilation rate and does not consider opened windows, fans operating, or other variables that would reduce the concentration levels in the air. Therefore, under the reasonable worst-case scenarios, ethane and propane are not expected to present a significant risk of flammability. Given these results, it is not expect ed that propane used in a single refrigeration loop in this end-use will present a significant risk of flammabi lity. EPA also performed threshold analyses to determine the minimum room size in which a VLT freezer should be installed for flammability to not be of c oncern. Because ethane and propane have different L FLs, the threshold analyses were based on the propane co ncentration reaching the LFL (i.e., 21,000 ppm), wh ich is the more conservative value.

• The results of Threshold Analysis 1 indicate that f or flammability to be of concern within an effective room size of 28 m 3 , the total charge size should be at least 284 gram s (or 142 grams per refrigerant circuit).

• As shown in Threshold Analyses 2a and 2b, an indivi dual VLT freezer with typical charge sizes (98 grams of ethane and 120 grams of propane) and maxim um charge sizes (150 grams of both ethane and propane) should not be placed in a room smaller than 24 m 3 (840 ft 3 ) or 30 m 3 (1,050 ft 3 ), respectively. Although the results of Threshold Analysis 1 equate to individual circuit charge sizes less than the maximum allowable charge size and the results of Th reshold Analysis 2b equates to a room size larger t han that in the reasonable worst-case scenario, the res ults were derived using conservative assumptions as mentioned above. Furthermore, it is extremely unlik ely that the entire charge of both refrigerant circ uits would accidentally and simultaneously release into the space. [ ] EPA recommends that warning labels are present on t he equipment indicating that flammable refrigerants are inside the unit as well as notifying the user t o read the equipment use instructions which provide safety guidelines for handling propane. Therefore, these g uidelines should be acknowledged and followed to mitigate flammability risk. The installation of lea k prevention devices would further protect against the very limited risk of explosion. EPA also recognizes that multiple VLT freezers may be used in one room as the submitter states that anywhere from one to two units to hundreds of VLT f reezers are likely to be installed side-by-side in laboratories and other proposed end-use locations. However, a scenario in which more than one unit lea ks simultaneously is extremely unlikely and therefore does not pose any additional flammability risk. ASHRAE Standard 34 also more conservatively recomme nds that the RCLs for ethane (8.7 g/m 3 or 7,000 ppm by volume) and propane (9.5 g/m 3 or 5,300 ppm by volume) should not be exceeded. Th us, EPAMarch 29, 2016 – Final 11 believes that when VLT freezer units are installed in spaces that are consistent with manufacturer recommendations and the guidelines of relevant safe ty standards (e.g., ASHRAE 15 and 34), flammability risk is not a significant concern. End-users, howev er, should still ensure that there is adequate spac e (i.e., the effective volume of the room should be larger t han 24 m 3 or 30 m 3 ), depending on the charge size of the VLT freezer (see Table 6) and ventilation in any ro om where the VLT freezers are installed to mitigate the risk of fire or explosion resulting from a catastro phic leak during end-use or servicing activities. Catastrophic releases of large quantities of refrig erant, especially in areas where refrigerant is sto red, could lead to an explosion in the presence of an ignition source. For this reason, it is important that only properly trained and certified technicians handle ethane and propane. As a further precaution, certification requirements and training programs for technicians that handle ethane and propane should be developed using these guidelines. During servicing operation s, technicians should ensure that proper ventilatio n is in place through the use of fans (or other mechanical ventilation devices) and portable refrigerant detec tors should be used to alert technicians to the presence of flammable gases in the area. In addition, VLT f reezers installed with ethane and propane should be clearly labeled as containing flammable refrigerants. Beca use relevant safety standards and the SDS for ethane an d propane are followed by service technicians and because these refrigeration units will be installed in areas with adequate space and ventilation, EPA believes that flammability during servicing and end-use is n ot expected to be of concern.



### 8. ASPHYXIATION ASSESSMENT The risk of asphyxiation for the reasonable worst-c ase scenarios described in Section 5 were investiga ted for ethane and propane. In this section, risk of as phyxiation is assessed in three ways: 1) modeling the oxygen concentration under the char ge size and room size specified in the worstcase scenario, 2) performing a threshold analysis of minimum charg e size at which an asphyxiation risk could occur in the room size specified in the worst-case scenario (i.e., charge sizes greater than this are expected to cause an asphyxiation risk), and 3) performing a threshold analysis of the maximum r oom size at which an asphyxiation risk could occur with the charge size specified in the worst-c ase scenario (i.e., room sizes smaller than this ar e expected to cause an asphyxiation risk). This analysis does not consider ventilation or cond itions that are likely to occur that would increase oxygen levels to which individuals would be exposed, such as open doors or windows, fans operating, condition ed airflow (either heated or cooled), or even openings at the bottom of doors that allow air to flow in a nd out. As specified in Section 5, the reasonable worst-cas e scenario assumes a vertical concentration gradien t. If the proposed substitute passes the screening analys is with these restrictive assumptions in place, it can be reasonably assumed that no risks of asphyxiation wi ll be present under real-world conditions. The resu lts of the asphyxiation assessment are summarized in Table 7 below. Table 7. Asphyxiation Assessment a

Scenario Substitute Charge Size (g) Effective Room

Size (m 3 ) Percent Oxygen

Concentration in Room b

Reasonable Worst-Case Ethane 98 28 (1,000 ft 3 ) 20 Propane 120

Reasonable Worst-Case Ethane 150 28 (1,000 ft 3 ) 20 Propane 150
Threshold Analysis 1: Charge Size Ethane 1,100 28 (1,000 ft 3 ) 12 Propane 1,940March 29, 2016 – Final 12 Threshold Analysis 2a: Room Size Ethane 98 0.34 (12 ft 3 ) 12 Propane 120
Threshold Analysis 2b: Room Size Ethane 150 0.48 (17 ft 3 ) 12 Propane 150
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 concentration of oxygen in air is cons idered to be 21 percent (Mackenzie & Mackenzie 1995 ). In order for a risk of asphyxiation to occur, the n ormal concentration of oxygen in air (21 percent) m ust be reduced to 12 percent. 13 Based on the worst-case scenario modeling assumpti ons, ethane and propane in a VLT freezer have an insignificant impact on the con centration of oxygen in the air and therefore do no t present a significant risk of asphyxiation. Given t hese results, it is expected that propane used in a single refrigeration loop in this end-use will also presen t an insignificant risk of asphyxiation. This model ing does not take into account any ventilation which is like ly to occur, such as conditioned airflow, open door s, or even openings at the bottom of doors that allow air to flow in and out, as mentioned above; therefore, the actual asphyxiation risk to personnel is likely to be even smaller than modeled. For the asphyxiation threshold analyses shown in Ta ble 7, the conditions at which an asphyxiation conc ern would exist were determined.

• As shown under Threshold Analysis 1, the charge siz es of ethane and propane in a VLT freezer in a 28 m 3 room would have to be at least 1,100 grams and 1,9 40 grams, respectively, for asphyxiation to be a concern, which is more than seven times gre ater than the maximum charge size proposed by UL (i.e., 150 grams).

• Using the typical charge sizes of 98 grams and 120 grams for ethane and propane, respectively, as shown under Threshold Analysis 2a, the volume of th e room would have to be approximately 0.34

m 3 (12 ft 3 ), or approximately 80 times smaller than the model ed laboratory volume for asphyxiation to be of concern.

• Using the charge size of 150 grams for both ethane and propane, as shown under Threshold Analysis 2b, the volume of the room would have to b e approximately 0.48 m 3 (17 ft 3 ), or approximately 58 times smaller than the modeled lab oratory volume for asphyxiation to be of

concern. The space where a VLT freezer containing ethane and propane is installed must allow for adequate room for end-users to access the machine. To further prevent risk of asphyxiation, end-users should ensure that there is adequate space accounting for other appliances, furniture, or storage (i.e., the effective volume o f the room should be larger than 0.35 m 3 or 0.48 m 3 , depending on the charge size of the refrigeration unit [see Table 7]) and ventilation (in accordance with the S DS for ethane and propane) in any room where the VL T freezers are installed. Additionally, adherence to ASHRAE 34, which provides more conservative concentration limits, will ensure that asphyxiation is not a risk. Minimum room sizes according to the RCL stated in ASHRAE 34 can be found in Section 6. Beca use VLT freezers are unlikely to be installed in spaces where full release of ethane and propane wou ld displace enough oxygen to cause asphyxiation, EP A does not believe that the use of ethane and propane in VLT freezers with either the typical or maximum charge sizes poses a significant risk of asphyxiati on or impaired coordination to laboratory personnel

.


### 9. END-USE EXPOSURE ASSESSMENT This section presents estimates of potential person nel exposures to ethane and propane during use of V LT freezers. Personnel exposure analysis was performed to determine acute/short-term laboratory personnel exposures resulting from potential catastrophic lea kage of refrigerant from VLT freezers. The analysis was undertaken to determine the 30-minute TWAs for etha ne and propane, which were compared to the 30-min

13 Twelve percent oxygen in air is the No Observed Adv erse Effect Level (NOAEL) for hypoxia (ICF 1997).March 29, 2016 – Final 13 Excursion Limit for ethane and STEL for propane. Th e results of the end-use exposure assessment are presented in Table 8 to assess the risk to personne l. The estimated exposures were derived using conservative assumptions, and represent a worst-cas e scenario with a low probability of occurrence, as the analysis assumes the minimum required laboratory ve ntilation rate and does not consider opened windows
, fans operating, or other variables that would reduc e the levels to which individuals would be exposed. Table 8. End-Use Exposure Assessment a

Scenario Substitute Charge Size (g) Effective Room

Size (m 3 ) 30-min TWA End-Use

Exposure (ppm) b,c

Reasonable Worst-Case 1 Ethane 98 28 (1,000 ft 3 ) 1,570 Propane* 120 2,560

Reasonable Worst-Case 2 Ethane 150 28 (1,000 ft 3 ) 2,400 Propane* 150 3,200
Threshold Analysis 1: Charge Size Ethane 187 28 (1,000 ft 3 ) 3,000 Propane* 187 4,000
Threshold Analysis 2a: Room Size Ethane 98 10 (360 ft 3 ) 4,200 Propane* 120 6,900
Threshold Analysis 2b: Room Size Ethane 150 22 (790 ft 3 ) 3,000 Propane* 150 4,000 *Vertical concentration gradient is assumed. Bold font indicates modeling results.

a Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling a ssumption options.
b See Table 4 for more information.

c The limiting factor in each threshold analysis sce nario was assumed to be the most conservative compo nent (e.g., greatest charge size in Threshold Analysis 2a and lowest exposure limit in Threshold Analysis 2b).

Under the reasonable worst-case scenario described in Section 5, catastrophic releases of ethane and propane from a VLT freezer with typical charge size s (98 grams of ethane and 120 grams of propane) and maximum charge sizes (150 grams of both ethane and propane) were modeled. The modeling indicates that the maximum anticipated personnel exposure concentr ation at the maximum charge sizes for ethane and propane are 2,400 ppm and 3,200 ppm, respectively, which are below the 30-min Excursion Limit of 3,000 ppm for ethane and the STEL of 6,900 ppm for propan e. The maximum anticipated personnel exposure concentration at the typical charge sizes (98 grams of ethane and 120 grams of propane) are also well below the 30-minute Excursion Limit and STEL for ethane a nd propane, respectively (see Table 8). Given these results, it is expected that propane used in a sing le refrigeration loop in this end-use will also not present a significant personnel exposure risk at end-use. A threshold analysis was performed to determine the charge size and room volume where VLT freezers containing ethane and propane could be installed to avoid the short-term exposure limit for each refri gerant. Based on Threshold Analysis 1 shown in Table 8 and assuming the limiting factor is the lower exposure limit of ethane, the maximum charge size that shoul d be installed in a room of 28 m 3 (1,000 ft 3 ) volume is 374 grams (i.e., 187 grams per refrigerant circuit) . Additionally, an individual VLT freezer with typi cal charge sizes (98 grams of ethane and 120 grams of p ropane) and maximum charge sizes (150 grams of both ethane and propane) should not be placed in a room smaller than 10 m 3 (360 ft 3 ) or 22 m 3 (790 ft 3 ), respectively. Because the modeling was done using a conservative laboratory module size, personnel exposure to the proposed substitute at end-use is n ot considered a significant risk. To mitigate risk during end-use, EPA recommends that for a minimum room vol ume of 28 m 3 , the charge size not exceed 285 grams for either ethane or propane refrigerant circ uit, and for a maximum charge size of 150 grams eac h, the VLT freezer not be installed in a room of volum e less than 15 m 3 (520 ft 3 ). To minimize the risk of exposure, EPA recommends th at refrigeration units be installed in rooms withMarch 29, 2016 – Final 14 adequate space and/or the ventilation and engineeri ng control (e.g., local ventilation such as a fan o r vents on doors to adjoining rooms) outlined in the SDS fo r ethane and propane. To prevent exposure and poten tial serious side effects during larger releases, EPA re commends that the charge size for an ethane and pro pane VLT freezer does not exceed the RCL for either refr igerant (7,000 ppm for ethane and 5,300 for propane ) and proposes to require compliance with UL 471. Pro per leak protection devices and engineering control requirements and adherence to the SDS will further ensure that exposure limits are maintained below th ose described in Table 8.



### 10. OCCUPATIONAL EXPOSURE ASSESSMENT This section assesses potential exposures to worker s during manufacture, installation, servicing, and disposal of propane and ethane. As indicated by the submitter and discussed in Section 5.1, the propos ed substitute is purchased and not manufactured on sit e. The charging of ethane and propane VLT freezer u nits occurs at the final stage of freezer manufacture. T o ensure that use of the proposed substitutes in VL T freezers does not pose an unacceptable risk to work ers during servicing and disposal, occupational exp osure modeling was performed using a box-model approach. For a detailed description of the methodology used for this screening assessment, the reader is referr ed the occupational exposure and hazard analysis de scribed in Chapter 5 of the Background Document. The modele d exposure concentrations were compared to shortterm occupational exposure limits at servicing and long-term exposure limits at disposal. The sections below describe the occupational exposure assessment s conducted for the manufacture, servicing, and disposal of ethane and propane VLT freezers.

10.1 Occupational Exposure during Manufacture As indicated by the submitter, the proposed substit ute is purchased by a third-party supplier and not manufactured on site. Ethane and propane are produc ed around the world, including in the United States
, and are used in a wide variety of refrigerant and n on-refrigerant uses. During manufacture of ethane a nd propane, the SDS should be referenced and proper en gineering controls and PPE used. Ethane and propane are not expected to pose a risk to workers during m anufacture when the engineering controls and PPE recommendations referenced in the SDS for ethane an d propane are followed. Engineering controls should include high local ventilation (e.g., chemical hood s) for standard manufacturing procedures so workers can avoid physical contact with the refrigerant and to achieve emission control. Occupational exposure to ethane and propane may occ ur during VLT freezer manufacturing. During manufacture, points of refrigerant release would be from connection/disconnection of temporary lines f or charging and recovery equipment. However, charging is controlled and occurs in the manufacturing facil ity equipped with automatic ventilation, refrigerant de tectors, and alarm systems. Furthermore, only train ed technicians will be handling the hydrocarbon refrig erants and specialized charging equipment. [ ] The submitter estimates the magnitude of release to be limited to less than one gram of refrigerant per refrigeration circuit (Eppendorf 2015). EPA believes that when proper handling and disposal guidelines are followed in accordance with both go od industrial hygiene and manufacturing practices and the SDS for ethane and propane, there is no signifi cant risk to workers during the manufacture of ethane an d propane.

10.2 Occupational Exposure during Servicing During servicing, ethane and propane refrigerants f rom the VLT freezer are removed using recovery equipment designed for hydrocarbon refrigerants and pumped into a canister, where they are stored unti l repairs are made before the system is refilled. Iso lation and evacuation of lines or equipment prior t o servicing or repair and the use of compatible seals , gaskets, O-rings, thread sealants, and minimizati on of threaded joints all contribute to limiting releases . Room ventilation, leak monitors, and alarms also minimize exposure.March 29, 2016 – Final 15 Servicing activities for VLT freezers are not expec ted to result in significant worker exposure when certified technicians follow the procedures outline d in the ethane and propane SDS and maintenance manual, undergo proper training, and wear appropria te PPE (e.g., gloves, safety glasses). Nevertheless , the potential occupational exposure during servicing wa s analyzed. The release rate per servicing event wa s multiplied by the number of events estimated to occ ur over a workday. For the VLT freezer end-use, the release per event was conservatively assumed to be 0.25 percent of the equipment charge during servici ng. It was conservatively assumed that eight events of servicing a unit by one servicing technician occur in an 8-hour work day. The maximum 30-minute TWA exposures for ethane and propane were estimated and compared to their respective STELs (see Table 9). The modeling result s indicate that the maximum anticipated occupationa l exposure concentrations at no point exceed the STEL for ethane or propane.

Table 9. Occupational Risk Assessment during Servic ing a
Component 30-minute TWA Occupational Exposure (ppm) Short Term Exposure Limits (ppm) Charge Size: Typical Charge Size: Maximum Ethane 0. 67 1.0 3,000 b Propane 0. 56 0.70 6,900 c Bold font indicates modeling results.

a Cells highlighted in green are the scenarios that are deemed to be acceptable given various modeling assumption options.
b Calculated as three times the TLV-TWA. ACGIH (2004 )

c 30-minute AEGL-1; see Table 4 for more information
The modeling results indicate that the maximum anti cipated occupational exposure concentrations are ve ry low with the typical charge sizes (98 grams of etha ne and 120 grams of propane) and maximum charge sizes (150 grams of both ethane and propane). Occup ational exposure concentrations during servicing fr om the use of propane in a single refrigeration loop a re expected to be even lower. Further, the estimate d exposures were derived using conservative assumptio ns, and represent a worst-case scenario with a low probability of occurrence. To further mitigate potential exposures during serv icing operations, technicians should ensure that pr oper ventilation is in place through the use of fans (or other mechanical ventilation devices) and portable refrigerant detectors should be used to alert techn icians to the presence of flammable gases in the ar ea. If a technician is servicing a bank of VLT freezer units charged with ethane and propane and venting occurs frequently, EPA recommends the use of this safety e quipment to prevent the concentration of ethane in the room from exceeding its RCL.

10.3 Occupational Exposure during Disposal According to the submitter, at disposal of the VLT freezer, the proposed substitutes will be recovered using approved recovery equipment into a cylinder, labele d accordingly, and returned to a disposal location where the refrigerants can be recycled or combusted (Eppe ndorf 2015). Disposal of VLT freezers is expected t o occur with limited frequency at disposal facilities and with limited duration of exposure to the refri gerant charge. Typically, potential exposures to the refri gerants during recovery and disposal are expected t o occur during activities related to decommissioning refrig eration systems (e.g., attaching of hoses associate d with draining or otherwise discharging of refrigerant fr om the refrigeration units into cylinders) and woul d be similar to those during servicing, because similar refrigerant charging and/or recovery equipment woul d be used (see Section 10.2 and Table 9 for information and modeling results related to exposure during servicing activities). For disposal, it was conservatively assumed that 10 units are disposed of during an 8-hour work day; however, it was assumed that of the 10 units, only the last unit per workday would experience a catast rophic release of refrigerant (i.e., 100 percent of the eq uipment charge). The remaining 9 units were assumed to release an incidental amount of refrigerant (i.e., 1 percent per unit) from the connecting and disconn ectingMarch 29, 2016 – Final 16 of lines, as it is likely that if a worker was expo sed to the entire charge of a system during disposa l activities, they would immediately stop working, cl ear the area until all refrigerant has been removed from the space (e.g., through ventilation), and adhere t o the exposure procedures recommended in the SDS fo r the proposed substitutes (see Section 10.3). Table 10 displays the maximum estimated 8-hour TWA occupational exposure levels for ethane and propane during disposal. Because modeled exposure l evels for both the typical charge sizes (98 grams o f ethane and 120 grams of propane) and maximum charge sizes (150 grams of both ethane and propane) are significantly lower than the 8-hour exposure limits for ethane and propane, occupational exposure to t he proposed substitute during disposal is not consider ed a toxicity risk. Occupational exposure concentra tions during disposal from the use of propane in a single refrigeration loop are expected to be even lower. Further, estimated exposures were derived using con servative assumptions (e.g., no ventilation) and represent a worst-case scenario with a low probabil ity of occurrence. These types of systems are typic ally disposed of by trained personnel using proper indus trial hygiene techniques while wearing PPE. Furthermore, it is highly unlikely that a facility would be decommissioning 10 VLT freezers containing ethane and propane consecutively, considering the s pecialized nature of this equipment. A more realist ic scenario might consider the disposal of one ethane and propane VLT freezer among the disposal of sever al domestic refrigerators and freezers containing othe r refrigerants. Nonetheless, the estimated exposure s for the worst-case scenario are not considered to be si gnificant.

Table 10. Occupational Risk Assessment during Dispo sal a
Component 8

- hour TWA Occupational Exposure (ppm) 8-Hour Long Term Exposure Limits (ppm) Charge Size: Typical Charge Size: Maximum Ethane 55 85 1,000 b Propane 46 58 1,000 c Bold font indicates modeling results.

a Cells highlighted in green are the scenarios that are deemed to be acceptable given various modeling assumption options.
b ACGIH (2012)

c OSHA PEL and NIOSH REL
Although anticipated occupational exposures are wel l below the exposure limits for ethane and propane, the recommendations for proper engineering controls and PPE in the SDS for ethane and propane should be followed. Adequate ventilation should always be est ablished during any use, handling, or storage of et hane and propane. Engineering controls should include va por-in air detection systems and local exhaust ventilation during use of ethane and propane to pre vent dispersion of the proposed substitute througho ut the work place. EPA believes that if proper handling an d disposal guidelines are followed in accordance wi th good industrial hygiene and manufacturing practices and the SDS for ethane and propane, there is no significant risk to workers during the disposal of ethane and propane in VLT freezers.



### 11. GENERAL POPULATION EXPOSURE This section presents an assessment of potential ri sks to the general population posed by the use of e thane and propane in VLT freezers. The general population is defined in this risk screen as non-personnel wh o are subject to exposure of the proposed substitute near industrial facilities, including manufacturing or equipment production factories, equipment operating sites (for on-site installation or disposal activi ties only), or recycling centers, rather than consumers at end-use. General population exposures to ambient air, surfac e water and solid waste to releases of ethane and propane are not expected when manufactured for use and used as a refrigerant in VLT freezers. The proposed substitutes are proposed for use in separa te refrigerant circuits that are hermetically seale d. Thus, significant releases are not anticipated. At room t emperature, ethane and propane are gases and, there fore, releases to ground or surface water are not anticip ated, as ethane and propane are anticipated to diss ipate into the atmosphere upon release to outside air (i. e., because natural ventilation rates would be high er and there is no enclosed space to keep ethane or propan e concentrated). Should air releases duringMarch 29, 2016 – Final 17 manufacturing operations occur, engineering control s should be used (e.g. carbon absorption scrubbers) to collect ethane and propane and prevent any releases to the atmosphere. EPA believes that by using prop er engineering controls and by following disposal and containment recommendations outlined in the propose d substitute’s SDS, exposure to ethane and propane is not expected to pose a significant toxicity risk t o the general population.March 29, 2016 – Final 18 

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