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Significant New Alternatives Policy Program 

Refrigeration and Air Conditioning Sector 

Risk Screen on Substitutes in Commercial Ice Machines 

Substitute: Propane (R-290) 

This risk screen is restricted to self-contained commercial ice makers meeting the requirements of 

UL 563. 

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

and, therefore, may be disclosed to the public. Brackets [ ] represent redacted CBI content. 

1. INTRODUCTION 

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

and legislative efforts that have taken place over the past two decades, including the Montreal Protocol and 

the Clean Air Act Amendments of 1990 (CAAA). The U.S. Environmental Protection Agency (EPA), as 

authorized by Section 612 of the CAAA, administers the Significant New Alternatives Policy (SNAP) 

Program, which identifies acceptable and unacceptable substitutes for ODS in specific end-uses based on 

assessment of their health and environmental impacts. 

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

potential human health and environmental risks posed by the substitute in specific applications. EPA has 

already screened a large number of substitutes in many end-uses and applications within all of the major 

ODS-using sectors including: refrigeration and air conditioning; solvent cleaning; foam blowing; aerosols; 

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

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

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

conditioning sector (EPA 1994) (hereinafter referred to as the Background Document). This risk screen 

evaluates the potential use of propane (R-290) as a substitute in the commercial ice machines end-use.

Table 1 presents the composition of the proposed substitute. 

Table 1. Composition of Propane and Potential Impurities 

Constituent Chemical Formula CAS Number Concentration

(Weight Percent)a

Propane (R-290) C3H8 74-98-6 >99.7%

Potential Impurities (Maximum Concentration)

Ethane C6H14 74-84-0 <0.17%

Propylene C3H6 115-07-1 <0.03%

n-Butane C4H10 106-97-8 <0.1%

Sulfur S 7704-34-9 <0.001%

Water H2O 7732-18-5 <0.0012%

Section 2 summarizes the results of the risk screen for the proposed substitute in Table 1. The remainder 

of the risk screen is organized into the following sections: 

• Section 3: Atmospheric Assessment 

• Section 4: Volatile Organic Compound Assessment 
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• Section 5: Discussion of End-Use Scenario 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 

Propane is recommended for SNAP approval for self-contained commercial ice machines that comply with 

Underwriters Laboratory (UL) Standard 563: Ice Makers. EPA's risk screen indicates that the use of the

proposed substitute will be less harmful to the atmosphere than the continued use of ODS and other 

commonly used refrigerants, as it is less harmful to the ozone layer, has lower climate impact, and a 

shorter atmospheric lifetime (ALT). 

Propane is regulated as a volatile organic compound (VOC) under CAA regulations (40 CFR 51.100(s)). 

Based on analysis of potential impacts of hydrocarbon refrigerant emissions on ground-level ozone 

concentrations, VOCs from the use of propane are not anticipated to result in greater impacts on local air 

quality in the United States than other available options. It is expected that the manufacturer’s safety data 

sheet (SDS) for propane and good manufacturing practices will be adhered to during handling or use of 

propane. Additionally, it is expected that the appropriate safety and personal protective equipment (PPE) 

(e.g., protective gloves, tightly sealed goggles, protective work clothing, and suitable respiratory protection 

in case of leakage or insufficient ventilation) consistent with Occupational Safety and Health 

Administration (OSHA) guidelines will be used during manufacture, installation and servicing, and 

disposal of commercial ice machines using propane. Because commercial ice machines are to be installed

in locations with adequate space and/or ventilation in accordance with EPA recommendations and the 

equipment maintenance manuals for propane, significant flammability, asphyxiation, or toxicity risk to

consumers is unlikely. 

Additional safeguards, including the refrigerant concentration limit (RCL) for propane, are provided in 

industry standards such as American Society of Heating, Refrigerating and Air-Conditioning Engineers 

(ASHRAE) Standards 15,1 34,2 and 623 and UL Standard 563: Ice Makers.4 

 

1 Safety Standard for Refrigeration Systems ASHRAE Standard 15 establishes safeguards for life, limb, health, and property and 

prescribes safety requirements. 

2 Designation and Safety Classification of Refrigerants ASHRAE Standard 34 is establishes a uniform system for assigning 

reference numbers, safety classifications, and refrigerant concentration limits to refrigerants. Safety classifications based on 

toxicity and flammability data are included. 

3 Ventilation for Acceptable Indoor Air Quality ASHRAE Standard 62 establishes minimum ventilation rates and other measures 

intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects. 

4 UL 563 Standard for Safety: Ice Makers establishes safety requirements for self-contained automatic ice makers employing 

hermetic refrigerant motor-compressors and air- or water-cooled condensers, and designed for connection to alternating-current 

circuits rated not greater than 600 volts (ANSI/UL 2013).
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3. ATMOSPHERIC ASSESSMENT 

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

propane in commercial ice machines. The ozone depletion potential (ODP), global warming potential 

(GWP), and ALT of the proposed substitute are presented in Table 2. 

The proposed substitute is substantially less harmful to the ozone layer, has lower climate impact, and a 

shorter ALT when compared to refrigerants such as CFC-12, R-502, and HCFC-22. In addition, propane 

has lower climate impact and a shorter ALT than those predicted for other substitutes examined in the 

Background Document as well as the commonly utilized refrigerants R-404A and HFC-134a. Thus, EPA 

believes that the use of propane would result in substantially less harm to the climate and ozone layer than 

the continued use of ODS and other commonly used refrigerants. 

Table 2. Atmospheric Impacts of Propane Compared to Other Refrigerants used in Commercial Ice 

Machines 

Refrigerant 

Ozone Depleting Potential

(ODP)a

Global Warming Potential

 (GWP)b

Atmospheric Lifetime in 

Years (ALT)b 

Propane 0

b 3.3 0.03a

CFC-12 0.82 10,900 100

R-502c 0.2 4,657 NAd

HCFC-22 0.13 1,810 12a

R-404Ae 0 3,922 NAf

HFC-134a 0 1,430 14

NA – Not applicable 

a World Meteorological Organization (WMO) 2010 Scientific Assessment Report (2011) 

b Intergovernmental Panel on Climate Change (IPCC) 4th Assessment Report (Forster et al. 2007) 

c R-502 is a blend consisting of HCFC-22 (49%) and CFC-115 (51%). 

d

 Atmospheric lifetimes are not given for blends, because the components separate in the atmosphere. The ALT for HCFC-22 is 12 years and 

the ALT for CFC-115 is 1,700 years (IPCC 4th Assessment Report [Forster et al. 2007]). 

e R-404A is a blend consisting of HFC-143a (52%), HFC-125 (44%) and HFC-134a (4%). 

f Atmospheric lifetimes are not given for blends, because the components separate in the atmosphere. The ALT for HFC-143a is 52 years, the 

ALT for HFC-125 is 29 years, and the ALT for HFC-134a is 14 years (IPCC 4th Assessment Report [Forster et al. 2007]). 

4. VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS 

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 regulations by adhering to standard industry practices. 

EPA prepared a separate analysis in 20145

 and a follow-on analysis in 20166 to evaluate the potential 

impact of the use of hydrocarbon refrigerants on ground-level ozone concentrations in the United States. 

These analyses estimated refrigerant emissions from refrigeration and air conditioning equipment, which 

were assumed to contain propylene, isobutane, and/or propane7 under different scenarios and compared 

their resulting relative increases in ozone concentrations against the National Ambient Air Quality 

 

5 Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level Ozone Concentrations (February 2014) [EPAHQ-OAR-2013-0748-0003] 

6 Follow-on Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level Ozone Concentrations (March 

2016)

7 EPA uses the maximum incremental reactivity (MIR) of ethane (0.28 g-O3/g-substance) as the threshold for determining whether 

a compound has negligible reactivity. Propylene (MIR = 11.57), isobutane (MIR = 1.34), and propane (MIR 0.56) are all 

considered to be reactive compounds and are therefore subject to VOC regulations.
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Standard (NAAQS) for ozone of 70 ppb.8 Under the most conservative scenario it was assumed that 

propylene was used in all refrigeration and air conditioning equipment. In more realistic scenarios, all 

three hydrocarbons (and/or blends thereof) were assumed to be used in certain types of refrigeration and 

air conditioning equipment, depending on the proposed use of each alternative under submissions received 

by the SNAP program at the time of the analysis. 

End-uses in the evaluation included a number of types of smaller, self-contained refrigeration (including 

commercial ice machines) and room air-conditioning units for which SNAP hydrocarbon applications have 

been received and/or UL Standards covering flammable refrigerants exist. The hydrocarbon 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.9 

CMAQ modeling was performed for April through the end of September, as these months presented the 

largest releases of hydrocarbon refrigerant as well as weather conditions favorable for ozone 

formation. The ozone concentrations were estimated for the Atlanta, Houston, and Los Angeles regions, 

due to their distinctive geographic setting and chronic high levels of ground-level ozone, and then scaled 

for national emission estimates. 

The results of the CMAQ modeling indicated that under the most conservative case which assumed that 

the most reactive hydrocarbon, propylene, was used in all refrigeration and air conditioning equipment, 

there could be an incremental maximum increase of the 8-hour average as high as 7.8 ppb ozone in 2040.

By comparison, the most realistic scenario, in which a mixture of hydrocarbon refrigerants are used, 

refrigerant 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 greatest ozone problem. 

This upper bound level of increase for the realistic scenario is not likely, as most ozone nonattainment 

areas are not VOC-limited (i.e., the formation of ozone in these areas is not limited by VOC emissions, but 

by other compounds such as nitrogen oxides [NOx]). In addition, the analysis assumed no use of VOCexempt refrigerants which will also likely be used in refrigeration and air conditioning end-uses along with 

hydrocarbon refrigerants. Based on the results of this analysis, VOC emissions from the use of propane in 

commercial ice machines are not anticipated to contribute significantly to ground level ozone 

concentrations in the United States. 

5. DISCUSSION OF END-USE SCENARIOS MODELED 

Propane has been proposed for the commercial ice machine end-use. The modeled end-use scenario 

assumes a charge size of 150 grams for commercial ice machines, as indicated by the submitter. The 

modeled charge size is also consistent with UL Standard 563: Ice Makers, which limits the charge size of 

ice machine refrigeration equipment for ASHRAE classified A3 refrigerants to 150 grams (UL 2015). 

Commercial ice machines can be installed in a wide range of locations with varying room volumes (e.g.,

hotels, bars, and restaurants). To represent the reasonable worst-case scenario for commercial ice 

machines, it is assumed that a catastrophic leak of refrigerant occurs while an ice machine is installed at 

end-use (i.e., restaurant kitchen). Based on the room sizes provided by the submitter, the analysis in this 

risk screen assumes that the ice machine is located in a restaurant kitchen with a height of 2.4 meters (7.8 

 

8 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).

9 VM version VM_IO file_v4.4_10.13.14 and CMAQ model version 5.0.2 were used in this analysis.
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feet), a minimum effective volume of 22 m3 (780 ft3), or a typical effective volume of 120 m3 (4,240 ft3) 

(i.e., excluding the space filled by the ice machine, shelving, other kitchen equipment, etc.). 

Under this reasonable worst-case scenario, the full charge of the unit is assumed to be emitted over the 

course of one minute into the restaurant kitchen with 20 air changes per hour (ACH).10 A vertical 

concentration gradient is also assumed in the worst-case scenario since propane is denser than air (specific 

gravity of propane relative to air is 1.52 [air = 1]) and will settle in higher concentrations closer to the 

ground. In order to simulate the vertical concentration gradient of refrigerant following release, it is 

assumed that 95 percent of the leaked refrigerant mixes evenly into the bottom 0.4 meters (1.3 feet) of the 

room, and the rest of the refrigerant mixes evenly in the remaining volume (Kataoka 2000). Table 3 details 

the end-use modeling assumptions used throughout the risk screen (i.e., in Sections 7, 8 and 9). 

Table 3. End-Use Scenario Model Assumptions 

Parameter Assumptions

Room Restaurant Kitchen

Charge Size (g) 150a

Length of Release (minutes) 1 

Room Size (volume - m3) 22 (780 ft3); 120 (4,240 ft3)

b

Room Ventilation (air changes per hour) 20c

Vertical Concentration Gradient Yes

a UL 563 maximum charge size for ice makers using Class A3 refrigerants. 

b Manitowoc (2015) 

c The typical ventilation rate for a commercial kitchen is 20 to 40 air changes per hour (McMullan 2014). 

EPA recognizes that commercial ice machines may be placed in a variety of locations with different room 

sizes and ventilation rates. There may also be instances in which the consumer chooses to place an ice

machine and other pieces of equipment (e.g., a vending machine) within an enclosed space (thus further

limiting the effective volume of the space), or a single ice machine in a very small enclosed space. When 

units are installed in smaller, enclosed spaces, there is a higher risk for asphyxiation or exposure concerns. 

To address this variability in room volumes and charge sizes for installed ice machines, this risk screen 

incorporates threshold analyses in addition to the worst-case scenario modeling. The threshold analyses are 

performed in order to determine the room size and charge size requirements that ensure that the use of

propane in commercial ice machines does not present risk to end-users or servicing technicians. 

6. POTENTIAL HEALTH EFFECTS 

To assess potential health risks from exposure to the proposed substitute in commercial ice machines, EPA 

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

different scenarios. According to ASHRAE Standard 34, propane is listed under safety group A3 with a 

RCL of 5,300 ppm (ASHRAE 2013a). ASHRAE 34 RCLs are intended to reduce the risks of acute 

toxicity, asphyxiation, and flammability hazards in normally occupied, enclosed spaces during refrigerant 

use and protect end-users from the potential dangers of a catastrophic leak from a refrigeration unit 

(ASHRAE 2013a). ASHRAE Standard 15 implements the aforementioned standard, requiring that “the 

concentration of refrigerant in an enclosed space following a complete discharge of a high-probability

system shall not exceed the RCL” (ASHRAE 2013b). As such, this risk screen references the RCL for 

propane in addition to the lower flammability limit (LFL), hypoxia no observed adverse effect level 

 

10 The air exchange rate for a commercial kitchen is derived from the suggested sufficient ventilation in commercial kitchens of 20 

to 40 air changes per hour (McMullan 2014).
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(NOAEL) and exposure limits, as an additional, conservative limit to ensure that significant flammability, 

asphyxiation, and end-use exposure risks, respectively, do not occur. 

For the occupational exposure analysis, potential risks from chronic and acute worker exposure were 

evaluated by comparing exposure concentrations with available occupational exposure limits. Potential 

risks of chronic worker exposure were evaluated using workplace guidance levels (WGL). Risks from 

potential short-term consumer exposures were evaluated by comparing exposure concentrations to 

emergency guidance levels (EGL). In the absence of an established short-term exposure limit (STEL), 

acute exposure guideline level (AEGL), or emergency response planning guideline (ERPG), potential 

short-term, end-use exposures were evaluated. Table 4 lists the relevant toxicity limits and RCL of propane 

and is followed by Table 5, which provides an explanation of each toxicity limit. EPA’s approach for 

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

Table 4. Exposure Limits of Propane 

Component 

WGL

(Long-term Exposure) 

ppm 

EGL

(Short-term Exposure) 

Ppm 

Refrigerant Concentration 

Limit (RCL) 

ppm 

Propane 1,000a 

(OSHA PEL/NIOSH REL) 

10,000b,c (10-min AEGL-1)

6,900c (30-min AEGL-1) 5,300d

Potential Impurities

Ethane 1,000e (ACGIH TLV) 3,000f

(30-min ACGIH Excursion Limit)

2,900g (15-min TEEL-1) 7,000d

Propylene 500e (ACGIH TLV) 1,500f (30-min ACGIH Excursion Limit) 1,000d

n-Butane 1,000e (ACGIH TLV) 6,900h (30-min AEGL-1) 4,000d

An explanation of each exposure limit and exposure-limit related terminology is described in Table 5. 

a

 OSHA PEL available at: http://www.cdc.gov/Niosh/npg/npgd0524.html 

b An IDLH of 2,100 ppm has been established for propane. However, NIOSH (1996) states that "[b]ased on acute inhalation toxicity data in 

humans (ACGIH 1991; Braker 1980), a value much greater than 10,000 ppm would have been appropriate. However, the revised IDLH for 

propane is 2,100 ppm based strictly on safety considerations (i.e., being 10% of the lower explosive limit of 2.1%)." Therefore, as this IDLH 

value is based on flammability concerns and not toxicity concerns, it is not used in the evaluation of toxicity risks in this risk screen. 

c

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

d ASHRAE (2010b) 

e

 ACGIH TLV for aliphatic hydrocarbon gases: alkane (C1 - C4) is 1,000 ppm TWA (ACGIH 2012) 

f Calculated as three times the TLV-TWA (ACGIH 2004).

g Department of Energy (DOE) (2008) 

h AEGL-1 available at: http://www.epa.gov/oppt/aegl/pubs/rest102.htm

Table 5. Explanation of Exposure Limit-Related Terminologya 

Organization Definition

OSHA Occupational Safety and Health Administration

NIOSH National Institute for Occupational Safety and Health

ACGIH American Conference of Governmental Industrial Hygienists

AIHA American Industrial Hygiene Association

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 of acute toxicity, 

asphyxiation, and flammability hazards in normally occupied, enclosed 

spaces. The RCL for each refrigerant is the lowest of the Acute-Toxicity 

Exposure Limit (ATEL), Oxygen Deprivation Limit (ODL), and Flammable 

Concentration Limit (FCL). Determination assumes full vaporization with 
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no removal by ventilation, dissolution, reaction, or decomposition and 

complete mixing of refrigerant in the space to which it is released. 

STEL Short-Term Exposure Limit A 15-minute TWA exposure that should not be exceeded during a 

workday, even if the 8-hour TWA is within the TLV–TWA, set by ACGIH. 

AEGLb,c 

Acute Exposure Guideline 

Level 1 

AEGL-1 is the airborne concentration (expressed as ppm or mg/m3) of a 

substance above which it is predicted that the general population, 

including susceptible individuals, could experience notable discomfort, 

irritation, or certain asymptomatic nonsensory 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 or mg/m3) of a 

substance above which it is predicted that the general population, 

including susceptible individuals, could experience irreversible or other 

serious, long-lasting adverse health effects or an impaired ability to 

escape. 

Acute Exposure Guideline 

Level 3 

AEGL-3 is the airborne concentration (expressed as ppm or mg/m3) of a 

substance above which it is predicted that the general population, 

including susceptible individuals, could experience life-threatening health 

effects or death. 

TEELd

Temporary Emergency 

Exposure Limit 1 

TEEL-1 is the maximum concentration in air below which it is believed 

nearly all individuals could be exposed without experiencing other than 

mild transient adverse health effects or perceiving a clearly defined, 

objectionable odor. 

Temporary Emergency 

Exposure Limit 2 

TEEL-2 is the maximum concentration in air below which it is believed 

nearly all individuals could be exposed without experiencing or 

developing irreversible or other serious health effects or symptoms that 

could impair their abilities to take protective action. 

Temporary Emergency 

Exposure Limit 3 

TEEL-3 is the maximum concentration in air below which it is believed 

nearly all individuals could be exposed without experiencing or 

developing life-threatening health effects. 

Long-Term Exposure

PEL Permissible Exposure Limit This is an 8-hour TWA exposure limit set by OSHA. 

RELe Recommended Exposure 

Limit 

This is an 8-hour TWA recommended by NIOSH.

TLV-TWA Threshold Limit Value –TimeWeighted Average The TWA concentration for a conventional 8-hour workday and a 40-

hour workweek, to which it is believed that nearly all workers may be 

repeatedly exposed, day after day, for a working lifetime without adverse 

effect according to ACGIH. 

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

b EPA (2012) 

c Applicable to emergency exposure periods ranging from 10 minutes to 8 hours. 

d DOE (2008) 

e

 NIOSH (2015) 

According to the SDS, exposure to propane may be hazardous if inhalation, skin contact, or eye contact

with the proposed substitute occurs. The most likely pathway of exposure is through inhalation. Propane 

can cause symptoms of asphyxiation when present in concentrations high enough to significantly lower 

oxygen concentrations below 19.5 percent by volume, such as headaches, ringing in ears, dizziness, 

drowsiness, nausea, vomiting, depression of all senses, and also unconsciousness. Under some 

circumstances of over-exposure (i.e., oxygen levels fall below 6 percent by volume), death may occur. In 

addition, at high concentrations, propane can act as a narcotic and cause central nervous system 

depression, including dizziness, drowsiness, and headaches. 
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If propane is inhaled, person(s) should be immediately removed from the contaminated space and exposed

to fresh air. In accordance with the SDS, EPA further recommends that if breathing is difficult or irregular, 

person(s) should be given oxygen, provided a qualified operator is present, and medical attention be 

sought. Exposures of propane to the skin may cause frostbite. In the case of dermal exposure, the SDS for 

propane 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 attention 

immediately. Exposures of propane to the eyes could cause eye irritation. In case of ocular exposure, the 

SDS for propane recommends that person(s) immediately flush the eyes, including under the eyelids, with 

copious amounts of water for 15 minutes. 

EPA’s review of the human health impacts of this proposed substitute is contained in the public docket for 

this decision. The potential health effects of propane can be minimized by following the exposure 

guidelines and ventilation and PPE recommendations outlined in the SDS for propane and this risk screen. 

7. FLAMMABILITY ASSESSMENT 

ASHRAE Standard 34 classifies propane as a Class A3 refrigerant. Propane is flammable when its 

concentration in air is in the range of 2.1 percent to 9.5 percent by volume (21,000 ppm to 95,000 ppm). 

In the presence of an ignition source (e.g., static electricity or a cigarette), an explosion or a fire could 

occur if the concentration of propane were to exceed the LFL of 21,000 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, servicing, and end-use. 

7.1 Flammability Risks at Equipment Manufacture 

Release of or exposure to propane may be possible at the charging and sealing steps on the production line 

at the manufacturing site. It is therefore important that all relevant standards be followed during the 

manufacture of ice machine refrigeration units. If the manufacture of commercial ice machines charged 

with propane occurs in the United States, EPA recommends that engineering controls should include 

normal and local ventilation (e.g., chemical hoods) for standard manufacturing procedures so workers can 

avoid physical contact with the refrigerant and to limit emissions. In general, use of appropriate PPE

consistent with OSHA guidelines is recommended, such as splash goggles, mechanically-resistant gloves 

when handling cylinders, chemically-resistant gloves (e.g., butyl rubber, chlorinated polyethylene, or

neoprene) when handling the gas mixture, and protective clothing. 

All propane storage and transport equipment should be installed with safety devices that minimize the 

likelihood of catastrophic releases. For example, the National Fire Protection Association (NFPA) 58 

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

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

storage and transportation requirements/guidelines. It is expected that refrigerants be properly stored and 

caution used within manufacturing facilities to minimize explosion risk and that workers adhere to the

requirements set by OSHA under 29 CFR 1910. OSHA requirements include proper ventilation and 

storage practices within manufacturing facilities to prevent fire and explosion. Good manufacturing 

practices should be adhered to during the manufacture of equipment containing propane, e.g., using proper 

ventilation. 

7.2 Flammability Risk at Servicing and End-Use 

The risk of flammability during servicing and end-use for the reasonable worst-case scenario (see Section 

5) was investigated for propane. Both servicing and end-use of propane ice machines are expected to take 

place in the same space (i.e., the installation and use location). In order to determine the potential
March 29, 2016 – Final 

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flammability risks during servicing or end-use in case of a catastrophic release of refrigerant, modeled 

concentrations of propane immediately following the release of refrigerant were compared with the LFL 

for propane. The results of the flammability assessment are presented in Table 6. 

Table 6. Flammability Assessmenta

Scenario Charge Size (g) Effective Room 

Size (m3) 

Vertical 

Concentration 

Gradient 

Maximum 

Instantaneous 

Concentration 

 (ppm) b,c

Reasonable Worst-Case Scenario 1 

150 22 (780 ft3)

d

Yes 21,430 

Reasonable Worst-Case Scenario 2 No 3,570 

Reasonable Worst-Case Scenario 3 150 120 (4,240 ft3) Yes 3,860 

Threshold Analysis 1: Charge Size 147 22 (780 ft3)

d

 Yes 21,000 

Threshold Analysis 2: Charge Size 820 120 (4,240 ft3) Yes 21,000 

Threshold Analysis 3: Room Size 150 ~22 (780 ft3)

d

 Yes 21,000 

Bold font indicates modeling results. 

a Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options.

b

 LFL of propane is 21,000 ppm. 

c Values provided in this column refer to the concentration in the lower 0.4 meters of the room, which presents the most conservative 

risk as 95 percent of the leaked refrigerant is present in this space. 

d Room sizes for Reasonable Worst-Case Scenarios 1, 2 and Threshold Analyses 1, 3 differ by less than 1 m3

 but appear to be equal 

due to independent rounding. 

As presented in Table 6, the maximum instantaneous concentration in the lower 0.4 meters of the room 

does not exceed the LFL for propane (i.e., 21,000 ppm) in all reasonable worst-case scenarios, excluding 

Reasonable Worst-Case Scenario 1. Although Reasonable Worst-Case Scenario 1 exceeds the LFL for 

propane, this exceedance is by approximately 2 percent, which is a small enough margin to reconsider the 

conservativeness of the assumptions used in the analysis. [ ]. Furthermore, commercial kitchen spaces are 

often connected to other rooms (e.g., an eat-in space, hallway) through open pathways or swinging doors, 

which would also increase the effective volume of the space into which a refrigerant would be released, 

thereby reducing the likelihood that the instantaneous concentration of propane would exceed the LFL. As 

a result, release of a 150-gram unit does not present a significant flammability risk in the reasonable worstcase scenario for propane in commercial ice machines. 

The conditions at which a flammability concern would exist (i.e., when the maximum instantaneous 

concentration in the lower 0.4 meters of the room equals the LFL for propane) were also determined. 

• As shown under Threshold Analysis 1, a flammability concern could occur if the charge size of the 

commercial propane ice machine unit in a 22 m3

 (780 ft3) room is 147 grams or more, which is 

slightly smaller than the maximum charge size allowed by UL 563 (i.e., 150 grams). 

• As shown under Threshold Analysis 2, a flammability concern could occur if the charge size of the 

commercial propane ice machine unit in a 120 m3 (4,240 ft3

) room is 820 grams or more, which is 

approximately five times the maximum charge size allowed by UL 563 (i.e., 150 grams). 

• Using the charge size of 150 grams for commercial ice machines, as shown under Threshold 

Analysis 3, the volume of the room would have to be approximately ~22 m3 (780 ft3), or slightly 

larger than the minimum modeled room size provided by the submitter for flammability to be of 

concern. 

According to the results of this flammability analysis, the risk of fire is minimal if a commercial ice 

machine is installed in a room with volumes in accordance with standards and regulations and if it meets 

the requirements of UL 563, including a charge size of 150 grams. As restaurant kitchens can be smaller 
March 29, 2016 – Final 

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than those modeled in this assessment and because persons or equipment in the room may reduce the 

effective volume of the space, refrigeration units containing propane should not be installed in enclosed 

areas with effective volumes less than indicated by relevant safety standards (e.g., ASHRAE 15, 34, and 

UL 563) unless additional steps are taken to protect against a flammability risk (e.g., higher ventilation 

rates). 

EPA recommends that warning labels are present on the equipment indicating that flammable refrigerants

in use as well as notifying the user to read the equipment use instructions that provide safety guidelines for 

handling propane. These guidelines should be followed to mitigate flammability risk. The installation of 

leak prevention devices would further protect against the very limited risk of explosion. During servicing 

operations, EPA recommends that the ventilation requirements outlined in the SDS for propane are 

followed through the use of fans or other mechanical ventilation devices and that portable refrigerant

detectors are used to alert technicians to the presence of flammable gases in order to mitigate the risk of 

fire or explosion during catastrophic leak. It is also important that only properly trained and certified 

technicians handle propane. As a further precaution, certification requirements and training programs for 

technicians that handle propane should be developed using these guidelines. 

8. ASPHYXIATION ASSESSMENT 

The risk of asphyxiation for the reasonable worst-case scenarios described in Section 5 were investigated 

for propane. In this section, risk of asphyxiation is assessed in three ways: 

1) Modeling the oxygen concentration under the charge size and room size specified in the worstcase scenario, 

2) Performing a threshold analysis of minimum charge 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 room size at which an asphyxiation risk could 

occur with the charge size specified in the worst-case scenario (i.e., room sizes smaller than this 

are expected to cause an asphyxiation risk). 

This analysis does not consider ventilation or conditions that are likely to occur that would increase

oxygen levels to which individuals would be exposed, such as open doors or windows, fans operating, 

conditioned airflow (either heated or cooled), or even openings at the bottom of doors that allow air to 

flow in and out. As specified in Section 5, the reasonable worst-case scenario assumes a vertical 

concentration gradient. If the proposed substitute passes the screening analysis with these restrictive 

assumptions in place, it can be reasonably assumed that no risks of asphyxiation will be present under realworld conditions. The results of the asphyxiation assessment are summarized in Table 7 below. 

Table 7. Asphyxiation Assessmenta,b 

Scenario Charge Size (g) Effective Room Size (m3) 

Percent Oxygen 

Concentration in 

Lower 0.4 Meters 

Reasonable Worst-Case Scenario 1 150 22 (780 ft3) 21% 

Reasonable Worst-Case Scenario 2 150 120 (4,240 ft3) 21% 

Threshold Analysis 1: Charge Size 2,730 22 (780 ft3) 12% 

Threshold Analysis 2: Room Size 150 1.2 (42 ft3) 12% 

Bold font indicates modeling results. 
March 29, 2016 – Final 

11 

a

 Cells highlighted in green are the scenarios in which the charge and room sizes evaluated in this risk screen are acceptable according to the 

threshold analysis or the scenarios with acceptable oxygen concentrations, given various modeling assumption options. 

b

 The typical concentration of oxygen in air is considered to be 21 percent (Mackenzie & Mackenzie 1995). 

In order for a risk of asphyxiation to occur, the normal concentration of oxygen in air (21 percent) must be 

reduced to 12 percent.11 Based on the reasonable worst-case scenario modeling, a release of propane from 

commercial ice machines has an insignificant impact on the concentration of oxygen in the air and 

therefore does not present a significant risk of asphyxiation. This modeling does not take into account any 

ventilation which is likely to occur, as mentioned above, so the actual asphyxiation risk to person(s) is 

likely to be even smaller than modeled. 

For the asphyxiation threshold analyses shown in Table 7, the conditions at which an asphyxiation concern 

would exist were determined. 

• As shown under Threshold Analysis 1, the charge size of the commercial ice machine in a 22 m3

(780 ft3) room would have to be at least 2,730 grams for asphyxiation to be a concern, which is 

approximately 18 times greater than the maximum charge size allowed by UL (i.e., 150 grams). 

• Using the charge size of 150 grams for commercial ice machines, as shown under Threshold 

Analysis 2, the volume of the room would have to be approximately 1.2 m3 (42 ft3

), or 

approximately 18 times smaller than the size of the minimum modeled restaurant kitchen for 

asphyxiation to be of concern. 

Based on the worst-case modeling results and threshold analysis, EPA does not believe that the use of 

propane in commercial ice machines poses a significant risk of asphyxiation or impaired coordination to 

personnel, provided systems are installed in appropriate spaces according to guidelines from the 

manufacturer and the SDS for propane. 

9. END-USE EXPOSURE ASSESSMENT 

This section presents estimates of potential end-user exposures to propane in the event of a catastrophic 

release from the proposed substitute’s use in commercial ice machines. An end-use exposure analysis was 

performed to examine potential catastrophic releases of propane under the reasonable worst-case scenario 

outlined in Section 5. 

For the end-use exposure assessment scenario, 30-minute TWA exposures for the proposed substitute were

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

concentrations on a minute-by-minute basis. Estimates for acute/short-term end-use exposures resulting

from catastrophic leakage of refrigerant from a commercial ice machine were examined. As discussed in 

Section 5, the full charge of the unit is assumed to be emitted over the course of 1 minute. The analysis 

was undertaken to determine the 30-minute TWA exposures of propane, which were then compared to the 

standard toxicity limits presented in Table 4 to assess the risk to end-users. The estimated TWA values are 

fairly conservative as the analysis reflects minimal airflow (i.e., natural ventilation), but does not consider 

mechanical ventilation such as fans, conditioned airflow (either heated or cooled) and other variables that 

would reduce the levels to which individuals would be exposed. Table 8 displays the estimated exposures 

to propane at end-use. 

 

11 Twelve percent oxygen in air is the NOAEL for hypoxia (ICF 1997). 
March 29, 2016 – Final 

12 

Table 8. End-Use Exposure Assessment for Propanea

Scenario Charge Size 

(g) 

Room Size 

(m3) 

Vertical 

Concentration 

Gradient 

30-min TWA EndUse Exposure 

(ppm)b

Reasonable Worst-Case Scenario 1 150 22 (780 ft3

) Yes 2,150 

Reasonable Worst-Case Scenario 2 No 360 

Reasonable Worst-Case Scenario 3 150 120 (4,240 ft3) Yes 390 

Threshold Analysis 1: Charge Size 480 22 (780 ft3)

Yes 6,900 Threshold Analysis 2: Room Size 150 7 (250 ft3

)

Bold font indicates modeling results. 

a

 Cells highlighted in green are the scenarios with acceptable exposure levels given various modeling assumption options. 

b 30-minute AEGL-1; see Table 4 for more information.

Under the reasonable worst-case scenario described in Section 5 for commercial ice machines, the 

anticipated 30-minute TWA exposures of propane following a catastrophic release of a 150-gram unit do 

not exceed its 30-minute AEGL (i.e., 6,900 ppm). In addition, these exposure estimates were derived using 

conservative assumptions (e.g., minimum room volume, low ventilation rate) that do not necessarily reflect 

the actual room attributes where propane ice machines will be installed. Specifically, the estimated 

exposure represents concentrations of leaked refrigerant in the bottom 0.4 meter (1.3 feet) of the room, 

accounting for 95 percent of the refrigerant charge in this lower portion of the room. The probability that 

an individual would be present in this lower portion (e.g., prone or supine on the floor or a crawling infant) 

in the event of the catastrophic release of refrigerant is low. Furthermore, commercial kitchen spaces are 

often connected to other rooms (e.g., an eat-in space, hallway) through open pathways or swinging doors, 

which would increase the effective volume of the space into which a refrigerant would be released, thereby 

reducing the likelihood that end-users would be exposed to modeled concentrations. 

To further analyze potential risks of exposure during end-use, threshold analyses were conducted to 

determine the room size and charge size requirements that ensure that the use of propane in this end-use 

does not present risk to end-users or servicing technicians. Based on these results, EPA recommends that 

for a room volume of 22 m3 (780 ft3

), the charge size is consistent with the proposed limit in UL 563 and 

does not exceed 150 grams. The analysis also indicates a 150-gram refrigeration unit should not be 

installed in a room of effective volume less than 7 m3 (250 ft3

) (see Threshold Analysis 2 in Table 8). 

To prevent exposure and potential serious side effects during larger releases, EPA recommends that the

RCL for propane (i.e., 5,300 ppm or 9.5 g/m3) is not exceeded in any location where a propane system is 

installed, unless proper leak protection devices are in place in order to prevent exposures of propane

beyond the recommended limits. Proper leak protection devices, engineering control requirements, and 

adherence to the SDS will further ensure that exposure limits are maintained below those described in 

Table 8. 

10. OCCUPATIONAL EXPOSURE ASSESSMENT 

This section assesses potential exposures to workers during manufacture of propane, and installation, 

servicing, and disposal of propane ice machines. To ensure that use of the proposed substitute in 

commercial ice machines does not pose an unacceptable toxicity risk to workers during servicing and 

disposal, occupational exposure modeling was performed using a box-model approach. For a detailed 

description of the methodology used for this screening assessment, the reader is referred to the 

occupational exposure and hazard analysis described in Chapter 5 of the Background Document. 
March 29, 2016 – Final 

13 

For charging, servicing, and disposal activities, the release rate per event was multiplied by the number of 

events estimated to occur over a workday. During charging and servicing, the release per event was 

conservatively assumed be 0.4 percent of the equipment charge. For equipment charging and servicing, the 

number of events per workday was conservatively assumed that eight events of servicing a unit by one 

servicing technician occur in an 8-hour work day (see Section 10.2). 

For disposal, the release per event was conservatively assumed to be 100 percent of the equipment charge 

(representing a catastrophic release). It was 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 the

catastrophic release (i.e., 100 percent). The remaining 9 units were assumed to release an incidental 

amount of refrigerant (i.e., 1 percent per unit) from the connecting and disconnecting of lines, as it is likely 

that if a worker was exposed to the entire charge of a system during disposal activities, they would 

immediately stop working, clear the area until all refrigerant has been removed from the space (e.g., 

through ventilation), and adhere to the exposure procedures recommended in the SDS for the proposed 

substitute (see Section 10.3). 

The modeled exposure concentrations were compared to short-term occupational exposure limits at 

charging and servicing and long-term exposure limits at disposal. 

10.1 Occupational Exposure at Manufacture of Substitute 

Propane is produced around the world, including in the United States, and is used for a wide variety of 

refrigerant and non-refrigerant uses. During manufacture of propane, the SDS should be referenced and 

proper engineering controls and PPE used. 

Propane is not expected to pose a risk to workers during manufacture or blending when the engineering 

controls and PPE recommendations referenced in the SDS propane are followed. Release points/exposure 

in chemical manufacturing would typically be where temporary lines are connected or disconnected (i.e., 

filling of portable cylinders and portable bulk containers). Refrigerant quality control testing may result in 

release of de minimus quantities of refrigerant, which would typically be to exhaust ducts or fume hoods. 

Engineering controls should include normal and local ventilation (e.g., chemical hoods) and vapor-in-air 

detection systems for standard manufacturing procedures so workers can avoid physical contact with the

refrigerant and to achieve emission control. In general, use of PPE consistent with OSHA guidelines is

recommended, such as respiratory protection (including a self-contained breathing apparatus [SCBA] in 

case of insufficient ventilation), tightly sealed goggles, and protective gloves (OSHA 1994). EPA believes 

that when proper handling and disposal guidelines are followed in accordance with both good industrial

hygiene and manufacturing practices and the SDS for propane, there is no significant risk to workers 

during the manufacture of propane. 

10.2 Occupational Exposure at Charging and Servicing 

Commercial ice machines would typically be charged by the Original Equipment Manufacturer (OEM). 

During OEM system manufacture (i.e., charging at OEM location), points of release for charging and 

servicing these leak-tight systems would be from connection/disconnection of temporary lines for charging 

and recovery equipment. 

Charging occurs within an enclosed area equipped with automatic ventilation, refrigerant detectors, and 

alarm systems. [ ]. 

During servicing, used refrigerant from propane ice machines is pumped into a canister, where it is stored 

until it is recycled (i.e., filtered and reused). Isolation and evacuation of lines or equipment prior to 

servicing or repair and the use of compatible seals, gaskets, O-rings, thread sealants, and minimization of 
March 29, 2016 – Final 

14 

threaded joints all contribute to limiting releases. Room ventilation, leak monitors, and alarms also 

minimize exposure. 

Installation and servicing activities for commercial ice machines are not expected to result in significant 

worker exposure when certified technicians follow the procedures outlined in the propane SDS and 

maintenance manual, undergo proper training, and wear appropriate PPE (e.g., gloves and safety glasses). 

Nevertheless, the potential occupational exposure during servicing was analyzed. The maximum 30-

minute TWA exposures for propane were estimated and compared to the STEL (see Table 9). The 

modeling results indicate that the maximum anticipated occupational exposure concentrations at no point 

exceed the STEL for propane. 

Table 9. Occupational Risk Assessment at Servicinga 

Component 

30-minute TWA Occupational 

Exposure (ppm) Short Term Exposure 

Limit (ppm) Charge Size: 150 grams

Propane 1.2 6,900b

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 30-minute AEGL-1; see Table 4 for more information.

The estimated exposures were derived using conservative assumptions, and represent a worst-case scenario 

with a low probability of occurrence. These types of systems are typically serviced by trained personnel 

using proper industrial hygiene techniques and using proper engineering controls (e.g., local ventilation, 

refrigerant detectors, and alarm systems). Thus, EPA does not believe that installation or servicing of 

commercial ice machines containing propane presents a significant concern to workers. 

10.3 Occupational Exposure at Disposal 

Disposal of propane ice machines is expected to occur with limited frequency (up to approximately ten 

disposal events per day) at disposal facilities and with limited duration of exposure to the installed

refrigerant. Typically, potential exposures to the refrigerant during recovery and disposal are expected to 

occur during activities related to decommissioning refrigeration systems (e.g., attaching of hoses 

associated with draining or otherwise discharging of refrigerant from the refrigeration units into cylinders) 

and would be similar to those during servicing, because similar refrigerant charging and/or recovery 

equipment would be used (see Section 10.2 and Table 9 for information and modeling results related to 

exposure during servicing activities). Such activities and related exposure is anticipated to occur within 15-

30 minutes (per event/day). 

Table 10 displays the maximum estimated 8-hour TWA occupational exposure levels for propane and each 

of its potential impurities during disposal. To model a worst-case scenario, it was assumed that of the 10 

disposal events, 9 units are properly disposed of with only incidental releases of refrigerant (i.e., 1 percent 

per unit) followed by the disposal of one unit that results in a catastrophic release of refrigerant (i.e., 100 

percent of the equipment charge). Because modeled exposure levels are significantly lower than the 8-hour 

exposure limits for propane and each of its potential impurities, occupational exposure to the proposed 

substitute during disposal is not considered a toxicity risk. Further, estimated exposures were derived using 

conservative assumptions (e.g., no ventilation) and represent a worst-case scenario with a low probability 

of occurrence. These types of systems are typically disposed of by trained personnel using proper 

industrial hygiene techniques while wearing PPE. 
March 29, 2016 – Final 

15 

Table 10. Occupational Risk Assessment at Disposala

Component 

8-hour TWA Occupational 

Exposure (ppm) 8-Hour Long Term 

Exposure Limits (ppm) Charge Size: 150 grams

Propane 58 1,000b

Bold font indicates modeling results. 

a Cells highlighted in green are the scenarios with exposure levels deemed to be acceptable given 

various modeling assumption options. 

b

 OSHA PEL and NIOSH REL 

Although anticipated occupational exposures are well below the exposure limit for propane for units with a 

charge of 150 gram, the recommendations for proper engineering controls and PPE in the SDS for propane

should be followed. Adequate ventilation should always be established during any use, handling, or 

storage of propane. Engineering controls should include vapor-in air detection systems and local exhaust 

ventilation during use of propane to prevent dispersion throughout the workplace. In addition, an eye wash 

and safety shower should be near locations where propane is stored and ready for use. In general, use of 

PPE is recommended, such as splash goggles, mechanically-resistance gloves when handling cylinders, 

and chemically-resistant gloves when handling the gas mixture (e.g., butyl rubber, chlorinated 

polyethylene, or neoprene). EPA believes that if proper handling and disposal guidelines are followed in 

accordance with good industrial hygiene and manufacturing practices and the SDS for propane, there is no 

significant risk to workers during the disposal of propane in commercial ice machines. 

11. GENERAL POPULATION EXPOSURE ASSESSMENT 

This section presents an assessment of potential risks to the general population posed by the use of propane 

in ice machines. The general population is defined in this risk screen as non-personnel who 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 activities only), or 

recycling centers, rather than consumers at end-use. 

Propane is not expected to cause a significant risk to human health in the general population when 

manufactured for use and used as a refrigerant in commercial ice machines. 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 temperature, propane is a gas; therefore, releases to ground or surface water 

are not anticipated, as propane is anticipated to dissipate into the atmosphere upon release to outside air 

(i.e., because natural ventilation rates would be higher and there is no enclosed space to maintain a high 

concentration of propane). Should air releases during manufacturing operations occur, engineering controls 

should be used (e.g., carbon absorption scrubbers) to collect propane and prevent the release of the 

chemical to the atmosphere. 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 propane is not expected to pose a significant toxicity risk to the general population. 
March 29, 2016 – Final 

16 

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