May 30, 2014 -- Final

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Significant New Alternatives Policy Program 

Refrigeration and Air Conditioning Sector

Risk Screen on Substitutes for HCFC-22 in Residential and Light Commercial Air 

Conditioning and Heat Pumps

Substitute: R-441A

This risk screen is restricted to residential and light commercial window air conditioner 

applications and other self-contained room air conditioners meeting the requirements of UL 484: 

Room Air Conditioners.

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 HCFC-22 in the residential and light commercial 

air conditioning (AC) and heat pump end-use that meets the requirement of Underwriters Laboratory 

(UL) Standard 484: Room Air Conditioners, specifically in window AC units, packaged terminal AC 

(PTAC), packaged terminal heat pumps (PTHP), and portable AC units. Table 1 details 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.
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Section 2 of this report summarizes the results of the risk screen for the proposed substitute blend listed in 

Error! Reference source not found.. The remainder of the report is organized into the following 

sections:

 Section 3: Atmospheric Assessment

 Section 4: Volatile Organic Compound Assessment 

 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

R-441A is recommended for SNAP approval for residential and light commercial room AC units that 

comply with Underwriters Laboratory (UL) Standard 484: Room Air Conditioners, specifically window 

AC units, packaged terminal AC (PTAC), packaged terminal heat pumps (PTHP), and portable AC units.

EPA's risk screen indicates that the use of the proposed substitute and its constituents will be less harmful 

to the atmosphere than the continued use of HCFC-22 as it is less harmful to the ozone layer, has lower 

climate impact, and a shorter atmospheric lifetime. No significant asphyxiation risks to consumers or 

toxicity risks to workers, consumers, or the general population are expected. Three of the four 

components of R-441A 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 groundlevel ozone concentrations, VOC emissions from the use of R-441A in window air conditioners are not 

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

expected that procedures identified in the MSDS for R-441A and good manufacturing practices will be 

adhered to, and 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 & Health Administration (OSHA)

guidelines will be used during manufacture, installation, servicing, and disposal of room AC systems 

using R-441A. Because units are to be installed in locations with adequate space or ventilation in 

accordance with the AC maintenance manual for R-441A window AC units, as discussed in greater detail 

in Section 9, 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 AirConditioning Engineers (ASHRAE) Standards 15,

1

34,2and 62,3and Underwriters Laboratories (UL)

Standard 484.4

 

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 484 Standard for Safety: Room Air Conditioners establishes safety requirements for room air conditioners that are designed 

to provide delivery of conditioned air to an enclosed space, room, or zone. 
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3. ATMOSPHERIC ASSESSMENT

This section presents an assessment of the potential risks to the atmosphere posed by the use of R-441A

in window AC units. 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 compared to 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 a commonly utilized substitute, R-410A. Thus, EPA believes that 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, such as HCFC-22 and R-410A. 

Table 2. Atmospheric Impacts of R-441A Components Compared to HCFC-22 and R-410A

Refrigerant Ozone Depleting 

Potential (ODP)

Global Warming Potential 

– 100 year (GWP)

a

Atmospheric Lifetime in 

Years (ALT)

Propane 0 3.3 0.03b

n-Butane 0 4.0 0.018c

Isobutane 0 ~4 0.016b

Ethane 0 5.5 0.21c

HCFC-22 0.13b 1,810 12a

R-410Ad 0 2,088 NAe

NA = not applicable

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

b WMO (2011) 

c

IPCC/TEAP (2005)

d R-410A is a blend of 50% HFC-32 and 50% HFC-125.

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]).

4. VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS

Propane, isobutane and n-butane are regulated as VOCs under the CAA, while ethane is exempted (40 

CFR 51.100 [s]). Through regulations and standard industry practices, VOC emissions 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 5under 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 in the evaluation 

included residential AC units (e.g., window units, PTAC/PTHP), 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, 

 

5 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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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 less 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. 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 window AC units are not anticipated to contribute significantly to 

ground level ozone concentrations in the United States.

5. DISCUSSION OF END-USE SCENARIOS MODELED

R-441A is proposed for use in residential and light commercial room AC units. The remainder of this risk 

screen assesses the risk of window AC units. To represent a reasonable worst-case scenario, it was

assumed that the full charge of the window AC unit is emitted over the course of one minute into a 

bedroom, where it is located. Because window AC units can be installed in a wide range of locations with 

varying room volumes, the analysis in this risk screen conservatively assumes that the window air 

conditioner is located in a bedroom with a volume of 41 m

3

(1,450 ft3). Under EPA’s proposed charge 

size limits, which correspond to those found in UL 484, the maximum refrigerant charge allowed for R441A window AC units installed in a room of 41m3

(1,450 ft3) is 195 grams. 6 However, the submission 

states that R-441A window AC units will have a typical charge size of 125 grams. Furthermore, UL 

Standard 484 indicates that the maximum charge size of a window AC unit containing a flammable 

refrigerant is 1,000 grams. Therefore, this risk screen evaluates the risks associated with all three charge 

sizes.

This risk screen evaluates a bedroom with air exchange rates of 0.11 ACH and 0.67 ACH. The EPA 

Exposure Factors Handbook (1997) states that the typical residential air exchange rate is 0.45 ACH, 

which factors in tests from homes that are greater than 45 years old as well as those that are less than 10 

years old. However, older homes (i.e., built before 1994) are more likely to use window AC units than 

newer homes. Based on data of AC use in U.S. homes by year of construction, 27 percent of homes using 

AC equipment use window AC units, while the remaining use central air conditioning equipment (EIA 

2013). On average, 38 percent of homes built before 1990 use window AC units in comparison to the 

average of 9 percent of homes built after 1990. Air exchange rates are expected to be greater in older 

homes that are typically built with loose construction practices (e.g., no or inadequate effort to seal 

structural panels, corners, cracks, joints, and penetrations; window and door assemblies are not rated). 

Additionally, if a home uses window AC units, EPA does not expect that there is any significant 

mechanical ventilation present in the home.

During the cooling season (May to September), air changes per hour in spaces with a floor area of 900 

square feet or less are reported to be between 0.11 ACH for tight construction and 0.67 ACH for loose 

construction (ACCA 2006). Therefore, this risk screen models both air exchange rates, 0.11 ACH and 

0.67 ACH, in order to account for installation of units in homes with different construction practices, for 

all three charge sizes (125 grams, 195 grams, and 1,000 grams).

It is further assumed that an individual is present at the start of the leak and remains in the room until the 

 

6 Under EPA’s proposed limits, for a conservative room of 41m3

, the appropriate cooling capacity would be approximately 6,500 

BTU/hr, corresponding to an associated charge size limit of 195 grams.
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charge is completely released. UL 484 assumes that window AC units and their compressors are installed 

at a height of 1 meter above the ground. Based on this location and because R-441A is denser than air 

(specific gravity of R-441A relative to air is 1.67 [air = 1]), this risk screen assumes that a vertical 

concentration gradient of R-441A will occur. In order to simulate the vertical concentration gradient, it is 

assumed that 95 percent of the leaked refrigerant mixes evenly into the lower 1 meter of the room, and the 

rest of the refrigerant mixes evenly in the remaining volume (Kataoka 2000). Modeling of the lower 1 

meter of the room is consistent with the possibility that, in a bedroom scenario, individuals may be lying 

close to the floor. Table 3 details the assumptions used in the models throughout this risk screen (i.e., in 

Sections 7, 8, and 9).

Table 3. End-Use Scenario Model Assumptions

Parameter Assumption

Room Type Bedroom

Size (m3) 41a (1,450 ft3)

Ventilation Rate (air changes per hour) 0.11b; 0.67c

Air Conditioning Unit Window AC

Charge Size (g) 125d; 195

e

; 1,000f

Length of Release (minutes) 1

Vertical Concentration Gradient Yes

a Background Document (EPA 1994)

b Tight construction home (ACCA 2006)

c Loose construction home (ACCA 2006)

d Maximum charge size for a window AC under EPA’s proposed use conditions., based on a room size of 41 m3, and 

capacity of 6500 BTU/hr.

e Typical charge size (A.S. Trust & Holdings, Inc. 2012).

f Maximum charge size for a window AC unit under UL 484.

6. POTENTIAL HEALTH EFFECTS

To assess potential health risks from exposure to the proposed substitute in window AC units, EPA 

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

different scenarios for each constituent of R-441A. 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” to ensure that there is not a significant risk of toxicity, asphyxiation, 

and flammability (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). Potential short-term, end-use exposures are 

compared to an established short-term exposure limit (STEL), acute exposure guideline level (AEGL), or 

emergency response planning guideline (ERPG); in the absence of these limits, an excursion limit, 
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calculated according to the methodology described in ACGIH (2004), is applied.7 When evaluating the 

toxicity of R-441A, the cumulative effects and additivity of toxicities of short-chain aliphatic 

hydrocarbons are not considered to be a concern. ACGIH and OSHA do not consider these cumulative 

risks. Furthermore, a recent study evaluated alkane gases (ethane, propane, n-butane, and isobutane) in 

combined repeated exposure studies with reproduction/development toxicity screening tests. No 

significant effects on systemic toxicity or neurotoxicity were found at concentrations from 9,000 to 

16,000 ppm, and no significant effects on developmental or reproductive toxicity were found at the 

highest concentrations tested (McKee RH et. al. 2013). Furthermore, the components of R-441A do not 

share an end-point of concern. 

Table 4 lists the relevant toxicity limits of R-441A components, 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 R-441A Components

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 5. Explanation of Exposure Limit-Related Terminology a

 

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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.

R-441A 

Component

8-hr WGL (Long-term 

Exposure)

ppm

30-min 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

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
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Short-Term Exposure

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

time during a workday, even if the 8-hour TWA is 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, set by EPA. 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, set by EPA.

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 lifethreatening health effects or death, set by EPA.

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 

escape-impairing or irreversible health effects, as indicated by 

NIOSH.

TEELe

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 set by DOE. 

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 set by DOE.

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 set by 
May 30, 2014 -- Final

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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)

e Chemical exposure guidelines to use for emergency planning if no AEGL or ERPG is available. TEELs are developed based on concentration 

limits or toxicology parameters (DOE 2008).

According to the 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 soap and 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 of R-441A to the eyes could cause eye irritation. In case of ocular exposure, the MSDS for R441A 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 to 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 manufacturing, servicing, and end-use. 

DOE. 

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. 
May 30, 2014 -- Final

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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 window air conditioners occurs in a closed system. As a result, releases of R-441A 

during manufacturing 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. 

It is important that all relevant standards be followed during the manufacture of window air conditioners. 

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 part 

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 R-441A.

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 R-441A. Both servicing and end-use of R-441A window AC units 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, modeled 

concentrations of R-441A immediately following the release of refrigerant were compared to the LFL for 

R-441A. As demonstrated in 

Table, the maximum instantaneous concentration in the lower 1 meter of the room at a charge size of 125 

grams would be approximately 3,450ppm, approximately 5,390 ppm for a 195-gram charge size, and 

approximately 27,620 ppm for a 1,000-gram charge size. The 125-gram charge size indicated by the 

submitter (Reasonable Worst-Case 1) and the 195-gram charge size proposed by EPA (Reasonable 

Worst-Case 2) do not present a significant flammability concern. In contrast, the scenario using a 1,000-

gram charge size (Reasonable Worst-Case 3) exceeds the proposed substitute’s LFL of 20,500 ppm.

However, according to UL 484, a window unit with a charge size of 1,000 grams in not intended for 

installation in a room with a volume as small as that modeled in the worst-case scenario (41 m3). The 

minimum room size for a charge size of 125 grams according to UL 484 is approximately 18 m3(630 

ft3), assuming a 2.4 m ceiling height, and the maximum charge size for a 41 m3(1,450 ft3) room according 

to UL 484 is approximately 195 grams. 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, and this area has greater volume than the lower 1 meter. EPA is also proposing to 
May 30, 2014 -- Final

10

limit charge sizes that an equipment manufacturer may use for a given cooling capacity. The appropriate 

cooling capacity for a room of 41 m3 would be approximately 6,500 BTU/hr, with an associated charge 

limit of 195 grams under EPA’s proposed use conditions. The results of the flammability assessment are 

presented in Table 6. 

Table 6. Flammability Assessmenta

Scenario Charge Size (g) Effective Room 

Size (m3)

Maximum Instantaneous 

Concentration

(ppm) b,c

Reasonable Worst-Case 1 125 41 (1,450 ft3) 3,450

Reasonable Worse-Case 2 195 41 (1,450 ft3) 5,390

Reasonable Worst-Case 3 1,000 41 (1,450 ft3) 27,620

Threshold Analysis 1: Charge Size 742 41 (1,450 ft3)

20,500 Threshold Analysis 2a: Room Size 125 7 (244 ft3

)

Threshold Analysis 2b: Room Size 195 11 (380 ft3)

Threshold Analysis 2c: Room Size 1,000 55 (1,950 ft3)

Bold font indicates modeling results.

a Cells highlighted in green are the scenarios with acceptable exposure levels 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 1 meter of the room.

For the Flammability Threshold analysis shown in Table 6, the conditions at which a flammability 

concern would exist (i.e., when the maximum instantaneous concentration in the lower 1 meter of the 

room equals the LFL for R-441A) were determined. Within the reasonable worst-case room size of 41 m3

(1,450 ft3), the charge size of the R-441A window AC would have to be at least 742 grams (see Threshold 

Analysis 1 in Table 6) for a flammability concern to exist, which is approximately 5.9 times larger than 

the largest size intended by the submitter (i.e., 125 grams) and approximately 3.8 times larger than EPA’s 

recommended charge size (i.e., 195 grams) for R-441A window AC units. For window AC units with a 

charge size of 125 grams (see Threshold Analysis 2a in Table 6) the volume of the bedroom would have 

to be 7 m3(244 ft3) or smaller for a flammability risk to occur. For window AC units with a charge size of

195-grams (see Threshold Analysis 2b in Table 6) the volume of the room would have to be 11 m

3

(380

ft3) or smaller for a flammability risk to occur. Using a charge size of 1,000-grams for window AC units

(see Threshold Analysis 2c in Table 6) the volume of the bedroom would have to be 55 m

3

(1,950 ft3) or 

smaller for a flammability risk to occur. 

According to the results of this flammability analysis, the risk of fire is minimal if a window AC unit is 

installed in a room with volumes in accordance with standards and regulations. As bedrooms can be of 

smaller sizes,8and because persons or furniture in the room may reduce the effective volume of the space, 

window AC units containing R-441A should not be installed in rooms with effective volumes less than 

 

8

International Residential Code requires a minimum of 70 ft2for a habitable room, or 14 m3(490 ft3) (ICC 2012).
May 30, 2014 -- Final

11

what UL 484 indicates with respect to charge size, unless additional steps are taken to protect against a 

flammability risk (e.g., higher ventilation rates). According to UL 484 and assuming a mounting height of 

1 meter, R-441A window AC units with charge sizes of 125 grams, 195 grams, and 1,000 grams should 

not be installed in a room less than 17 m

3

(610 ft3), 41 m

3

(1,450 ft3) and 1,332 m3 (47,000 ft3) , 

respectively. In addition, EPA recommends that the ventilation requirements outlined in the MSDS for R441A are followed to mitigate the risk of fire or explosion during catastrophic leak during end-use or 

when servicing equipment using R-441A. 

It is also 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, although considered rare, since this type of equipment is hermetically sealed 

and is often replaced rather than serviced if the charge leaks, 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. 

The installation of leak prevention devices would further protect against the very limited risk of 

explosion. When the guidelines recommended by EPA and industry standards including UL 484 are 

followed, EPA does not believe that use of R-441A in window AC units presents a significant risk of 

flammability at servicing or end-use.

8. ASPHYXIATION ASSESSMENT

The risk of asphyxiation for the reasonable worst-case scenario (see Section 5) was investigated for R441A. 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 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, this 

analysis 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)b

Effective Room Size 

(m3)

Percent Oxygen 

Concentration in Lower 1 

Meter

Reasonable Worst-Case 1 125 41 (1,450 ft3

) 21

Reasonable Worst-Case 2 195 41 (1,450 ft3

) 21

Reasonable Worst-Case 3 1,000 41 (1,450 ft3

) 21

Threshold Analysis 1: Charge Size 18,520 41 (1,450 ft3

) 12

Threshold Analysis 2a: Room Size 125 0.28 (9.8 ft3

) 12

Threshold Analysis 2b: Room Size 195 0.43 (15.2 ft3

) 12

Threshold Analysis 2c: Room Size 1,000 2.2 (78.2 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)
May 30, 2014 -- Final

12

Under the reasonable, worst-case scenario (see Reasonable Worst-Case 1 and Reasonable Worst-Case 2 

in Table 7), an asphyxiation risk will not occur, as the oxygen concentration in the room is 21 percent, 

well above the 12 percent level of concern.9 The concentration of R-441A in the air in the lower 1 meter

of the room following the release of the maximum charge size of 1,000 grams does not exceed 2.3

percent, which has an insignificant impact on the normal concentration of oxygen in air. This 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, 

therefore, the actual asphyxiation risk to personnel 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. Within the reasonable worst-case room size of 41 m3(1,450 ft3) 

(see Threshold Analysis 1 in Table 7) the charge size of the R-441A AC unit would have to be at least 

18,520 grams for asphyxiation to be a concern, which is more than 18 times the largest charge size 

allowed for R-441A window AC units according to UL 484 (i.e., 1,000 grams). For asphyxiation to be of 

concern with a 125-gram R-441A window AC unit (see Threshold Analysis 2a in Table 7) the volume of 

the bedroom would have to be 0.28 m

3 (9.8 ft3

). Using a 195-gram window AC unit, as shown under 

Threshold Analysis 2b, the volume of the room would have to be 0.43 m

3 (15.2 ft3

) or smaller for 

asphyxiation to be of concern. Using a 1,000-gram R-441A window AC unit (see Threshold Analysis 2c

in Table 7) the volume of the bedroom would have to be 2.2 m

3 (78.2 ft3

) for asphyxiation to be a concern, 

which is significantly smaller than the reasonable worst-case bedroom size (41 m3[1,450 ft3]). In 

addition, the threshold room volumes at which asphyxiation could occur during a catastrophic leak of a 

125-gram, 195-gram or 1,000-gram unit are smaller than the minimum bedroom volume typically found 

in the U.S. 10

To further protect against an asphyxiation risk, end-users should ensure window AC units are installed 

with an appropriate cooling capacity for the intended cooled space to be consistent with manufacturer 

recommendations and the guidelines of relevant safety standards (e.g., ASHRAE 15 and UL 484). Leak 

prevention, detection, or mitigation devices should be installed and the ventilation requirements outlined 

in the MSDS for R-441A should be closely followed. If these guidelines are followed, a catastrophic leak 

of R-441A is not anticipated to result in a significant asphyxiation risk. 

9. END-USE EXPOSURE ASSESSMENT

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

constituents in window AC units. An exposure analysis was performed to examine potential catastrophic 

release of the proposed substitute in a bedroom under the reasonable worst-case scenario outlined in 

Section 5 with a charge size of 125 grams, 195 grams, and 1,000 grams. 

For the end-use exposure assessment scenario, 30-minute time-weighted average (TWA) exposures for 

the constituents of 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. 

These exposures were then compared to the standard toxicity limit presented in Table 4 to assess the risk 

to end-users. The results of the assessment provide both fairly conservative and more realistic TWA 

values, as the analyses using both a 0.11 ACH and a 0.67 ACH ventilation rate do 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. Modeling was performed for all constituents of 

R-441A, however, only the results for propane, which show the end-use exposure levels under the 

reasonable worst-case scenario in Section 4, are presented in Table 8. As the primary component of R441A, propane presents the greatest risk of exceeding the STEL and thus the most conservative 

 

9 Twelve percent oxygen in air is the NOAEL for hypoxia (ICF 1997). 

10 The 2012 International Residential Code requires bedrooms to have a minimum volume of 13.9 m3

(490 ft3) (ICR ICC 2012). 
May 30, 2014 -- Final

13

assessment. 

Table 8. End-Use Exposure Assessment of R-441A Propane Componenta

Scenario Charge Size (g) Effective Room 

Size (m3)

Air Exchange 

Rate (ACH)

30-minute TWA 

End-Use Exposure 

(ppm)b, c

Reasonable Worst-Case 1a

125

41 (1,450 ft3)

0.11 2,028

Reasonable Worst-Case 1b 0.67 1,785

Reasonable Worst-Case 2a 195

0.11 3,163

Reasonable Worst-Case 2b 0.67 2,784

Reasonable Worst-Case 3a 1,000 0.11 16,223

Reasonable Worst-Case 3b 0.67 14,277

Threshold Analysis 1a: Charge Size 425 41 (1,450 ft3

)

0.11

6,900

Threshold Analysis 1b: Charge Size 483 0.67

Threshold Analysis 2a: Room Size 125 12 (430 ft3) 0.11

Threshold Analysis 2b: Room Size 11 (370 ft3) 0.67

Threshold Analysis 3a: Room Size 195 19 (660 ft3) 0.11

Threshold Analysis 3b: Room Size 17 (580 ft3) 0.67

Threshold Analysis 4a: Room Size 1,000 96 (3,400 ft3) 0.11

Threshold Analysis 4b: Room Size 85 (3,000 ft3) 0.67

Threshold Analysis 5a: Air Exchange Rate 125

41 (1,450 ft3)

0

Threshold Analysis 5b: Air Exchange Rate 195 0

Threshold Analysis 5c: Air Exchange Rate 1,000 4.4

Bold font indicates modeling results.

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

b

30-min AEGL-1 STEL for propane is 6,900 ppm; See Table 4 for more information

c Values provided in this column refer to the concentration in the lower 1 meter of the room, which presents the most conservative risk as s 95 

percent of the leaked refrigerant in present in this space.

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

window AC unit with charge sizes of 125 grams, 195 grams, and 1,000 grams were modeled with two 

different air exchange rates, 0.11 ACH and 0.67 ACH. In Reasonable Worst-Case Scenarios 3a and 3b, 

which model a 1,000-gram charge size and ventilation rates of 0.11 ACH and 0.67 ACH respectively, the 

30-minute AEGL-1 for propane of 6,900 ppm is likely to be exceeded (see Table 8). However, the 30-min 

TWA exposures in Reasonable Worst-Case Scenarios 3a and 3b do not exceed the AEGL-2 (17,000 ppm) 

or the AEGL-3 (33,000 ppm) for propane.

A threshold analysis was performed to determine the charge size, minimum room volume, and ventilation 

rates where window AC units containing R-441A could be installed to avoid the STEL for each of the 

components of R-441A. Based on this end-use exposure threshold analysis, shown in Table 8, the 

maximum charge size that should be installed in a room of 41 m3(1,450 ft3) volume with 0.11 ACH is 

425 grams and 483 grams with 0.67 ACH (see Threshold Analysis 1a and 1b in Table 8). Additionally, 

the threshold analysis indicates that window AC units with charge sizes of 125 grams, 195 grams, and 

1,000 grams should not be installed in rooms smaller than 12 m3(430 ft3), 19 m

3

(660 ft3), and 96 m

3

(3,400 ft3), respectively, assuming an air ventilation rate of 0.11 ACH. As shown in Table 8, these 

recommended minimum rooms sizes are smaller if the ventilation rate is increased to 0.67 ACH.

Because a window AC units with a charge size of 1,000 grams was modeled in a room size that is much 

smaller than the size recommended by UL 484 in the reasonable worst-case scenarios, it is not unexpected 

that the calculated 30-minute TWA exposures for that scenario exceeds the AEGL-1 for propane. These 
May 30, 2014 -- Final

14

potential exposure exceedances emphasize the importance associated with proper equipment installation, 

(i.e. matching charge size with room dimensions). To prevent exposure and potential serious side effects 

during larger releases, EPA proposes the charge size for R-441A window AC units to require compliance 

with UL 484 and with proposed charge sizes based upon cooling capacity in the proposed rule. Smaller 

accidental releases of the proposed substitute, however, do not pose a significant risk to end-users. Thus, 

risk of toxicological threat is minimal if a window AC unit is installed in a room with volumes in 

accordance with standards and regulations and/or in enclosed areas with volumes larger than those 

determined in the threshold analyses. Furthermore, proper ventilation should be used in accordance with 

the MSDS for R-441A. When these conditions are met, accidental catastrophic releases of the proposed 

substitute would not pose a significant risk to end-users. 

10. OCCUPATIONAL EXPOSURE ASSESSMENT

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

disposal of R-441A in window AC units. As indicated by the submitter, all manufacturing steps will be 

conducted in closed systems appropriately constructed for safety and elimination of environmental 

releases and worker exposures. Standard operating procedures and personnel training focus on 

minimizing such releases and occupational exposures. As a result, exposure to R-441A during 

manufacturing is not anticipated and is not analyzed further.

To ensure that use of the proposed substitute in window AC units does not pose an unacceptable risk to 

workers during servicing and disposal, occupational exposure modeling was performed using a boxmodel approach. For a detailed description of the methodology used for this screening assessment, 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 were obtained from the Vintaging Model.11 To determine the estimated level of 

occupational exposure for a constituent in the proposed substitute blend, the total anticipated release rate 

of the refrigerant is multiplied by the weight percent composition of each compound in the blend. For the 

window AC unit end use, the release per event was conservatively assumed to be 0.4 percent of the 

equipment charge during installation and servicing and 50 percent of the equipment charge during 

disposal.12 Additionally, EPA is proposing to allow intentional venting or release of R-441A as a 

refrigerant during installation, servicing, maintenance and disposal from window AC units. If venting 

does occur, it should be done in a well-ventilated area (e.g., 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. 2012]) 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. 

10.1 Occupational Exposure at Installation and Servicing 

Window AC units are expected to be serviced rarely, since this type of equipment is hermetically sealed. 

Generally, in the U.S., these units are replaced rather than serviced if the charge leaks. Nevertheless, the 

potential occupational exposure for those situations where servicing takes place was analyzed. The 

 

11 ICF International maintains the Vintaging Model for EPA in order to simulate the aggregate impacts of the ODS phase-out 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. The service leak rate and disposal release rate assumptions are 

consistent with the window AC end-use in Vintaging Model version VM IO file_v4.4_11.6.12. 

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

15

possibility of a release during installation was also considered. The maximum 30-minute time-weighted 

average (TWA) exposure for each component in R-441A was estimated for servicing window AC units 

charged with 125 grams, 195 grams, and 1,000 grams of R-441A. As summarized in Table 8, 

occupational exposure to R-441A is anticipated to be significantly below the short-term exposure limits 

(STEL) with either a 125-gram, 195-gram or 1,000-gram charge size and with a 0.4 percent or 100

percent release during installation and servicing. Installation and servicing activities for window ACs 

using R-441A are not expected to result in significant worker exposure when certified technicians follow 

the procedures outlined in the MSDS and maintenance manual, undergo proper training, and wear 

appropriate PPE (e.g., gloves and safety glasses). Adequate ventilation should always be established 

during any use, handling, or storage of R-441A. Systems should be installed to ensure leak-free 

conditions, for instance by following procedures of ASHRAE Standard 147 including conducting leak 

checks once a system is installed (ASHRAE 2013b). In addition, during servicing events, prior to adding 

refrigerant, all pipes should be inspected for leakages, and repairs should be performed only after all 

refrigerant has been recovered from the system. By adhering to the safety guidelines mentioned above, 

and in Section 6, worker exposure to R-441A during installation and maintenance is unlikely.

Table 9. Occupational Risk Assessment at Servicinga

R-441A 

Component

30-minute TWA 

Occupational Exposure 

(ppm)

Charge size: 125 grams

30-minute TWA 

Occupational Exposure 

(ppm)

Charge size: 195 grams

30-minute TWA 

Occupational Exposure 

(ppm)

Charge size: 1,000 

grams

30-min Short 

Term Exposure 

Limits (ppm)

0.4% 

Release

100% 

Release

0.4% 

Release

100% 

Release

0.4% 

Release

100% 

Release

Propane 0.60 150 0.86 214 4.8 1,200 6,900b

n-Butane 0.23 57 0.44 106 1.8 450 6,900b

Isobutane 0.04 9.5 0.07 18 0.30 76 6,900b

Ethane 0.07 18 0.07 17 0.60 150 3,000c

a

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

b AEGL-1; See Table 4 for more information

c ACGIH (2004)

10.2 Occupational Exposure at Disposal

Disposal of the R-441A window AC unit is expected to occur at disposal facilities with limited duration 

of exposure to the refrigerant. 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 R-441A 

constituents 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 

during the 50 percent release scenario will at no point exceed the long-term exposure limits of any of the 

individual components during disposal of R-441A for window AC units with a charge size of 125 grams, 

195 grams, or 1,000 grams. Under the 100 percent release scenario at disposal of the 1,000-gram window 

unit, the 8-hour TWA would be exceeded for the propane component of R-441A. However, occupational 

exposure to the proposed substitute during disposal does not represent a true occupational health hazard 

because the estimated exposure concentrations of the propane component of R-441A for all scenarios do 

not exceed the 8-hr AEGL-1 for propane, which is 5,500 ppm. Furthermore, these estimated exposures 

were derived using conservative assumptions (e.g., no ventilation or use of PPE assumed), and represent a 

reasonable 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.
May 30, 2014 -- Final

16

Table 10. Occupational Risk Assessment at Disposala

R-441A 

Component

8-Hour TWA 

Occupational Exposure 

(ppm)

Charge size: 125 grams

8-Hour TWA 

Occupational Exposure 

(ppm)

Charge size: 195 grams

8-Hour TWA 

Occupational 

Exposure (ppm)

Charge size: 1,000 

grams

8-Hour Long Term 

Exposure Limits 

(ppm)

50% 

Release

100% 

Release

50% 

Release

100% 

Release

50% 

Release

100% 

Release

Propane 130 270 190 379 1,060 2,100 1,000b

n-Butane 50 100 94 188 400 800 1,000c

Isobutane 8.4 17 16 31 67 130 1,000c

Ethane 16 32 15 30 130 260 1,000c

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

b OSHA PEL

c ACGIH TLV 

Because anticipated occupational exposures could potentially exceed the exposure limits for each of the 

components of R-441A during disposal of 1,000-gram window AC units without recovery, 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 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 retardant protective clothing should be worn in 

case of an accidental release or spill (A.S. Trust & Holdings, Inc. 2012). 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 window AC units.

11. GENERAL POPULATION EXPOSURE ASSESSMENT

R-441A is not expected to cause a concern for human health in the general population when used as a 

refrigerant in window AC units. 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 propane concentrated). Should air releases during manufacturing operations occur, including 

filling of AC units, engineering controls could be used (e.g., carbon absorption units or 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

17

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Edition.

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ACGIH. 2005. Guide to Occupational Exposure Values. American Conference of Governmental 

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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.

ANSI/ASHRAE. 2013b. Standard 147: Reducing the Release of Halogenated Refrigerants from 

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A.S. Trust & Holdings, Inc. 2012. HCR-188C/R-441A for Use in White Goods Systems. Significant 

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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 

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

ICC IRC. 2012. International Residential Code. International Code Consortium. 

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

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

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

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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.
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McKee R.H., D. Herron, M. Saperstein, P. Podhasky, G.M. Hoffman, & L. Roberts. 2013. The 

Toxicological Properties of Petroleum Gases. International Journal of Toxicology.

NFPA. 2014. NFPA Liquefied Petroleum Gas Code. 2014 Edition.

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

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