March 28, 2016 – Final 1 

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

Risk Screen on Substitutes in Chillers and Cold Sto rage Warehouses

Substitute: Propylene (R-1270)

This risk screen does not contain Clean Air Act (CA A) Confidential Business Information

(CBI) and, therefore, may be disclosed to the publi c.



### 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 h as already screened a large number of substitutes in m any end-uses and applications within all of the maj or ODS-using sectors including: refrigeration and air conditioning; solvent cleaning; foam blowing; aeros ols; fire suppression; adhesives, coatings and inks; and sterilization. The results of these risk screens a re presented 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 propylene (R-1270) a s a substitute in the chillers and cold storage war ehouse end-uses. Table 1 presents the composition of the p roposed substitute.

Table 1. Composition of Propylene and Potential Im purities

Constituent Chemical Formula CAS Number Concentration (Weight Percent) Propylene (R-1270) C 3 H 6 115-07-1 >99.5 Potential Impurities

Hexane C 6 H 14 110-54-3 <0.005 Water H 2 O 7732-18-5 <0.0025 Butadiene C 4 H 6 106-99-0 <0.0005 Sulfur S 7704-34-9 <0.0002 Benzene C 6 H 6 71-43-2 <0.0001 Residue NA NA <0.005 Acid NA NA <0.000002 Other a NA NA <0.5
NA - Not available

a The composition of “Other” impurities was not speci fied by the submitter.March 28, 2016 – Final 2 Section 2 summarizes the results of the risk screen for the proposed substitute listed in Table 1. Th e remainder of the risk screen is organized into the following sections:

• Section 3: Atmospheric Assessment

• Section 4: Volatile Organic Compound Assessment

• Section 5: Potential Health Effects

• Section 6: Flammability Assessment

• Section 7: Occupational Exposure Assessment

• Section 8: General Population Exposure Assessment

• Section 9: References



### 2. SUMMARY OF RESULTS Propylene is not recommended for SNAP approval as a refrigerant in chillers or cold storage warehouses due to its potential impacts on local air quality r elative to available substitutes in these end-uses. Propylene is regulated as a volatile organic compou nd (VOC) under CAA regulations (40 CFR 51.100(s)). Based on analysis of potential impacts of hydrocarb on refrigerant emissions on ground-level ozone concentrations, VOCs from the use of propylene are anticipated to result in greater impacts on local a ir quality in the United States than other available o ptions. According to the results of the assessments in this risk screen, significant flammability and toxicity risks are likely for chillers and cold storage systems (s ee Sections 6 and 7 of this document). Exposure dur ing end-use is captured in the occupational exposure as sessment (see Section 7 of this document), as consu mer use of chillers and cold storage equipment is not a nticipated. In addition, potential health risks fro m exposure to the proposed substitute is considered t o be a larger concern for workers, due to the large spaces in which chillers and cold storage equipment are installed and serviced. Therefore, an asphyxia tion assessment was not conducted.



### 3. ATMOSPHERIC ASSESSMENT This section presents an assessment of the potentia l risks to atmospheric integrity posed by the use o f propylene in chillers and cold storage warehouses. 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 harmf ul to the ozone layer, has lower climate impact, an d a shorter ALT when compared to refrigerants such as C FC-12, HCFC-22, and R-502. In addition, propylene also has lower climate impact and a shorter ALT tha n those predicted for other substitutes examined in the Background Document as well as commonly utilized re frigerants HFC-134a, R-407C, and R-404A.March 28, 2016 – Final 3 Table 2. Atmospheric Impacts of Propylene Compared to Other Refrigerants Used in Chillers and Cold Storage Warehouses
Refrigerant Ozone Depleting Potential (ODP) a Global Warming Potential (GWP) b Atmospheric Lifetime in Years (ALT) b Propylene 0 1.8 0.35 days a CFC

- 12 0.82 10,900 100 R

- 502 c 0.2 4,650 NA d HCFC

- 22 0.13 1,810 12 HFC

- 134a 0 1,430 14 R

- 407C e 0 1,774 NA f R

- 404A g 0 3,922 NA h NA - Not applicable

a World Meteorological Organization (WMO) 2010 Scient ific Assessment Report (2011)
b Intergovernmental Panel on Climate Change (IPCC) 4 th Assessment Report (Forster et al. 2007)

c R-502 is a blend consisting of HCFC-22 (49%) and CF C-115 (51%).
d Atmospheric lifetimes are not given for blends, be cause the components separate in the atmosphere. Th e 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]).

e R-407C is a blend consisting of HFC-32 (29%), HFC- 125 (25%) and HFC-134a (52%).
f Atmospheric lifetimes are not given for blends, be cause the components separate in the atmosphere. Th e ALT for HFC-32 is 4.9 years, the ALT for HFC-125 is 29 years, and the ALT for HFC-134a i s 14 years (IPCC 4 th Assessment Report [Forster et al. 2007]).

g R-404A is a blend consisting of HFC-143a (52%), HF C-125 (44%) and HFC-134a (4%).
h Atmospheric lifetimes are not given for blends, be cause the components separate in the atmosphere. Th e ALT for HFC-143a is 52 years, the ALT for HFC-125 is 29 years, and the ALT for HFC-13 4a is 14 years (IPCC 4 th Assessment Report [Forster et al. 2007]).


### 4. VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS Propylene is regulated as a VOC under CAA regulatio ns (40 CFR 51.100 [s]). Emissions of propylene should be controlled according to CAA and other reg ulations by adhering to standard industry practices

. EPA prepared a separate analysis in 2014 1 and a follow-on analysis in 2016 2 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 under different scenarios. The hydrocarbo n emissions from these scenarios were estimated based on EPA’s Vintaging Model, and their potential contributions to ozone concentrations were assessed using EPA’s Community Multiscale Air Quality (CMAQ) model. 3 CMAQ modeling was performed for April through the e nd of September, as these months presented the largest releases of hydrocarbo n refrigerant as well as weather conditions favorab le for ozone formation. The ozone concentrations were estimated for the Atlanta, Houston, and Los Angeles regions, due to their distinctive geographic settin g and chronic high levels of ground-level ozone, an d then scaled for national emission estimates. The analysis considers the propensity of organic co mpounds to form ozone according to their maximum incremental reactivity (MIR). The MIR scale assesse s a compound’s contributions to the photochemical ozone formation in urban plumes and is reflective o f its use in North America, where ground-level ozon e formation is considered an urban issue. Table 3 lis ts the MIR for several compounds, including the hydrocarbons examined in this analysis.

1 Assessment of the Potential Impact of Hydrocarbon R efrigerants on Ground-Level Ozone Concentrations (February 2014) [EPAHQ-OAR-2013-0748-0003]
2 Follow-on Assessment of the Potential Impact of Hyd rocarbon Refrigerants on Ground Level Ozone Concent rations (March 2016)
3 VM version VM_IO file_v4.4_10.13.14 and CMAQ model version 5.0.2 were used in this analysis.March 28, 2016 – Final 4 Table 3. Propensity of Refrigerants to Form Troposp heric Ozone

Compound North America MIR Scale (g-O 3 /g-substance) HCFC-22 <0.1
HFC-134a <0.1 Propylene 11.57
Ethane a 0.28
Isobutane 1.34 Propane 0.56 Source: IPCC (2005)

a EPA uses the reactivity of ethane as the threshold for determining whether a compound has negligible reactivity. Compounds that are less reactive than, or equally reactive to, ethane under certain assume d conditions may be deemed negligibly reactive and th erefore suitable for exemption from the definition of a VOC (EPA 2012a). As demonstrated in Table 3, propylene’s MIR is more than 20 times greater than the MIR for propane, an d approximately 9 times greater than the MIR for isob utane. Therefore, propylene is significantly more likely to form tropospheric ozone than other refrig erants examined in this analysis. These analyses estimated hydrocarbon refrigerant em issions in 2030 (EPA 2014) and 2040 (EPA 2016) from different scenarios and compared their resulti ng relative increases in ozone concentrations again st the National Ambient Air Quality Standard (NAAQS) for o zone of 70 ppb. 4 All three regions examined in these analyses (i.e., Los Angeles, Atlanta and Hous ton) are forecast to be in attainment of the 2015 8 -hr 70 ppb ozone standard by 2040. Isobutane, a less reactive hydrocarbon than propyle ne, was modeled in all refrigeration and air conditioning equipment. The results of this scenari o indicate there could be an incremental increase u p to 0.72 ppb in 2030. In the alternative case, which as sumed 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 6.6 ppb o zone in 2030 (EPA 2014) or 7.8 ppb ozone in 2040. Although potential impacts from isobutane were only modeled in 2030, the relative impact of isobutane in 2040 is still anticipated to be significantly less than that of propylene, because isobutane is signif icantly less reactive. EPA performed an additional analysis to determine r efrigerant emissions resulting from the use of propylene in a limited number of refrigeration and air conditioning end-uses including chillers, cold storage warehouses, and certain residential and lig ht commercial air conditioning applications and the ir potential contributions to tropospheric ozone gener ation. Emissions from these select end-uses were estimated to result in an incremental maximum incre ase of the 8-hour average of up to 4.5 ppb in 2040. In addition, EPA examined a more realistic scenario in which refrigerant emissions from propylene and R443A, a hydrocarbon refrigerant blend containing ap proximately 55 percent propylene, were modeled in cold storage warehouses, residential and light comm ercial air conditioning, and large commercial air conditioning applications including chillers, as we ll as refrigerant emissions from R-441A and propane in room air conditioners. Refrigerant emissions from t his scenario resulted in an incremental maximum increase of the 8-hour average of 2.6 ppb in 2040. The increase in ozone is estimated to be about 95 percent associated with the use of propylene as a r efrigerant, including its use as a component of R-4 43A, and 4 percent from propane, including its use as a component of R-443A and R-441A, under this scenario

. The results of the CMAQ modeling are summarized in Table 4.

4 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 28, 2016 – Final 5 Table 4. Estimated Maximum Increase in the Daily 8- hour Ground-Level Ozone in 2040 from Hydrocarbon Refrigerant Emissions

Equipment Refrigerant 8-hr Ozone Maximum Change (ppb) All refrigeration and air conditioning equipment Propylene 7.8
Isobutane 0.72 a
Chillers, cold storage warehouses, and certain residential and light commercial air conditioning applications Propylene 4.5 Propane, Propylene, R

- 441A, R-443A 2.6 b

a The 8-hr maximum increase in ground-level ozone is observed in 2030 for the isobutane scenario.
b 95 percent of the change in ozone is associated wit h the use of propylene as a refrigerant and as a component of R-443A, and 4 percent from propane as a refrigerant and as a component of R-441A and R443A, under this scenario.
Although most ozone nonattainment areas are not VOC -limited (i.e., the formation of ozone in these are as is not by limited by VOC emissions, but by other co mpounds such as nitrogen oxides [NO x ]), allowing the use of propylene in chillers and cold storage facil ities could introduce VOC loading that would place a further burden on reaching attainment and extend th e timeline for compliance for some areas.
Furthermore, substitutes such as ammonia, R-450A, a nd R-513A are approved in these end-uses and contain only compounds exempt from the definition o f VOC. Because propylene is highly reactive, VOC emissions from the use of propylene in chillers and cold storage warehouses are anticipated to contrib ute to ground-level ozone concentrations in the United Sta tes significantly more than less reactive hydrocarb ons and other available options for these end-uses. The refore, propylene is not recommended for SNAP approval as a refrigerant in chillers or cold stora ge warehouses.



### 5. POTENTIAL HEALTH EFFECTS To assess potential health risks from exposure to t he proposed substitute in chillers and cold storage warehouses, EPA identified the relevant toxicity th reshold values for comparison to modeled exposure concentrations for different scenarios. According t o American Society of Heating, Refrigerating, and A irConditioning Engineers (ASHRAE) Standard 34, propyl ene is listed under safety group A3 with a refrigerant concentration limit ( RCL) of 1,000 ppm (ASHRAE 2013b). ASHRAE 34 RCLs ar e intended to reduce the risks of acute toxicity, asphyxiation, a nd flammability hazards in normally occupied, enclo sed spaces during refrigerant use and protect end-users from the potential dangers of a catastrophic leak from a refrigeration unit (ASHRAE 2013b). 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 2013a). As such, this risk screen references the RCL for propylene in addition to the lower flam mability limit (LFL), hypoxia no observed adverse effect level (NOAEL), and exposure limits, as an ad ditional, conservative limit to ensure that signifi cant flammability, asphyxiation, and occupational exposu re risks, respectively, do not occur. For the occupational exposure analysis, potential r isks from chronic and acute worker exposure were evaluated by comparing exposure concentrations with available occupational exposure limits. Potential risks of chronic worker exposure were evaluated usi ng workplace guidance levels (WGL). Risks from potential short-term consumer exposures were evalua ted by comparing exposure concentrations with emergency guidance levels. In the absence of an est ablished short-term exposure limit (STEL), acute exposure guideline (AEGL), or emergency response pl anning guideline (ERPG), potential short-term, occupational exposures were compared with an excurs ion limit, which was calculated according to theMarch 28, 2016 – Final 6 methodology described by the American Conference of Governmental Industrial Hygienists (ACGIH) (2004). 5 Table 5 lists the relevant toxicity limits of prop ylene and its potential impurities and is followed by Table 6, which provides an explanation of each t oxicity limit. EPA’s approach for identifying or developing these values is discussed in Chapter 3 o f the Background Document.

Table 5. Exposure Limits of Propylene

Component WGL

(Long-term Exposure) ppm EGL

(Short-term Exposure) ppm IDLH

(Short-term Exposure) ppm Refrigerant

Concentration Limit (RCL) ppm Propylene 500 (ACGIH-TLV) 1,500 (30-min ACGIH Excursion Limit) a NA 1,000 b
Potential Impurities Hexane 50 (ACGIH-TLV) c 150 (15-min STEL) c 1,100 c,d NA Butadiene 1 (OSHA-PEL) e 5 (15-min STEL) e 2,000 e,f NA Benzene 1 (OSHA-PEL) g 5 (15-min STEL) g 500 g,h NA An explanation of each exposure limit and exposure- limit related terminology is described in Table 6.

a Calculated as three times the threshold limit value -time-weighted average (TLV-TWA) (ACGIH 2004).
b ASHRAE (2013b)

c The ACGIH-TLV, STEL, and IDLH for hexane are availa ble at: https://www.osha.gov/dts/chemicalsampling/data/CH_2 45400.html

. d Although an RCL is not available for hexane, the Im mediately Dangerous to Life or Health (IDLH) concen tration of 1,100 ppm is most similar to the Acute-Toxicity Exposure Limit (ATEL) , which is an RCL intended to reduce the risks of a cute toxicity hazards in normally occupied, enclosed spaces.

e The permissible exposure limit ( PEL), STEL, and IDLH for butadiene are available at : https://www.osha.gov/dts/chemicalsampling/data/CH_2 22100.html

. f Although an RCL is not available for butadiene, th e IDLH concentration of 2,000 ppm is most similar t o the ATEL, which is an RCL intended to reduce the risks of acute toxicity haza rds in normally occupied, enclosed spaces.

g The PEL, STEL, and IDLH for benzene are available a t: https://www.osha.gov/dts/chemicalsampling/data/CH_2 20100.html

. h Although an RCL is not available for benzene, the I DLH concentration of 500 ppm is most similar to the ATEL, which is an RCL intended to reduce the risks of acute toxicity hazards in no rmally occupied, enclosed spaces.

Table 6. Explanation of Exposure Limit-Related Term inology a Organization Definition OSHA Occupational Safety and Health Administration NIOSH National Institute for Occupational Safety and Health ACGIH American Conference of Governmental Industrial Hygi enists OARS Occupational Alliance for Risk Science Exposure Limit Definition Explanation Short

- Term Exposure RCL Refrigerant Concentration

Limit The RCL for a refrigerant is intended to reduce the risks o f acute toxicity, asphyxiation, and flammability hazards in normally occupied, enclosed spaces. The RCL for each refrigerant is the lowest of the ATEL, Oxygen Deprivation Limit (ODL), and Flammable Concentratio n Limit (FCL). Determination assumes full vaporization with no rem oval by ventilation, dissolution, reaction, or decomposition and complet e mixing of refrigerant in the space to which it is released.

5 It should be noted that this risk screen evaluates short-term occupational exposure to propylene by c omparison to the excursion limit, which is typically used to evaluate short-te rm occupational exposure. EPA believes that, in the absence of an AEGL, STEL, or ERPG, the excursion limit provides a reasonable proxy. Notably, the ACGIH methodology (i.e., using three times the TLVTWA) has also been used by the Department of Energy (DOE) (2008) to develop a temporary emergency expo sure limit for propylene (2,500 mg/m 3 or 1,500 ppm 15-min TWA), which applies to the gen eral population.March 28, 2016 – Final 7 ATEL Acute Toxicity Exposure Limit The ATEL is t he refrigerant concentration limit intended to r educe the risks of acute toxicity hazards in normally occupie d, enclosed spaces according to ASHRAE Standard 34. The ATEL includes consideration of mortality, cardiac sensitization, anesthetic or cen tral nervous system effects and other escape impairing effects and perm anent injury. The ATEL is similar to the IDLH concentrations set by N IOSH. STEL Short

- Term Exposure Limit A 15

- minute TWA exposure that should not be exceeded dur ing a workday, even if the 8-hour TWA is within the TLV–T WA, set by ACGIH. ACGIH Excursion Limits b Short

- Term Exposure Limit Because methane and other short

- chai n alkane gases through butane do not have a TLV-STEL, an excursion limit may be a pplied. Excursions in worker exposure levels may exceed 3 times the TL V-TWA for no more than a total of 30 minutes during a workday, and un der no circumstances should they exceed 5 times the TLV-TWA, provided th at the TLV-TWA is not exceeded according to ACGIH. I DLH Immediately Dangerous to

Life or Health If exposed to this concentration, room occupants ar e expected to be able to escape the room within 30 minutes without experi encing escapeimpairing or irreversible health effects. Long

- Term Exposure PEL Permissible Exposure Limit This is an 8

- hour TWA exposure limit set by OSHA. AEL Acceptable Exposure Limit T he maximum 8

- hour TWA at which a worker can be exposed regularly without adverse effects. WEEL Workplace Environmental

Exposure Level Developed by OARS for to protect healthy workers ag ainst acute and chronic health effects, this limit is based on repe ated daily exposures over a working lifetime and averaged over an 8-hour workday. TLV

- TWA Threshold Limit Value

– Time

Weighted Average T he 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 li fetime without adverse effect according to ACGIH.

a All information in this table taken from EPA (1994) except where otherwise noted.
b ACGIH (2004) According to the safety data sheet (SDS), exposure to propylene may be hazardous if inhalation, skin contact, or eye contact with the proposed substitut e occurs. The most likely pathway of exposure is through inhalation. Propylene 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, vom iting, depression of all senses, and also unconsciousness. Under some circumstances of over-e xposure (i.e., oxygen levels fall below 6 percent b y volume), death may occur. If propylene is inhaled, person(s) should be immedi ately removed from the contaminated space and 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 propylene to the skin may c ause frostbite. In the case of dermal exposure, the SDS for propylene recommends that person(s) immediately wash 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, and seek medical attentio n immediately. Exposures of propylene to the eyes cou ld cause eye irritation. In case of ocular exposure , the SDS for propylene recommends that person(s) immedia tely 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 pr oposed substitute is contained in the public docket for this decision. The potential health effects of propylene can be mi nimized by following the exposureMarch 28, 2016 – Final 8 guidelines and ventilation and personal protective equipment (PPE) recommendations outlined in the SDS for propylene and this risk screen.



### 6. FLAMMABILITY ASSESSMENT ASHRAE Standard 34 classifies propylene as an A3 re frigerant. Propylene is flammable when its concentration in air is in the range of 2.0 percent to 11.1 percent by volume (20,000 ppm to 111,000 p pm). In the presence of an ignition source (e.g., static electricity or a cigarette), an explosion or a fir e could occur if the concentration of propylene were to exc eed the LFL of 20,000 ppm. The remainder of this section addresses flammability risks and summarizes the recommended measures to ensure safe handling and use of the refrigerant during manufacture and s ervicing.

6.1 Flammability Risk at Equipment Manufacture The submitter intends to manufacture packaged propy lene chillers and cold storage units that are facto rybuilt and installed on-site. Thus, release of or ex posure to propylene may be possible at the charging and sealing steps at the manufacturing site. It is ther efore important that all relevant standards be foll owed during the manufacture of propylene refrigeration u nits. EPA recommends that engineering controls should include normal and local ventilation (e.g., chemical hoods) for standard manufacturing procedur es so workers can avoid physical contact with the refr igerant and to limit emissions. In general, use of appropriate PPE consistent with the Occupational Sa fety and Hazard Administration’s (OSHA’s) guidelines is recommended, such as splash goggles, mechanically-resistant gloves when handling cylinders, chemically-resistant gloves (e.g., butyl rubber, chlorinated polyethylene, or neoprene) whe n handling the gas mixture, and protective clothing. All propylene storage and transport equipment shoul d be installed with safety devices that minimize th e likelihood of catastrophic releases. For example, t he National Fire Protection Association (NFPA) 58 Liquefied Petroleum Gas Code (NFPA 2007) for liquef ied propylene requires the use of overfill protecti on devices (OPD) on cylinders to minimize the likeliho od of leaks. The NPFA 58 Code also contains propylene storage and transportation requirements/g uidelines. It is expected that refrigerants be prop erly stored and caution used within manufacturing facili ties to minimize explosion risk and that workers ad here to the requirements set by OSHA under 29 CFR 1910. OSHA requirements include proper ventilation and storage practices within manufacturing facilities t o prevent fire and explosion. Good manufacturing practices should be adhered to during the manufactu re of equipment containing propylene, e.g., using proper ventilation.

6.2 Flammability Risk at Servicing The risk of flammability during servicing was inves tigated for propylene. To represent the reasonable worst-case scenario for the proposed and typical ch arge sizes for positive displacement chillers and c old storage units (i.e., 12, 315 kg respectively) and t he typical charge size for centrifugal chillers (i. e., 930 kg), 6 it is assumed that a catastrophic leak of refriger ant occurs while the unit is serviced at end-use (i .e., rooftop of a commercial building). The average refr igerant concentration in the closest proximity to t he emission source following a catastrophic release wa s modeled using the box-model approach, which is described in Chapter 5 of the Background Document. This approach has been widely used for many years to estimate probable exposures of workers to hazard ous airborne materials, and has been described in

6 EPA’s Vintaging Model (VM_IO file_v4.4_10.13.14) mo dels three types of positive displacement chillers: screw, scroll, and reciprocating, with average charge sizes of 300 kil ograms, 240 kilograms, and 315 kilograms, respectiv ely, and centrifugal chillers with charge sizes ranging from 700 kilograms to app roximately 930 kilograms. This risk screen models t he largest of the typical charge sizes for each chiller type (i.e., 315 kilo grams for reciprocating chillers and 930 kilograms for centrifugal chillers).March 28, 2016 – Final 9 detail by the National Institute for Occupational S afety and Health (NIOSH). This model takes into consideration the duration and magnitude of the res ulting exposure which is influenced by the followin g: 1) Duration and intensity of the release, 2) Rate at which contaminated air is diluted with u ncontaminated air, 3) Proximity of the worker to the source of the rel ease, and 4) Length of time the worker remains in the affecte d space. In order to determine the potential flammability ri sks during servicing in case of a catastrophic rele ase of refrigerant, modeled concentrations of propylene im mediately following the release of refrigerant were compared with the LFL for propylene (20,000 ppm). The results of the flammability assessment are presented in Table 7.

Table 7 . Flammability Assessment a

Scenario Equipment Charge Size (kg) Maximum

Instantaneous Concentration (ppm) b Reasonable Worst

- Case Scenario 1 Proposed Chillers and Cold Storage 12 8,200 Reasonable Worst

- Case Scenario 2 Positive Displacement Chillers 315 215,300 Reasonable Worst

- Case Scenario 3 Centrifugal Chillers 930 635,600 Threshold Analysis 1 All Chillers and Cold Storage 29 20,000 Bold font indicates modeling results.

a Cells highlighted in green are the scenarios with a cceptable exposure levels given various modeling as sumption options.
b LFL of propylene is 20,000 ppm.
As demonstrated in Table 7, the maximum instantaneo us concentration does not exceed the LFL for propylene units with a 12-kilogram charge size, as proposed by the submitter. However, the maximum instantaneous concentration exceeds the LFL for pro pylene under Reasonable Worst-Case Scenarios 2 and 3 for the typical charge sizes of a positive displa cement chiller (i.e., 315 kilograms) and a centrifu gal chiller (i.e., 930 kilograms). The threshold condit ion at which a flammability concern would exist (i. e., when the maximum instantaneous concentration follow ing a complete release equals the LFL for propylene) was also determined. As shown under Thre shold Analysis 1, a flammability concern could occur if the charge size of a propylene chiller or cold storage unit is 29 grams or more, which is approximately 2.5 times greater than the charge siz e proposed by the submitter and approximately 11 ti mes smaller than the typical charge size for positive d isplacement chillers. Furthermore, positive displac ement and centrifugal chillers can have a wide variety of charge sizes, including as large as 10,000 kilogra ms. The catastrophic release of such a large system wou ld present an extremely significant flammability ri sk, resulting in exposures of approximately 300 times t he LFL for propylene (i.e., 6,830,000 ppm). For the proposed packaged positive displacement chi llers and cold storage systems, the submitter indic ates the units are equipped with an additional safety pa ckage that contains a hydrocarbon gas sensor, an evacuation fan, and explosion panels. If the sensor detects hydrocarbons at a concentration of 5 perce nt of the LFL (i.e., 1,000 ppm), the compressor and pump operation will shut down and the condenser fans wil l operate at full speed. In the case of an explosion, the explosion panels are designed to lift and guid e the substitute upwards towards the condenser fans which then completely ventilate the unit until it is man ually turned off (Frigadon AB 2015a). According to the submitter, warning labels are pres ent on the equipment indicating that flammable refrigerants are in use and that the user should re ad the equipment use instructions that provide safe ty guidelines for handling propylene in order to mitig ate flammability risk. The submitter also indicates leakMarch 28, 2016 – Final 10 prevention devices would be installed to further pr otect against the risk of explosion, and that only properly trained and certified technicians are expe cted to handle propylene (Frigadon AB 2015b).



### 7. OCCUPATIONAL EXPOSURE ASSESSMENT To ensure that use of the proposed substitute in ch illers and cold storage warehouses does not pose an unacceptable toxicity risk to workers during chargi ng, servicing, and disposal, occupational exposure modeling during charging at manufacture was perform ed for the proposed substitute. The methodology used for this screening assessment is described in Chapter 5 of the Background Document and Section 6. Although modeling is only performed for the system’ s initial charging, it is assumed that exposure dur ing servicing and disposal would not exceed exposure du ring charging because similar refrigerant charging and/or recovery equipment would be used. Furthermor e, because it is likely that less refrigerant remai ns in the unit at disposal, it is assumed that charging o f packaged chillers and cold storage equipment woul d require transfer of a greater amount of refrigerant , and result in greater worker exposure. Thus, occupational exposure was conservatively modeled ba sed on charging. The modeled scenario assumes a charge size for chil lers and cold storage equipment of 12 kilograms, as indicated by the submitter, along with more typical charge sizes of 315 kilograms for positive displacement chillers and 930 kilograms for centrif ugal chillers. Because these systems can have a var iety of charge sizes, including up to 10,000 kilograms, this maximum charge size was also modeled. Charging of chillers and cold storage equipment is expected to occur with limited frequency (up to approximatel y one event per day) and with limited duration of exp osure to the refrigerant charge. Release points dur ing charging would be connection/disconnection of tempo rary lines from charging equipment. The release per event was assumed to be 0.2 percent and 1 percent of the equipment charge for chillers and cold storage equipment, respectively. 7,8 The release per event was multiplied by the estima ted number of units charged over a workday. The maximum 30-minute TWA exposures for propylene was estimated for the charging scenario and compared to the short-ter m exposure limit for propylene (see Table 8).

Table 8. Occupational Risk Assessment at Charging for Propylene a

Equipment Charge Size (kg) 30-minute TWA Occupational

Exposure (ppm) 30-min Short Term Exposure Limit (ppm) b 0.2% Release 1% Release Proposed Chillers and Cold Storage 12 3 12
1,500 Positive Displacement Chillers 315 65 330 Centrifugal Chillers 930 190 960 All Chillers and Cold Storage 10,000 2,070 10,370 Bold font indicates modeling results.

a Cells highlighted in green are the scenarios that a re deemed to be acceptable given various modeling a ssumption options.
b EPA-derived STEL (see Table 5) Based on the assumptions described above, the model ing indicates that short-term (15-minute) worker exposure concentrations are not likely to exceed th e STEL (1,500 ppm) for propylene in the proposed an d typical charge sizes for chillers and cold storage equipment. However, worker exposure concentrations are

7 IPCC (2006) estimates that first-fill losses durin g installation of chillers can range from 0.2% to 1 %; DECC (2011) estimates first-fill losses for chillers is approximately 0.5 %; however, industry representatives indicate that the first-fill leak rate for chillers is lower than 0.5% (McQuay 2011). A proposed update to EPA’s Vintaging Model recommends a first-fill e missions rate of 0.2% from chillers manufactured after 1990.
8 IPCC (2006) estimates that first-fill losses during installation of cold storage warehouse systems can range from 0.5% to 3%; DECC (2011) estimates that first-fill losses for co ld storage units is approximately 1%; and, SKM Envi ros (2011) suggests that this loss rate should be less than 4%. A proposed u pdate to EPA’s Vintaging Model recommends a first-f ill emissions rate of 1% from cold storage units manufactured after 1990.March 28, 2016 – Final 11 likely to significantly exceed the STEL for propyle ne in larger chillers and cold storage units with a 10,000-kilogram charge size. Although these types o f systems are typically charged, maintained, and disposed by trained and EPA Section 608-certified r efrigerant technicians using proper industrial hygi ene techniques, propylene is still likely to present a toxicity risk during charging, servicing, and dispo sal when used in large chiller and cold storage systems.



### 8. GENERAL POPULATION EXPOSURE ASSESSMENT This section presents an assessment of potential ri sks to the general population posed by the use of propylene in chillers and cold storage warehouses. The general population is defined in this risk scre en as non-personnel who are subject to exposure of the pr oposed substitute near industrial facilities, inclu ding manufacturing or equipment production factories, eq uipment operating sites (for on-site installation o r disposal activities only), or recycling centers, ra ther than consumers at end-use. Propylene is not expected to cause a significant ri sk to human health in the general population when manufactured for use and used as a refrigerant in c hillers and cold storage warehouses. The proposed substitute will be manufactured in a closed process and is proposed for use in closed systems; thus, significant releases are not anticipated. At room t emperature, propylene is a gas; therefore, releases to ground or surface water are not anticipated, as pro pylene is anticipated to dissipate into the atmosph ere upon release to outside air (i.e., because natural ventilation rates would be higher and there is no e nclosed space to maintain a high concentration of propylene ). Should air releases during manufacturing operati ons occur, engineering controls should be used (e.g., c arbon absorption scrubbers) to collect propylene an d prevent the release of the chemical to the atmosphe re. EPA believes that by using proper engineering controls and by following disposal and containment recommendations outlined in the proposed substitute ’s SDS and this risk screen, exposure to propylene is not expected to pose a significant toxicity risk to the general population.March 28, 2016 – Final 12 

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