May 30, 2014 -- Final

1

Significant New Alternatives Policy Program 

Refrigeration and Air Conditioning Sector

Risk Screen on Substitutes for CFC-12, HCFC-22, and R-502 in Retail Food

Refrigeration

Substitute: R-441A

This risk screen is restricted to retail food refrigeration applications covered under UL 471: 

Commercial Refrigerators and Freezers.

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

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

1. INTRODUCTION

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

diplomatic and legislative efforts that have taken 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-use applications within all of the major ODSusing 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 R-441A as a substitute for CFC-12, HCFC-22, and R-502 in the retail 

refrigeration end-use, specifically for stand-alone commercial refrigerators, freezers, and refrigerated

display cases. Table 1 presents the composition of the proposed substitute.

Table 1. Composition of R-441A

Constituent Chemical Formula CAS Number Concentration

(Weight Percent)a

Propane C3H8 74-98-6 55%

n-Butane C4H10 106-97-8 36%

Isobutane C4H10 75-28-5 6%

Ethane C6H14 74-84-0 3%

a There are no impurities of toxicological or ecological significance anticipated for this formulation. Isomers of hydrocarbons present in 

formulation mixture will exist, but are not considered to be an impurity, contaminant or byproduct.

Section 2 summarizes the results of the risk screen for the proposed substitute blend listed in Table 1. 

The remainder of the risk screen is organized into the following sections:

 Section 3: Atmospheric Assessment

 Section 4: Volatile Organic Compound Assessment 

 Section 5: Discussion of End-Use Scenario Modeled 
May 30, 2014 -- Final

2

 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

R-441A is recommended for SNAP approval for the retail food refrigeration end-use for stand-alone 

refrigeration equipment that comply with Underwriters Laboratory (UL) Standard 471: Commercial 

Refrigerators and Freezers. EPA's risk screen indicates that the use of the proposed substitute will be less 

harmful to the atmosphere than the continued use of CFC-12, R-502, and HCFC-22 as it is less harmful to 

the ozone layer, has lower climate impact, and a shorter atmospheric lifetime. Three of the four 

components of R-441A—propane, n-butane, and isobutane—are subject to volatile organic compound 

(VOC) regulations under the CAA (40 CFR 51.100(s)). Based on analysis of potential impacts of 

hydrocarbon refrigerant emissions on ground-level ozone concentrations, VOC emissions from the use of 

R-441A in retail food refrigeration end-use for stand-alone refrigeration equipment are not anticipated to 

contribute significantly to ground level ozone concentrations in the United States. It is expected that the 

material safety data sheet (MSDS) for R-441A and good manufacturing practices will be adhered to.

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

protective gloves, tightly sealed goggles, protective work clothing, and suitable respiratory protection in 

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

(OSHA) guidelines will be used during manufacture, installation and servicing, and disposal of retail food 

refrigeration systems using R-441A. Because retail food refrigeration systems are to be installed in 

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

equipment maintenance manual for R-441A, significant toxicity or flammability risk to consumers is also 

unlikely. Additional safeguards, including specified refrigerant concentration limits (RCL) of R-441A 

components, are also provided by adherence to industry standards including American Society of 

Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standards 15,134,2and 623and 

Underwriters Laboratory (UL) Standard 471.4

3. ATMOSPHERIC ASSESSMENT

This section presents an assessment of the potential risks to atmospheric integrity posed by the use of R441A in commercial refrigeration and freezers. The ozone depletion potential (ODP), global warming 

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

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

shorter atmospheric lifetime when compared to CFC-12, R-502, and HCFC-22. In addition, R-441A also 

has lower climate impact and a shorter atmospheric lifetime than those predicted for other substitutes 

examined in the Background Document as well as commonly utilized substitutes R-410A and R-404A. 

 

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 471: Commercial Refrigerators and Freezers establishes safety requirements for the construction, electrical system, 

electrical components, refrigeration system, and performance of commercial refrigerators and freezers. 
May 30, 2014 -- Final

3

Thus, EPA believes that the use of R-441A would result in substantially less harm to the climate and 

ozone layer than the continued use of ODS and commonly used ODS substitutes.

Table 2. Atmospheric Impacts of R-441A Components Compared to Other Retail Food 

Refrigerants

Refrigerant Ozone Depleting Potential

(ODP)

a

Global Warming Potential

(GWP)

b

Atmospheric Lifetime in 

Years (ALT)

Propane 0 3.3 0.03

a

n-Butane 0 4.0 0.018c

Isobutane 0 ~4 0.016

a

Ethane 0 5.5 0.21c

CFC-12 0.82 10,900 100b

R-502d 0.2 4,650 NAe

HCFC-22 0.13 1,810 12a

HFC-134a 0 1,430 14b

R-404Af 0 3,922 NAg

a WMO 2010 Scientific Assessment Report (2011)

b

IPCC 4th Assessment Report (Forster et al. 2007)

c

IPCC/TEAP (2005)

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

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

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

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

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

ALT for HFC-125 is 29 years, and the ALT for HFC-134a is 14 years.

4. VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS

Three of the four components of R-441A—propane, n-butane, and isobutane –- are regulated as VOCs 

under the CAA (40 CFR 51.000), and as such, emissions of R-441A should be controlled. A separate 

analysis was prepared by EPA (2014) to evaluate the potential impact of the use of hydrocarbon 

refrigerants on ground level ozone concentrations in the United States. The analysis estimated refrigerant 

emissions from refrigeration and air conditioning equipment, which were assumed to contain propylene, 

isobutane, and/or propane 4under different scenarios. Under the most conservative scenario it was 

assumed that propylene was used in all refrigeration and air conditioning equipment. In the most realistic 

scenario, all three hydrocarbons were assumed to be used in 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 included in the evaluation included selfcontained refrigeration 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 U.S. EPA’s Vintaging Model, and their potential contributions to ozone 

concentrations were assessed using U.S. EPA’s Community Multiscale Air Quality (CMAQ) model. 

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

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

formation. The ozone concentrations were estimated for the 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 realistic 

scenario, hydrocarbon refrigerants could potentially increase the maximum 8-hour average ground level 

ozone by lesson more than 0.15 ppb in Los Angeles, the city with the greatest ozone problem. This is 

roughly 0.2 percent of the current National Ambient Air Quality Standard (NAAQS) for ozone of 75 ppb.

 

4 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.
May 30, 2014 -- Final

4

In the most conservative case which assumed that the most reactive hydrocarbon, propylene, was used in 

all refrigeration and air conditioning equipment, there could be an incremental maximum increase of the 

8-hour average as high as 6.61 ppb ozone, or an increase of up to 9 percent of the NAAQS. However, this 

upper bound level of increase is not likely, as most ozone nonattainment areas are not VOC-limited (i.e., 

the formation of ozone in these areas are not by limited by VOC emissions, but by other compounds such 

as nitrogen oxides [NOx]). In addition, the analysis assumed no use of VOC-exempt refrigerants which 

may be used in the refrigeration and air conditioning end-uses. Based on the results of this analysis, VOC 

emissions from the use of R-441A in self-contained retail food refrigeration equipment are not anticipated

to contribute significantly to ground level ozone concentrations in the United States.

5. DISCUSSION OF END-USE SCENARIOS MODELED

R-441A has been proposed for the retail food refrigeration end-use, specifically for stand-alone 

commercial refrigerators, freezers, and refrigerated display cases. The submission states that R-441A

retail food refrigeration equipment will have a typical charge size of 103 grams for commercial 

refrigerators, 150 grams for commercial freezers, and 135 grams for refrigerated display cases; however,

UL Standard 471: Commercial Refrigerators and Freezers states that commercial refrigeration equipment 

containing a flammable refrigerant may have a charge size up to 150 grams of A3 refrigerant. 

To represent a reasonable worst-case scenario, it is assumed that a catastrophic leak of refrigerant occurs 

while a commercial freezer is installed at the end-use. To account for retail food refrigeration models

which could utilize the maximum amount of refrigerant allowed under UL 471, the reasonable worst-case 

scenario is modeled using a charge size of 150 grams. Because retail refrigeration equipment can be 

installed in a wide range of locations with varying room volumes, the analysis in this risk screen 

conservatively assumes that the commercial refrigeration unit is located in the kitchen of a small fast food 

restaurant with a volume of 50 m3that is connected to a customer area of 100 m3(A.S. Trust & Holdings, 

Inc. 2012).5 Under the reasonable worst-case scenario, the full charge of the unit is assumed to be emitted 

over the course of one minute, into the food preparation area (50 m3) with a conservative ventilation rate 

of 1.5 air changes per hour (A.S. Trust & Holdings, Inc. 2012 citing Turk, et. al. 1989). A vertical 

concentration gradient is also assumed since R-441A is denser than air (specific gravity of R-441A 

relative to air is 1.67 [air = 1]) and will settle in higher concentrations closer to the ground. In order to 

simulate the vertical concentration gradient, it is assumed that 95 percent of the leaked refrigerant mixes 

evenly into the bottom 0.4 meter of the room, and the rest of the refrigerant mixes evenly in the remaining 

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 Assumption

Refrigeration Unit Commercial Freezer

Room Food Preparation Area of Small Fast Food 

Restaurant

Charge Size (g) 150

Length of Release (minutes) 1

Room Size (volume - m3) 50

Room Ventilation (air changes per 

hour) 1.5

Vertical Concentration Gradient Yes

 

5 Additional use locations range from small fast food restaurants and convenience stores to large supermarkets and grocery stores. 

The smallest minimum convenience store found during a California survey has a volume of 244 m3(Armines 2009), and a 

relatively small fast food restaurant has a volume of 317 m3(Clarke et al, 1990). The small food preparation area (50m3) in a fast 

food restaurant (100 m3) is the most conservative space volume, and was therefore the volume used to represent a reasonable, 

worst-case scenario for this analysis. 
May 30, 2014 -- Final

5

To address the variability in installation locations and room volumes for retail food equipment, this risk 

screen incorporates threshold analyses in addition to the worst-case scenario modeling, in order to 

determine the room size and charge size requirements to ensure that use of R-441A in retail food 

refrigeration does not present risk to consumers or servicing technicians.

6. POTENTIAL HEALTH EFFECTS

To assess potential health risks from exposure to the proposed substitute in retail food refrigeration, EPA 

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

different scenarios. To protect consumers from the potential dangers of a catastrophic leak from the 

refrigeration unit, ASHRAE Standard 34 determined refrigerant concentration limits (RCLs) for the 

components of R-441A which are intended to reduce the risks of acute toxicity, asphyxiation, and 

flammability hazards in normally occupied, enclosed spaces during refrigerant use (ASHRAE 2010b). 

ASHRAE Standard 15 implements the aforementioned standard, requiring that “the concentration of 

refrigerant in an enclosed space following a complete discharge of a high-probability system shall not 

exceed the RCL” (ASHRAE 2010a). As such, this risk screen references the RCL of the R-441A 

components in addition to the lower flammability limit, hypoxia NOAEL, and exposure limits, as an 

additional, conservative 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 to available occupational exposure limits. Potential 

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

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

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

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

short-term, end-use exposures were compared to an excursion limit, which was calculated according to 

the methodology described in ACGIH (2004).6 Table 4 lists the relevant toxicity limits of each 

component of R-441A, and is followed by Table 5, which provides an explanation of each toxicity limit. 

EPA’s approach for identifying or developing these values is discussed in Chapter 3 of the Background 

Document. 

 

6

It should be noted that this risk screen evaluates both short-term occupational and end-use (i.e., non-occupational) exposure to 

ethane by comparison to the excursion limit, which is typically used to evaluate short-term occupational exposure. EPA believes, 

however, that in the absence of an AEGL, STEL, or ERPG, the excursion limit provides a reasonable proxy. Notably, the ACGIH 

methodology (i.e., a calculation of three times the TLV-TWA) has also been used by DOE (2008) to develop temporary 

emergency exposure limits (TEEL) for ethane (3,500 mg/m

3

or 2,900 ppm 15-min TWA), which apply to the general population.
May 30, 2014 -- Final

6

Table 4. Exposure Limits of R-441A Components

R-441A 

Component

8-hr WGL (Long-term 

Exposure)

ppm

EGL (Short-term Exposure)

ppm

Refrigerant Concentration 

Limit (RCL)

ppm

Propane 1,000a

(OSHA PEL)

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

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

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

Isobutane 1,000b (ACGIH TLV) 6,900f 4,000g

Ethane 1,000b (ACGIH TLV)

3,000h(30 min ACGIH Excursion 

Limit) 

2,900i(15-min TEEL-1)

7,000g

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

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

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

(ACGIH 1991; Braker 1980), a value much greater than 10,000 ppm would have been appropriate. However, the revised IDLH for propane is 2,100 

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

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

d AEGL-1 available at: http://www.epa.gov/opptintr/aegl/pubs/tsd96.pdf

e AEGL-1 available at: http://www.epa.gov/opptintr/aegl/pubs/tsd102.pdf

f Because n-Butane and isobutane have the same molecular formula, EGL for isobutane is conservatively assumed to be that for n-Butane. 

However, OSHA (2004) notes the following regarding isobutane: “OSHA does not have a PEL for isobutane, which is affirmed as "generally 

recognized as safe" as a direct human food ingredient (21 CFR 184.1165). No toxic effects reported below 18,000 ppm.”

g ASHRAE (2010b)

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

iDOE (2008)

Table 3. 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

Exposure Limit Definition Explanation

Short-Term Exposure

RCL Refrigerant Concentration 

Limit

The RCL for a refrigerant is intended to reduce the risks of acute toxicity, 

asphyxiation, and flammability hazards in normally occupied, enclosed 

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

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

Concentration Limit (FCL). Determination assumes full vaporization with 

no removal by ventilation, dissolution, reaction, or decomposition and 

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

STEL Short-Term Exposure Limit A 15-minute time-weighted average (TWA) exposure that should not be 

exceeded at any time during a workday, even if the 8-hour TWA is within 

the TLV–TWA, set by ACGIH. 

AEGLb,c

Acute Exposure Guideline 

Level 1

AEGL-1 is the airborne concentration of a substance above which it is 

predicted that the general population, including susceptible individuals, 

could experience notable discomfort, irritation, or certain asymptomatic 

nonsensory effects. 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 AEGL-3 is the airborne concentration (expressed as ppm or mg/m3) of a 
May 30, 2014 -- Final

7

Level 3 substance above which it is predicted that the general population, 

including susceptible individuals, could experience life-threatening health 

effects or death.

ERPG Emergency Response 

Planning Guideline 1 

The maximum airborne concentration below which it is believed that 

nearly all individuals could be exposed for up to 1 hour without 

experiencing other than mild transient health effects or perceiving a 

clearly defined, objectionable odor according to AIHA. 

Emergency Response 

Planning Guideline 2 

The maximum airborne concentration below which it is believed that 

nearly all individuals could be exposed for up to 1 hour without 

experiencing or developing irreversible or other serious health effects or 

symptoms which could impair an individual's ability to take protective 

action according to AIHA.

Emergency Response 

Planning Guideline 3 

The maximum airborne concentration below which it is believed nearly 

all individuals could be exposed for up to 1 hour without experiencing or 

developing life-threatening health effects according to AIHA.

Excursion Limit d Excursion Limit Because methane (and other short-chain alkane gases through butane) 

does not have a TLV-short-term exposure limit, an excursion limit may 

be applied. Excursions in worker exposure levels may exceed 3 times 

the TLV-TWA for no more than a total of 30 minutes during a workday, 

and under no circumstances should they exceed 5 times the TLV-TWA, 

provided that the TLV-TWA is not exceeded according to ACGIH. 

IDLH Immediately Dangerous to 

Life and Health

If exposed to this concentration, room occupants are expected to be able 

to escape the room within 30 minutes without experiencing escapeimpairing or irreversible health effects.

Long-Term Exposure

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

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

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

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

effect according to ACGIH. 

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

b EPA (2012)

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

d ACGIH (2004)

According to the MSDS, exposure to R-441A may be hazardous if inhalation, skin contact, or eye contact 

with R-441A occurs. The most likely pathway of exposure is through inhalation. R-441A can cause 

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

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

nausea, vomiting, depression of all senses, and also unconsciousness. Under some circumstances of overexposure (i.e., oxygen levels fall below 6 percent by volume), death may occur. In addition, at high 

concentrations, propane, a major component of the R-441A blend, can act as a narcotic and cause central 

nervous system depression, including dizziness, drowsiness, and headaches. 

If R-441A is inhaled, person(s) should be immediately removed and exposed to fresh air. In accordance 

with the MSDS, EPA further recommends that if breathing is difficult, person(s) be given oxygen, 

provided a qualified operator is present, and medical attention be sought. Rescuers should not attempt to 

retrieve victims of exposure to R-441A without adequate PPE. At a minimum, a self-contained breathing 

apparatus (SCBA) should be worn. Exposures of R-441A to the skin may cause frostbite. In the case of 

dermal exposure, the MSDS for R-441A recommends that person(s) immediately 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. 

Alternatively, if the fingers or hands are frostbitten, warm the affected area by placing it in the armpit; 

gently exercise the affected part while being warmed, and seek medical attention immediately. Exposures 
May 30, 2014 -- Final

8

of R-441A to the eyes could cause eye irritation. In case of ocular exposure, the MSDS for R-441A 

recommends that person(s) immediately flush the eyes, including under the eyelids, with copious amounts 

of water for 15 minutes. 

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

for this decision. The potential health effects of R-441A can be minimized by following the exposure 

guidelines and ventilation and PPE recommendations outlined in the MSDS for R-441A and this risk 

screen.

7. FLAMMABILITY ASSESSMENT

ASHRAE Standard 34 classifies R-441A as a Class A3 refrigerant. R-441A is flammable when its 

concentration in air is in the range of 2.05 percent and 9.25 percent by volume (20,500 ppm to 92,500 

ppm). In the presence of an ignition source (e.g., static electricity, a spark resulting from a switch 

malfunction, or a cigarette), an explosion or a fire could occur if the concentration of R-441A were to 

exceed the lower flammability limit (LFL) of 20,500 ppm. As such, R-441A may pose a significant 

safety concern for workers and consumers if it is not handled carefully. The remainder of this section 

assesses flammability risks and summarizes the recommended measures to ensure safe handling and use 

of the refrigerant during manufacture, servicing, and end-use. 

7.1 Flammability Risks at Manufacture

As indicated by the submitter, the manufacture of R-441A refrigerant (i.e., formulation mixing) and the 

charging of R-441A retail food refrigeration equipment (receiving, blending. and filling operations) 

occurs in a closed system; all units are completely sealed before delivery and installation. As a result, 

releases of R-441A during these manufacturing and installation operations in the presence of an ignition 

source are not anticipated. 

All R-441A storage and transport equipment should be installed with safety devices that minimize the 

likelihood of catastrophic releases. For example, NFPA 58 Liquefied Petroleum Gas Code (NFPA 2014) 

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. Similar equipment safety and procedural requirements should be developed for 

R-441A and other flammable refrigerants. EPA believes that because workers follow relevant safety 

standards in manufacturing facilities, the MSDS for isobutane, and OSHA requirements under 29 CFR 

1910 (e.g., proper ventilation and storage practices within manufacturing facilities to prevent fire and 

explosion), flammability during manufacture is not expected to be of concern.

7.2 Flammability Risk at Servicing and End-Use

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

scenario (see Section 5) was investigated for R-441A. Both servicing and end-use of R-441A retail food 

refrigeration equipment are expected to take place in the same space (i.e., the place of installation and 

use). In order to determine the potential flammability risks during servicing or end-use in case of a 

catastrophic release of refrigerant in a food preparation area (see Section 5), concentrations of R-441A 

immediately following the release of refrigerant were compared to the LFL for R-441A. The maximum 

instantaneous concentration of R-441A in the lower 0.4 meters of the room at a charge size of 150 grams 

would be approximately 8,490 ppm, which is 41 percent of the proposed substitute’s LFL (see Table 6). 

The maximum instantaneous concentration in the upper portion of the room for both modeled charge 

sizes is much lower, as only 5 percent of the leaked refrigerant is present in this area, which also has a 

greater volume than the lower 0.4 meters of the room. Table 6 presents the results of the analysis.
May 30, 2014 -- Final

9

Table 6. Flammability Assessmenta

Scenario Charge Size (g) Effective Room 

Size (m3)

Maximum Instantaneous 

Concentration

(ppm) b,c

Reasonable Worst-Case 150 50.0 (1,770 ft3

) 8,490

Threshold Analysis 1: Charge Size 354 50.0 (1,770 ft3

) 20,050

Threshold Analysis 2: Room Size 150 21.2 (749 ft3

) 20,050

Bold font indicates modeling results.

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

b Lower Flammability Limit of R-441A is equal to 20,500 ppm

c Values provided in these columns refer to the concentration in the lower 0.4 meters of the room

The results of the threshold analysis indicate that the charge size would have to be significantly larger, or 

the room size smaller, than what is assumed in the worst-case scenario (see Section 5) for a flammability 

risk to occur. As shown in Threshold Analysis 1, for flammability to be of concern within a room size of 

50 m3(1,770 ft3) (see Table 6), the charge size released would have to be at least 354 grams. As shown in 

Threshold Analysis 2, for flammability to be of concern for commercial freezers with a charge size of 150 

grams, the volume of the room would have to be 21.2 m

3 (749 ft3

) (see Table 6). 

It is unlikely that a store or restaurant as small as that determined in the flammability threshold analysis 

would exist and it is further unlikely that the entire refrigerant charge would accidentally release into the 

convenience store. In addition, R-441A is likely to be dispersed into the air evenly and almost 

instantaneously upon accidental release; the retail food refrigeration unit compressor is pressurized 

between 135 and 160 psi, which will cause R-441 to be released into the room (assumed to be at 

atmospheric pressure of approximately 14.7 psi) under high pressure, resulting in the refrigerant’s quick 

and turbulent release, and subsequent mixing into the air (A.S. Trust & Holdings, Inc. 2011). EPA 

recommends that the ventilation requirements outlined in the MSDS for R-441A are followed to mitigate 

the risk of fire or explosion during catastrophic leak during end-use or when servicing equipment using R441A. In addition, EPA recommends that retail food refrigeration equipment with charge sizes of 150 

grams are not installed in enclosed areas with volumes smaller than 21.2 m

3 (749 ft3

) in order to mitigate 

flammability risk. 

Catastrophic releases of large quantities of refrigerant, especially in areas where refrigerant is stored, 

could result in an explosion in the presence of an ignition source. For this reason, it is important that only 

properly trained and certified technicians handle R-441A. The submitter has provided safety guidelines 

for handling R-441A, which should be followed. As a further precaution, certification requirements and 

training programs for technicians that handle R-441A should be developed using these guidelines. 

During servicing operations, technicians should ensure that proper ventilation is in place through the use 

of fans (or other mechanical ventilation devices) and portable refrigerant detectors should be used to alert 

technicians to the presence of flammable gases in the area. Furthermore, EPA recommends that 

consumers should not be present during servicing activities.

It is recommended that retail food refrigeration equipment not be installed in small, poorly ventilated 

spaces such as very small enclosed areas or storage closets (especially as other equipment or appliances in 

the space would reduce the effective volume of the room). For retail food refrigeration equipment

installed in larger areas, the risk of fire and explosion is minimal. Retail food refrigeration equipment 

installed with R-441A should be clearly labeled as containing a flammable refrigerant and designed to 

prevent catastrophic leaks. The installation of leak prevention devices would further protect against the 

very limited risk of explosion. Because relevant safety standards and the MSDS for isobutane are 

followed by service technicians and because isobutane refrigeration units will be installed in areas with 

adequate space and ventilation, EPA believes that flammability during servicing and end-use is not 

expected to be of concern. 
May 30, 2014 -- Final

10

8. ASPHYXIATION ASSESSMENT

The risk of asphyxiation for the reasonable worst-case scenario was investigated for R-441A. In this 

section, risk of asphyxiation is assessed in three ways: 1) modeling the oxygen concentration under the 

charge size and room size specified in the worst-case scenario, 2) performing a threshold analysis of 

minimum charge size needed to cause an asphyxiation risk in the room size specified in the worst-case 

scenario 3) performing a threshold analysis of the maximum room size needed to cause an asphyxiation 

risk with the charge size specified in the worst-case scenario. This analysis does not consider ventilation 

or conditions that are likely to occur that would increase oxygen levels to which individuals would be 

exposed, such as open doors or windows, fans operating, conditioned airflow (either heated or cooled), or 

even openings at the bottom of doors that allow 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 real-world conditions. The results of the asphyxiation 

assessment are summarized in Table 7 below. 

Table 7. Asphyxiation Assessmenta

Scenario Charge Size (g)a

Effective Room Size 

(m3)

Percent Oxygen 

Concentration in

Lower 0.4 Meters

Reasonable Worst-Case 150 50.0 (1770 ft3) 21

Threshold Analysis 1: Charge Size 7,242 50.0 (1770 ft3) 12

Threshold Analysis 2: Room Size 150 1.0 (36.6 ft3) 12

 Bold font indicates modeling results.

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

b The typical 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) in the 

lower 0.4 meters of the room must be reduced to 12 percent.7 Based on the worst-case scenario modeling 

assumptions, R-441A in retail food refrigeration equipment does not present a significant risk of 

asphyxiation. As shown in Threshold Analysis 1, the minimum charge of R-441A necessary to reduce the 

oxygen levels to 12 percent in air in the lower 0.4 meters of a room of volume 50 m3(1,770 ft3) was 

calculated to be 7,242 grams assuming that 1) nitrogen and oxygen retain the same relative volumes in the 

rooms with the balance composed entirely of R-441A, and 2) the pressure of the room does not increase 

significantly with the addition of the refrigerant. This amount represents nearly 50 times the intended 

charge of approximately 150 grams for a single R-441A retail food refrigeration unit. Because this 

threshold modeling does not take into account any ventilation which is likely to occur, such as 

conditioned airflow, open doors, or even openings at the bottom of doors that allow air to flow in and out, 

as mentioned above, the actual asphyxiation risk to consumers is likely to be smaller than modeled. 

For the Asphyxiation Threshold Scenario, the room size at which an asphyxiation concern would exist 

(i.e., when the oxygen concentration in the lower 0.4 meters of the room is 12 percent) was determined. 

For asphyxiation to be of concern with the maximum charge size of 150 grams, the volume of the food 

preparation area would have to be about 1.0 m

3

(36.6 ft3) (see Threshold Analysis 2 in Table 7). Based on 

the worst-case modeling results and threshold analysis, EPA does not believe that the use of R-441A in 

commercial freezers poses a significant risk of asphyxiation or impaired coordination to personnel.

9. END-USE EXPOSURE ASSESSMENT

 

7 Twelve percent oxygen in air is the No Observed Adverse Effect Level (NOAEL) for hypoxia (ICF 1997).
May 30, 2014 -- Final

11

This section presents estimates of potential end-user exposures to R-441A and each of its chemical 

constituents in the event of a catastrophic release from the proposed substitute’s use in retail food 

refrigeration. An end-use exposure analysis was performed to examine potential catastrophic releases of

R-441A under the reasonable worst-case scenario outlined in Section 5.

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

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

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

from catastrophic leakage of refrigerant from commercial freezers were examined. The analysis was 

undertaken to determine the 30-minute exposures for each component of R-441A, which were then 

compared to the standard toxicity limits presented in Table 4 to assess the risk to end-users. However, the 

TWA values are fairly conservative as the analysis does not consider opened windows, fans operating, 

conditioned airflow (either heated or cooled) and other variables that would reduce the levels to which 

individuals would be exposed.

Table 8. End-Use Exposure Assessmenta

R-441A Component 30-minute TWA End-Use 

Exposure (ppm)

Short-term (30-min) Exposure 

Limits (ppm)b

Propane 4,390 6,900

n-Butane 2,180 6,900

Isobutane 360 6,900

Ethane 350 NA

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

b See Table 4 for more information.

Under the reasonable worst-case scenario described in Section 5, catastrophic releases of R-441A from a 

commercial freezer with a charge size of 150 grams was modeled. For a charge size of 150 grams, the 

estimated 30-min TWA exposures of the components of R-441A do not exceed 64 percent of the 

respective STELs. As such, use of R-441A in commercial freezers is not anticipated to present a 

significant risk to end-users. Furthermore, these exposures were derived using fairly conservative 

assumptions (e.g., minimum room volume, low ventilation rate [1.5 ACH], maximum charge size) that do 

not necessarily reflect the typical location for R-441A retail food refrigeration equipment installations 

(e.g., retail food refrigeration equipment will be installed in large food and drink establishments and 

supermarkets [A.S. Trust & Holdings, Inc. 2012]). To prevent exposure and potential serious side effects 

during larger releases, EPA proposes that the charge size for an R-441A commercial refrigeration unit to 

require compliance with UL 471 in any space containing a commercial refrigeration unit, unless proper 

leak protection devises are in place in order to prevent exposures of isobutane beyond the recommended 

limits. Proper leak protection devices and engineering control requirements and adherence to the MSDS 

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, installation, servicing, and 

disposal of R-441A. As indicated by the submitter, the manufacture of R-441A refrigerant (i.e., 

formulation mixing) and the charging of R-441A retail food refrigeration equipment (receiving, blending. 

and filling operations) occurs in a closed system; all units are completely sealed before delivery and 

installation. As a result, exposure during these manufacturing and installation operations is not 

anticipated. 

To ensure that use of the proposed substitute in retail food refrigeration does not pose an unacceptable 

risk to workers during servicing and disposal, occupational exposure modeling was performed using a 

box-model approach. For a detailed description of the methodology used for this screening assessment, 
May 30, 2014 -- Final

12

the reader is referred the occupational exposure and hazard analysis described in Chapter 5 of the 

Background Document. Estimates of refrigerant release per event for various release scenarios and data 

on number of events in 2010 were obtained from the Vintaging Model.8 To determine the estimated level 

of occupational exposure for a constituent in a blend, the total anticipated release rate of the refrigerant is 

multiplied by the weight percent composition of each compound in the blend. For the retail food 

refrigeration end use, the release per event was conservatively assumed to be 0.25 percent of the 

equipment charge during servicing and 35 percent of the equipment charge during disposal.9 Additionally, 

EPA is proposing to allow intentional venting or release of R-441A as a refrigerant during installation, 

servicing, maintenance and disposal from stand-alone retail food refrigeration equipment. If venting does 

occur, EPA recommends that it is done in a well-ventilated area (i.e. outdoors). Therefore, scenarios in 

which 100 percent of the equipment charge was released during servicing and disposal were also 

considered. The release rate per event was multiplied by the number of events estimated to occur over a 

workday. For equipment servicing, the number of events per workday was assumed to equal the 

maximum number of units anticipated to be serviced in one day (i.e., eight units [A.S. Trust & Holdings, 

Inc. 2011]) divided by eight hours per workday. These assumptions result in approximately 1 event per 

hour. For disposal, it was conservatively assumed that 10 units are disposed during an 8-hour work day. 

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

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

10.1 Occupational Exposure at Servicing

As indicated by the submitter, when R-441A retail food refrigeration equipment is serviced, the used 

refrigerant is pumped into a canister, where it is stored until it is recycled (i.e., filtered and reused) (A.S. 

Trust & Holdings, Inc. 2011). During the transfer to the initial canister, incidental refrigerant releases may 

occur during connection and disconnection of the recharging hose fittings, which should last 

approximately 30 seconds per unit (A.S. Trust & Holdings, Inc. 2011). 

The maximum 30-minute time weighted average (TWA) exposure for each R-441A constituent were 

estimated for the servicing exposure scenario and compared to their respective short term exposure limits

(see Table 9). The modeling results indicate that the maximum anticipated occupational exposure 

concentrations at no point exceed 0.3 percent of the short-term exposure limits for retail food refrigeration 

units with a 150-gram charge size during the 0.25 percent or 100 percent release scenarios. Because the 

exposure concentrations modeled under the conservative assumptions is significantly lower than the 

exposure limits for each constituent, occupational exposure to the proposed substitute during servicing is 

not considered a significant risk to workers. Further, the estimated 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.

 

8

ICF International maintains the Vintaging Model for EPA in order to simulate the aggregate impacts of the ODS phaseout on 

the use and emissions of various ODS and their substitutes over a period of several years across 60 different end-uses. The 

model tracks the use and emissions of various compounds for the annual vintages of new equipment that enter service in each 

end-use. The vintage of each type of equipment determines such factors as leak rate, charge size, number of units in operation, 

and the initial ODS substance that the equipment contained. 

9 During servicing and disposal it is assumed that 100 percent of the refrigerant charge remains in the unit.
May 30, 2014 -- Final

13

Table 9. Occupational Risk Assessment at Servicinga

R-441A 

Component

30-minute TWA Occupational Exposure (ppm) 30-min Short Term Exposure 

0.25% Release 100% Release Limits (ppm)

Propane 0.05 19.2 6,900b

n-Butane 0.02 9.6 6,900b

Ethane 0.004 1.5 3,000c

Isobutane 0.004 1.6 6,900b

a Cells highlighted in green are the scenarios that are deemed to be acceptable given various modeling assumption options.

b 30 min AEGL-1

c ACGIH (2004)

10.2 Occupational Exposure at Disposal

Disposal of R-441A retail food refrigeration equipment 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 refrigerant charge. Potential exposures to the refrigerant during recovery and disposal are expected to 

occur during activities related to draining the refrigerant from the refrigeration units into cylinders (e.g., 

connecting of pipes). Such activities and related exposure is anticipated to occur within 15-30 minutes 

(per event/day).

Table 10 displays the maximum estimated 8-hour TWA occupational exposure levels of the components 

of R-441A during disposal. Based on the assumptions described in the beginning of Section 10, the 

modeling indicates that 8-hour worker exposure concentrations for each of the R-441A blend components 

will at no point exceed 23 percent of their respective long-term exposure limits during disposal of R-441A

for retail food refrigeration units with a 150 gram charge size during the 35 percent and 100 percent 

release scenarios. Table 10 displays the maximum estimated 8-hour TWA occupational exposure levels of 

the R-441A constituents during disposal. Because each value is significantly lower than the exposure 

guidelines for each constituent, occupational exposure to the proposed substitute during disposal is not 

considered a toxicity threat. Further, 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 disposed of by trained personnel using proper industrial hygiene techniques.

Table 10. Occupational Risk Assessment at Disposala

R-441A Component

8-Hour TWA Occupational Exposure 

(ppm) 8-Hour Long Term Exposure 

Limits (ppm) 35% Release 100% Release

Propane 81.7 233.3 1,000b

n-Butane 40.6 115.9 1,000c

Ethane 6.5 18.7 1,000c

Isobutane 6.8 19.3 1,000c

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

b OSHA PEL

 c ACGIH TLV

Although anticipated occupational exposures are well below the exposure limits for each of the 

components of R-441A, the recommendations for proper engineering controls and PPE in the MSDS for 

R-441A should be followed. Adequate ventilation should always be established during any use, handling, 

or storage of R-441A. Engineering controls should include vapor-in air detection systems and local 

exhaust ventilation during use of R-441A to prevent dispersion throughout the work place. In addition, an 

eye wash and safety shower should be near the manufacturing facility and locations where R-441A is 

stored and ready for use. In general, use of OSHA Category B or higher PPE is recommended, such as 

splash goggles, mechanically-resistance gloves when handling cylinders and chemically-resistant gloves 

when handling the gas mixture (e.g., butyl rubber, chlorinated polyethylene, or neoprene). SCBA and fire 
May 30, 2014 -- Final

14

retardant protective clothing should be worn in case of an accidental release or spill (A.S. Trust & 

Holdings, Inc. 2011). EPA believes that if proper handling and disposal guidelines are followed in 

accordance with good industrial hygiene and manufacturing practices and the MSDS for R-441A, there is 

no significant risk to workers during the manufacturing, installation, servicing, and disposal of R-441A in 

retail food refrigeration units.

11. GENERAL POPULATION EXPOSURE ASSESSMENT

R-441A is not expected to cause a threat to human health in the general population when manufactured 

for use and used as a refrigerant in retail food refrigeration. The proposed substitute will be manufactured 

in a closed process and is proposed for use in closed systems, and thus, significant releases are not 

anticipated. At room temperature, R-441A is a gas and, therefore, releases to ground or surface water are 

not anticipated, as R-441A is anticipated to dissipate into the atmosphere upon release to outside air (i.e., 

because natural ventilation rates would be higher and there is no enclosed space to keep R-441A 

concentrated). Should air releases during manufacturing operations occur, engineering controls should be 

used (e.g. carbon absorption scrubbers) to collect R-441A and prevent the release of R-441A to the 

atmosphere. EPA believes that by using proper engineering controls and by following disposal and 

containment recommendations outlined in the proposed substitute’s MSDS, exposure to R-441A is not 

expected to pose a significant toxicity risk to the general population. 
May 30, 2014 -- Final

15

12. REFERENCES

Armines. 2009. Inventory of Direct and Indirect GHG Emissions from Stationary Air Conditioning and

Refrigeration Sources, with Special Emphasis on Retail Food Refrigeration and Unitary Air Conditioning. 

CARB Agreement No. 06-325.

ACGIH. 2012. Guide to Occupational Exposure Values. American Conference of Governmental 

Industrial Hygienists.

ANSI/ASHRAE. 2010a. Standard 15: Safety Standard for Refrigeration Systems. American Society of 

Heating, Refrigerating and Air-Conditioning Engineers, Inc.

ANSI/ASHRAE. 2010b. Standard 34: Designation and Safety Classification of Refrigerants. American 

Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 

ANSI/ASHRAE. 2013a. Standard 62: Ventilation for Acceptable Indoor Air Quality. American Society 

of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

A.S. Trust & Holdings, Inc. 2012. HCR-188C/R-441A for Use in New Commercial Refrigerators, 

Commercial Freezers and Stand-Alone Refrigerated Display Cases. Significant New Alternatives Policy 

Program Submission to the United States Environmental Protection Agency. March 2012. 

Braker W, Mossman AL. 1980. Matheson gas data book. 6th ed. Secaucus, NJ: Matheson Gas Products, 

pp. 615623. 

U.S. EPA 1994. Significant New Alternatives Policy Technical Background Document: Risk Screen on 

the Use of Substitutes for Class I Ozone-depleting Substances: Refrigeration and Air Conditioning. 

Stratospheric Protection Division. March, 1994.

Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. 

Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland. 2007. Changes in 

Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007:The Physical Science 

Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel 

on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and 

H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

ICF. 1997. Physiological Effects of Alternative Fire Protection Agents - Hypoxic Atmospheres 

Conference. Stephanie Skaggs prepared the proceedings of the conference held May 22, 1997 in New 

London, CT.

IPCC/TEAP. 2005. Bert Metz, Lambert Kuijpers, Susan Solomon, Stephen O. Andersen, Ogunlade 

Davidson, José Pons, David de Jager, Tahl Kestin, Martin Manning, and Leo Meyer (Eds). Safeguarding 

the Ozone Layer and the Global Climate System. Intergovernmental Panel on climate Change 

Technology and Economic Assessment Panel. Cambridge University Press, UK. pp 478.

Kataoka, O., M. Yoshizawa, & T. Hirakawa 2000. “Allowable Charge Limit of Flammable Refrigerants 

and Ventilation Requirements.” Daikin Industries. International Refrigeration and Air Conditioning 

Conference. Paper 506. Available online at: http://docs.lib.purdue.edu/iracc/506.

Mackenzie, F.T. and J.A. Mackenzie. 1995. Our changing planet. Prentice-Hall.

NFPA. 2014. NFPA Liquified Petroleum Gas Code. 2014 Edition.
May 30, 2014 -- Final

16

OSHA. 2004. “Safety and Health Topics: Isobutane.” February 2004. Available online at: 

<http://www.osha.gov/dts/chemicalsampling/data/CH_247840.html>.

Turk, B.H., D.T. Grimsrud, J.T. Brown, K.L. Geisling-Sobotka, J. Harrison, and R.J. Prill. 1989. 

“Commercial building ventilation rates and particle concentrations.” ASHRAE Transactions 95 (1): 422-

423. Paper No. 3248 presented at the 1989 meeting of the American Society of Heating, Refrigerating, 

and Air-Conditioning Engineers (ASHRAE), Chicago, Illinois. 

UL. 2010. UL 471: Commercial Refrigerators and Freezers. Underwriters Laboratory.

U.S. Department of Energy (DOE). 2008. DOE Handbook – Temporary Emergency Exposure Limits For 

Chemicals: Methods And Practice. Available online at: http://orise.orau.gov/emi/scapa/files/doe-hdbk1046-2008_ac.pdf.

U.S. EPA. 2012. Acute Exposure Guidelines (AEGLs) Definitions. Available online at: 

http://www.epa.gov/oppt/aegl/pubs/define.htm.

U.S. EPA. 2014. Draft Assessment of the Potential Impact of Hydrocarbon Refrigerants on Ground Level 

Ozone Concentrations. Prepared for the U.S. EPA Stratospheric Protection Division by ICF International. 

February 24, 2014.

WMO (World Meteorological Organization), 2011. Scientific Assessment of Ozone Depletion: 2010, 

Global Ozone Research and Monitoring Project-Report No. 52, 516 pp., Geneva, Switzerland.