March 28, 2016 – Final 

1 

Significant New Alternatives Policy Program 

Refrigeration and Air Conditioning Sector 

Risk Screen on Substitutes in Residential and Light Commercial Air Conditioning and Heat 

Pumps 

Substitute: R-443A 

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-uses and applications within all of the major 

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

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

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

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

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

evaluates the potential use of R-443A as a substitute in the residential and light commercial air 

conditioning (AC) and heat pumps end-use (specifically window AC units, split-system AC units, 

residential heat pumps, and portable AC units). Table 1 presents the composition of the proposed 

substitute. 

Table 1. Composition of R-443A 

Constituent Chemical Formula CAS Number Concentration

(Weight Percent)a

Propylene C3H6 115-17-1 55% 

Propane C3H8 74-98-6 40% 

Isobutane C4H10 75-28-5 5% 

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 in Error! Reference 

source not found.. 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 

• Section 6: Potential Health Effects 

• Section 7: Flammability Assessment 

• Section 8: Asphyxiation Assessment 
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• 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-443A is not recommended for SNAP approval as a refrigerant in residential and light commercial AC 

units and heat pumps, specifically window AC units, split-system AC units, residential heat pumps, and

portable AC units. 

R-443A is regulated as a volatile organic compound (VOC) under CAA regulations (40 CFR 51.100(s)). 

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

concentrations, VOCs from the use of R-443A are anticipated to result in greater impacts on local air 

quality in the United States than other available options. 

According to the results of the assessments in this risk screen, significant flammability risk is unlikely (see 

Section 7 of this document). However, the results of the end-use exposure assessment indicate significant 

toxicity risk at end-use is likely even when units are installed in locations with adequate space or 

ventilation conditions in accordance with equipment maintenance manuals for R-443A residential and light 

commercial AC equipment (see Section 9 of this document). Toxicity risks at end-use exceed additional 

safeguards, including specified refrigerant concentration limits (RCL) of R-443A components, which are

provided by adherence to industry standards including American Society of Heating, Refrigerating and 

Air-Conditioning Engineers (ASHRAE) Standards 15,1

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

Standard 484.4

 Because of the potential local air quality impacts and toxicity risk posed by use of R-443A 

in the proposed end-uses, R-443A is not recommended for SNAP approval as a refrigerant in residential 

and light commercial AC units and heat pumps. 

3. ATMOSPHERIC ASSESSMENT 

This section presents an assessment of the potential risks to atmospheric integrity posed by the use of R443A in residential and light commercial AC and heat pumps. 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 ALT when compared to refrigerants such as CFC-12 and HCFC-22. In addition, R-443A also has 

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

Background Document as well as the commonly utilized refrigerant, R-410A. 

 

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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Table 2. Atmospheric Impacts of R-443A Components Compared to Other Refrigerants used in 

Residential and Light Commercial AC and Heat Pumps 

Refrigerant Ozone Depleting 

Potential (ODP)a

Global Warming Potential 

(GWP)b

Atmospheric Lifetime in 

Years (ALT) 

Propylene 0 1.8 0.35 daysb

Propane 0 3.3 0.03b

Isobutane 0 ~4 0.016b

CFC-12 0.82 10,900 100

HCFC-22 0.13b 1,810 12b

R-410Ac 0 2,088 NAd

NA - Not applicable 

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

b

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

c

 R-410A is a blend consisting of HFC-32 (50%), and HFC-125 (50%). 

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

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

4. VOLATILE ORGANIC COMPOUND (VOC) ANALYSIS 

The components of R-443A are regulated as VOCs under CAA regulations (40 CFR 51.100 [s]). 

Emissions of R-443A should be controlled according to CAA and other regulations by adhering to 

standard industry practices. EPA prepared a separate analysis in 20145 and a follow-on analysis in 20166 to 

evaluate the potential impact of the use of hydrocarbon refrigerants on ground-level ozone concentrations 

in the United States. 

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

were assumed to contain propylene, isobutane, and/or propane under different scenarios. The hydrocarbon 

emissions from these scenarios were estimated based on EPA’s Vintaging Model, and their potential 

contributions to ozone concentrations were assessed using EPA’s Community Multiscale Air Quality 

(CMAQ) model.7 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 analysis considers the propensity of organic compounds to form ozone according to their maximum 

incremental reactivity (MIR). The MIR scale assesses a compound’s contributions to the photochemical 

ozone formation in urban plumes and is reflective of its use in North America, where ground-level ozone 

formation is considered an urban issue. Table 3 lists the MIR for several compounds, including the 

hydrocarbons examined in this analysis. 

 

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

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

2016)

7 VM version VM_IO file_v4.4_10.13.14 and CMAQ model version 5.0.2 were used in this analysis.
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Table 3. Propensity of Refrigerants to Form Tropospheric Ozone

Compound North America MIR Scale 

(g-O3/g-substance) 

HCFC-22 <0.1 

HFC-134a <0.1 

Propylene 11.57 

Ethanea 0.28 

Isobutane 1.34 

Propane 0.56 

Source: IPCC (2005) 

a EPA uses the reactivity of ethane as the threshold for determining whether a compound has negligible 

reactivity. Compounds that are less reactive than, or equally reactive to, ethane under certain assumed 

conditions may be deemed negligibly reactive and therefore suitable for exemption from the definition of a 

VOC (EPA 2012a). 

As demonstrated in Table 3, the MIR for propylene, R-443A’s largest component (see Table 1), is more 

than 20 times greater than the MIR for propane, and approximately 9 times greater than the MIR for 

isobutane. Therefore, propylene is significantly more likely to form tropospheric ozone than other 

refrigerants examined in this analysis. 

These analyses estimated hydrocarbon refrigerant emissions in 2030 (EPA 2014) and 2040 (EPA 2016) 

from different scenarios and compared their resulting relative increases in ozone concentrations against the 

National Ambient Air Quality Standard (NAAQS) for ozone of 70 ppb.8 All three regions examined in 

these analyses (i.e., Los Angeles, Atlanta and Houston) are forecast to be in attainment of the 2015 8-hr 70 

ppb ozone standard by 2040. 

Isobutane, a less reactive hydrocarbon than propylene, was modeled in all refrigeration and air 

conditioning equipment. The results of this scenario indicate there could be an incremental increase up to 

0.72 ppb in 2030. In the alternative 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 6.6 ppb ozone in 2030 (EPA 2014) or 7.8 ppb ozone in 2040. 

Although potential impacts from isobutane were only modeled in 2030, the relative impact of isobutane in 

2040 is still anticipated to be significantly less than that of propylene, because isobutane is significantly 

less reactive. 

EPA performed an additional analysis to determine refrigerant emissions resulting from the use of 

propylene in a limited number of refrigeration and air conditioning end-uses including chillers, cold 

storage warehouses, and certain residential and light commercial air conditioning applications and their 

potential contributions to tropospheric ozone generation. Emissions from these select end-uses were 

estimated to result in an incremental maximum increase of the 8-hour average of up to 4.5 ppb in 2040. In 

addition, EPA examined a more realistic scenario in which refrigerant emissions from propylene and R443A were modeled in cold storage warehouses, residential and light commercial air conditioning, and 

large commercial air conditioning applications including chillers, as well as refrigerant emissions from R441A and propane in room air conditioners. Refrigerant emissions from this scenario resulted in an 

incremental maximum increase of the 8-hour average of 2.6 ppb in 2040. The increase in ozone is 

estimated to be about 95 percent associated with the use of propylene as a refrigerant, including its use as a 

component of R-443A, and 4 percent from propane, including its use as a component of R-443A and R441A, under this scenario. The results of the CMAQ modeling are summarized in Table 4. 

 

8 On October 1, 2015, EPA strengthened the NAAQS for ground-level ozone to 70 ppb from 75 ppb, based on scientific evidence 

about ozone’s effects on public health and welfare (EPA 2015).
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Table 4. Estimated Maximum Increase in the Daily 8-hour Ground-Level Ozone in 2040 from 

Hydrocarbon Refrigerant Emissions

Equipment Refrigerant 

8-hr Ozone 

Maximum Change 

(ppb) 

All refrigeration and air conditioning 

equipment 

Propylene 7.8 

Isobutane 0.72a

Chillers, cold storage warehouses, and 

certain residential and light commercial air 

conditioning applications 

Propylene 4.5 

Propane, Propylene, R441A, R-443A 2.6b

a The 8-hr maximum increase in ground-level ozone is observed in 2030 for the isobutane scenario. 

b 95 percent of the change in ozone is associated with the use of propylene as a refrigerant and as a 

component of R-443A, and 4 percent from propane as a refrigerant and as a component of R-441A and R443A, under this scenario. 

Although most ozone nonattainment areas are not VOC-limited (i.e., the formation of ozone in these areas 

is not by limited by VOC emissions, but by other compounds such as nitrogen oxides [NOx]), allowing the 

use of R-443A in residential and light commercial AC could introduce VOC loading that would place a 

further burden on reaching attainment and extend the timeline for compliance for some areas. 

Because propylene, R-443A’s largest component, is highly reactive, VOC emissions from the use of R443A in residential and light commercial AC units are anticipated to contribute to ground-level ozone 

concentrations in the United States significantly more than less reactive hydrocarbons and other available 

options for these end-uses, such as propane or HFC-32. Therefore, R-443A is not recommended for SNAP 

approval as a refrigerant in residential and light commercial AC and heat pumps. 

5. DISCUSSION OF END-USE SCENARIOS MODELED 

R-443A has been proposed for use in residential and light commercial AC units and heat pumps, including 

window AC units, split-systems,9

 residential heat pumps, and portable AC units. This risk screen evaluates 

refrigerant releases from all of the proposed room AC systems in a single room based on the smallest and 

largest proposed charge sizes. Charge sizes for the systems modeled in this risk screen are shown in Table 

5. 

Table 5. Charge Sizes for R-443A Residential Air-Conditioning Applications 

Application Minimum Modeled

Charge Size (g) 

Maximum Modeled 

Charge Sizeb (kg) 

Window Units 160a 245 

Ducted Split-Systems 416b 1,560 

a Acceptable charge size for R-443A window AC units installed in a 41 m3 room (ANSI/UL 2012). 

b Charge size indicated by the submitter (A.S. Trust & Holdings, 2015).

The 160-gram charge size for window units is consistent with UL Standard 484: Room Air Conditioners, 

which limits the charge size of single-room AC units for ASHRAE classified A3 refrigerants based on the 

lower flammability limit of the refrigerant and the volume of the room at end-use (ANSI/UL 2012). The

submitter indicates a charge size of 245 grams for window units. 

The ducted split-systems proposed by the submitter are not governed by UL 484, because they are 

intended to serve multiple rooms. Therefore, this risk screen models the submitter’s minimum charge size 

 

9

 Split-systems consist of an evaporator section installed indoors and a condensing unit installed outdoors, which are connected by 

refrigerant piping and electrical wiring (UL 2013). Such systems can be further classified as ducted, ductless mini-split, or ductless 

multi-split. 
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of 416 grams for ducted split-system AC units, consistent with the International Electrotechnical 

Commission (IEC) Standard 60335-2-40: Particular requirements for electrical heat pumps, air 

conditioners, and dehumidifiers.10 The submitter indicates a maximum charge size of 1,560 grams for 

ducted split-system AC units serving multiple rooms (A.S. Trust & Holdings 2015).11 Although the 

submitter did not propose using R-443A in split-systems covered under UL 484, the standard’s maximum 

allowable charge size of 290 grams for single-room split-systems containing R-443A is discussed in 

Sections 7 and 9 of this risk screen. 

Window and split-system AC units can be installed in a wide range of locations with varying room 

volumes. To represent a reasonable worst-case scenario for window and ducted split-system AC units, it is 

assumed that a catastrophic leak of refrigerant occurs in a bedroom where the AC unit is located. The 

analysis in this risk screen conservatively assumes that the AC unit is located in a bedroom with an 

effective volume of 41 m3 (1,450 ft3) (i.e., excluding the space filled by furniture, etc.) and a height of 2.4 

meters (7.8 feet). 

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

course of one minute into a bedroom with 0.11 air change(s) per hour (ACH) or 0.67 ACH.12 During the 

cooling season (May to September), ACH 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 both charge sizes (245 and 1,560 

grams). 

UL 484 assumes that window AC and split-system units are installed at a height of 1 meter and 1.8 meters 

above the ground, respectively. Although UL 484 is not applicable to ducted split-systems that serve 

multiple rooms, for this analysis, it is assumed that all split-system units and/or vents for ducted-split 

systems would be installed at similar heights.Based on this location and since R-443A is denser than air 

(specific gravity of R-443A relative to air is 1.49 [air=1]) and will settle in higher concentrations closer to 

the ground, a vertical concentration gradient is also assumed. In order to simulate the vertical 

concentration gradient of refrigerant following release, it is assumed that 95 percent of the leaked 

refrigerant mixes evenly into the lower meter (3.3 feet) or 1.8 meters (5.9 feet) of the room, and the rest of 

the refrigerant mixes evenly in the remaining volume (Kataoka 2000).13 Table 6 details the end-use 

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

 

10 IEC 60335-2-40 limits the charge size of room AC units, including split-systems, for flammable refrigerants based on the lower 

flammability limit of the refrigerant and the volume of the room at end-use (IEC 2013). 

11 The submitter also indicates a typical charge size of 340 grams for portable room AC units (A.S. Trust & Holdings 2013).

12 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 or wall 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 or wall AC units, while the remaining use central air 

conditioning equipment (EIA 2013). On average, 38 percent of homes built before 1990 use window or wall 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 or wall AC units, EPA does not 

expect that there is any significant mechanical ventilation present in the home. 

13 UL 484 assumes AC units installed near floor level, such as portable room AC units, are installed at a height of 0.6 meters above 

the ground (ANSI/UL 2012). 95 percent of the leaked refrigerant from portable room AC units is assumed to mix evenly in the 

bottom 0.6 meters of the room. The results of the flammability, asphyxiation, and end-use exposure assessments for portable AC 

units are not shown in this risk screen, because the results fall within the range of exposures for window units and ducted splitsystems in Sections 7, 8, and 9.
March 28, 2016 – Final 

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Table 6. End-Use Scenario Model Assumptions 

Parameter Assumptions

Room Type Bedroom

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

Ventilation Rate 

(air changes per hour) 0.11b

; 0.67c

Air Conditioning Unit Window AC Ducted Split-System AC

Charge Size (g) 160d, 245e 416e, 1,560e

Length of Release (minutes) 1 1

Vertical Concentration Gradient Yesf Yesg

a

 Background Document (EPA 1994) 

b Tight construction home (ACCA 2006) 

c

 Loose construction home (ACCA 2006) 

d Acceptable charge size for R-443A window AC units installed in a 41 m3 room (ANSI/UL 2012) 

e Charge size indicated by the submitter (A.S. Trust & Holdings 2015)

f The end-use scenario for window units assumes a vertical concentration gradient of 1 meter (3.3 feet) in accordance 

with UL 484 (ANSI/UL 2012). 

g

 The end-use scenario for split-systems assumes a vertical concentration gradient of 1.8 meters (5.9 feet) in 

accordance with UL 484 (ANSI/UL 2012). 

6. POTENTIAL HEALTH EFFECTS 

To assess potential health risks from exposure to the proposed substitute in residential and light 

commercial AC and heat pumps, EPA identified the relevant toxicity threshold values for comparison to 

modeled exposure concentrations for different scenarios. According to ASHRAE Standard 34, R-443A is 

listed under safety group A3 with a RCL of 1,700 ppm (ASHRAE 2013a). ASHRAE 34 RCLs are 

intended to reduce the risks of acute toxicity, asphyxiation, and flammability hazards in normally 

occupied, enclosed spaces during refrigerant use and protect end-users from the potential dangers of a

catastrophic leak from a refrigeration unit (ASHRAE 2013a). ASHRAE Standard 15 implements the 

aforementioned standard, requiring that “the concentration of refrigerant in an enclosed space following a 

complete discharge of a high-probability system shall not exceed the RCL” (ASHRAE 2013b). As such, 

this risk screen references the RCL for R-443A in addition to the lower flammability limit (LFL), hypoxia 

no observed adverse effect level (NOAEL) and exposure limits, as an additional, conservative limit to 

ensure that significant flammability, asphyxiation, and end-use exposure risks, respectively, do not occur. 

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

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

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

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

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

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

short-term, end-use exposures were evaluated. Table 7 lists the relevant toxicity limits and RCL of R-443A 

and is followed by Table 8, 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. 
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Table 7. Exposure Limits of R-443A Components 

An explanation of each exposure limit and exposure-limit related terminology is described in Table 8. 

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

b ASHRAE (2013a) 

c

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

d 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. 

e

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

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

g

 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.” 

Table 8. Explanation of Exposure Limit-Related Terminology a

R-443A 

Component 

8-hr WGL (Long-term 

Exposure) 

ppm 

30-min EGL (Short-term 

Exposure) 

ppm 

Refrigerant Concentration 

Limit (RCL) 

ppm 

Propylene 500 (ACGIH-TLV) 1,500 (30-min ACGIH Excursion 

Limit)a

1,000b

Propane 1,000c (OSHA PEL/NIOSH 

REL)

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

6,900e (30-min AEGL-1) 5,300b

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

Organization Definition

OSHA Occupational Safety and Health Administration

NIOSH National Institute for Occupational Safety and Health

ACGIH American Conference of Governmental Industrial Hygienists

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 threshold-limit value (TLV)–TWA, set by ACGIH. 

AEGLb,c Acute Exposure Guideline Level 1 AEGL-1 is the airborne concentration (expressed as ppm or 

mg/m3) of a substance above which it is predicted that the general 

population, including susceptible individuals, could experience 

notable discomfort, irritation, or certain asymptomatic nonsensory 

effects, 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 
March 28, 2016 – 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

 NIOSH (2015) 

According to the safety data sheet (SDS), exposure to R-443A may be hazardous if inhalation, skin 

contact, or eye contact with the proposed substitute occurs. The most likely pathway of exposure is 

through inhalation. R-443A can cause symptoms of asphyxiation when present in concentrations high 

enough to significantly lower oxygen concentrations below 19.5 percent by volume, such as headaches, 

ringing in ears, dizziness, drowsiness, nausea, vomiting, depression of all senses, and also 

unconsciousness. Under some circumstances of over-exposure (i.e., oxygen levels fall below 6 percent by 

volume), death may occur. In addition, at high concentrations, propane, a component of R-443A, can act as 

a narcotic and cause central nervous system depression, including dizziness, drowsiness, and headaches. 

If R-443A is inhaled, person(s) should be immediately removed from the contaminated space and exposed 

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

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

sought. Exposures of R-443A to the skin may cause frostbite. In the case of dermal exposure, the SDS for 

R-443A recommends that person(s) immediately wash the affected area with water and remove all 

contaminated clothing; if frostbite occurs, bathe (not rub) the affected area with lukewarm, not hot, water. 

If water is not available, cover the affected area with a clean, soft cloth, and seek medical attention 

immediately. Exposures of R-443A to the eyes could cause eye irritation. In case of ocular exposure, the 

SDS for R-443A 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-443A can be minimized by following the exposure 

guidelines and ventilation and personal protective equipment (PPE) recommendations outlined in the SDS

for R-443A and this risk screen.

population, including susceptible individuals, could experience lifethreatening health effects or death, set by EPA. 

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. 

Long-Term Exposure

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

RELd Recommended Exposure Limit This is an 8-hour TWA recommended by NIOSH.

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

40-hour workweek, to which it is believed that nearly all workers 

may be repeatedly exposed, day after day, for a working lifetime 

without adverse effect according to ACGIH. 
March 28, 2016 – Final 

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7. FLAMMABILITY ASSESSMENT 

ASHRAE Standard 34 classifies R-443A as an A3 refrigerant. R-443A is flammable when its 

concentration in air is in the range of 2.03 percent to 10.3 percent by volume (20,300 ppm to 103,000 

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

could occur if the concentration of R-443A were to exceed the LFL of 20,300 ppm. The remainder of this

section addresses flammability risks and summarizes the recommended measures to ensure safe handling 

and use of the refrigerant during manufacture and servicing. 

7.1 Flammability Risks at Equipment and Substitute Manufacture 

As indicated by the submitter, the manufacture of R-443A refrigerant (i.e., formulation mixing) and the 

charging of R-443A residential and light commercial AC units occur in a closed system. As a result, 

releases of R-443A during manufacturing operations in the presence of an ignition source are not 

anticipated. 

All R-443A storage and transport equipment should be installed with safety devices that minimize the 

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

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

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

storage and transportation requirements/guidelines. Similar equipment safety and procedural requirements 

should be developed for R-443A and other flammable refrigerants. It is expected that refrigerants be 

properly stored and caution used within manufacturing facilities to minimize explosion risk and that 

workers adhere to the requirements set by OSHA under 29 CFR 1910. OSHA requirements include proper 

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

manufacturing practices should be adhered to during the manufacture of equipment containing R-443A, 

e.g., using proper ventilation. 

7.2 Flammability Risk at Servicing and End-Use 

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

5) was investigated for R-443A. Both servicing and end-use of R-443A window and ducted split-system 

AC units are expected to take place in the same space (i.e., the installation and use location). 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-443A immediately following the release of refrigerant were 

compared with the LFL for R-443A (i.e., 20,300 ppm). The results of the flammability assessment are 

presented in Table 9. 

Table 9. Flammability Assessmenta

Equipment Scenario Charge 

Size (g) 

Effective Room 

Size (m3) 

Vertical 

Concentration 

Gradient 

Maximum 

Instantaneous 

Concentration 

 (ppm) b,c

Window Units Reasonable Worst-Case Scenario 1a 160 41 (1,450 ft3) Yes 4,910 

Reasonable Worst-Case Scenario 1b 245 7,520 

Ducted SplitSystems 

Reasonable Worst-Case Scenario 2a 416 

41 (1,450 ft3) 

Yes 5,410 

Reasonable Worst-Case Scenario 2b 1,560 Yes 26,600 

Reasonable Worst-Case Scenario 2c No 20,000 

Window Units Threshold Analysis 1a: Charge Size 660 41 (1,450 ft3

) Yes 20,300 

Threshold Analysis 1b: Room Size 245 15 (540 ft3) Yes 20,300 

Ducted SplitSystems 

Threshold Analysis 2a: Charge Size 1,190 41 (1,450 ft3) Yes 20,300 

Threshold Analysis 2b: Room Size 1,560 54 (1,900 ft3) Yes 20,300 
March 28, 2016 – Final 

11 

Bold font indicates modeling results. 

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

b

 LFL of R-443A is 20,300 ppm. 

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

percent of the leaked refrigerant is present in this space. 

As presented in Table 9, the maximum instantaneous concentration in the lower compartment of the room 

does not exceed the LFL for R-443A (i.e., 20,300 ppm) for window units and Reasonable Worst-Case 

Scenarios 2a and 2c for ducted split-system AC units. However, the maximum instantaneous concentration

in the lower 1.8 meters of the room exceeds the LFL for R-443A (i.e., 20,300 ppm) in Reasonable WorstCase Scenario 2b, where a vertical concentration gradient is considered. Because the ducted split-system 

AC unit is expected to be installed at or near ceiling height (approximately 2 meters or 7 feet), it is 

reasonable to assume the refrigerant would mix evenly with air before settling to the ground. Therefore, 

Reasonable Worst-Case Scenario 2c was modeled without a vertical concentration gradient. 

Although Reasonable Worst-Case Scenario 2b exceeds the LFL for R-443A, it is also unlikely that the 

entire charge of the R-443A system will be released. The submitter indicates the condenser, compressor, 

refrigerant lines and other components of the ducted split-system are located outside, and such 

configurations employ a safety valve that limit the amount of R-443A that could be released indoors (A.S. 

Trust & Holdings 2013). As a result, releases of ducted split-system AC units with a 1,560 gram charge

size do not present a significant flammability risk in the reasonable worst-case scenario for R-443A. 

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

concentration in the lower meter of the room equals the LFL for R-443A) were also determined. 

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

R-443A window AC unit in a 41 m3 (1,450 ft3) room is 660 grams or more, which is larger than 

the maximum charge size allowed by UL 484 in a 41 m3

 room (i.e., 160 grams of R-443A for 

window units and 290 grams of R-443A for split-systems serving a single room). 

• Using the submitter’s charge size of 1,560 grams for R-443A ducted split-system AC units, as 

shown under Threshold Analysis 2b, the volume of the room would have to be approximately 54 

m3 (1,900 ft3

), or slightly larger than the modeled room size for flammability to be of concern. 

According to the results of this flammability analysis, the risk of fire is minimal if a window or splitsystem AC unit is installed in a room with volumes in accordance with standards and regulations and if it 

meets the requirements of UL 484 for equipment serving a single room. As bedrooms can be smaller than 

those modeled in this assessment14 and because persons or equipment in the room may reduce the effective 

volume of the space, AC units containing R-443A should not be installed in enclosed areas with effective 

volumes less than indicated by relevant safety standards (e.g., ASHRAE 15, 34, and UL 484) unless 

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

8. ASPHYXIATION ASSESSMENT 

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

for R-443A. In this section, risk of asphyxiation is assessed in three ways: 

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

 

14 International Residential Code requires a minimum of 6.5 m2

 (70 ft2) for a habitable room, or 14 m3 (490 ft3) (ICC 2015). 
March 28, 2016 – Final 

12 

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

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

expected to cause an asphyxiation risk), and 

3) Performing a threshold analysis of the maximum room size at which an asphyxiation risk could 

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

are expected to cause an asphyxiation risk). 

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

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

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

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

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

assumptions in place, it can be reasonably assumed that no risks of asphyxiation will be present under realworld conditions. The results of the asphyxiation assessment are summarized in Table 10 below. 

Table 10. Asphyxiation Assessmenta,b 

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

Percent Oxygen 

Concentration in 

Lower Meter 

Reasonable Worst-Case Scenario 1 245 41 (1,450 ft3

) 21% 

Reasonable Worst-Case Scenario 2 1,560 20% 

Threshold Analysis 1: Charge Size 12,800 41 (1,450 ft3) 12% 

Threshold Analysis 2: Room Size 1,560 5 (180 ft3) 12% 

Bold font indicates modeling results. 

a

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

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

b

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

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

reduced to 12 percent.15 Based on the reasonable worst-case scenario modeling, a release of R-443A from 

window or ducted split-system AC units has an insignificant impact on the concentration of oxygen in the 

air and therefore does not present a significant risk of asphyxiation. This modeling does not take into 

account any ventilation which is likely to occur, 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 person(s) is likely to be even smaller than modeled. 

For the asphyxiation threshold analyses shown in Table 10, the conditions at which an asphyxiation 

concern would exist were determined. 

• As shown under Threshold Analysis 1, the charge size of the window or ducted split-system AC 

unit in a 41 m3

 (1,450 ft3) room would have to be at least 12,800 grams for asphyxiation to be a 

concern, which is approximately 8 times greater than the maximum modeled charge size (i.e., 

1,560 grams). 

• Using the charge size of 1,560 grams for ducted split-system AC units, as shown under Threshold 

Analysis 2, the volume of the room would have to be approximately 5 m3 (180 ft3

), or 

approximately 8 times smaller than the modeled room size for asphyxiation to be of concern. 

Based on the worst-case modeling results and threshold analysis, EPA does not believe that the use of R443A in window or split-system AC units poses a significant risk of asphyxiation or impaired coordination 

 

15 Twelve percent oxygen in air is the NOAEL for hypoxia (ICF 1997). 
March 28, 2016 – Final 

13 

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

manufacturer and the SDS for R-443A. 

9. END-USE EXPOSURE ASSESSMENT 

This section presents estimates of potential end-user exposures to R-443A in the event of a catastrophic 

release from the proposed substitute’s use in window and ducted split-system AC units. An end-use 

exposure analysis was performed to examine potential catastrophic releases of R-443A under the 

reasonable worst-case scenario outlined in Section 5. 

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

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

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

from catastrophic leakage of refrigerant from a ducted split-system AC unit were examined. As discussed 

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

was undertaken to determine the 30-minute TWA exposures of R-443A components, which were then 

compared to the standard toxicity limits presented in Table 7 to assess the risk to end-users. The estimated 

TWA values are fairly conservative as the analysis reflects minimal airflow (i.e., natural ventilation), but 

does not consider mechanical ventilation such as fans, conditioned airflow (either heated or cooled) and 

other variables that would reduce the levels to which individuals would be exposed. Because propylene is 

present in larger concentrations and because it has a lower exposure limit than other R-443A components, 

Table 11 only displays exposures for propylene, the component with greater potential concerns. Modeling 

results are presented in Table 11. 

Table 11. End-Use Exposure Assessment of R-443A Propylene Componenta 

Equipment Scenario Charge 

Size (g)b

Effective Room 

Size (m3) 

Air 

Exchange 

Rate (ACH) 

Vertical 

Concentration 

Gradient 

30-minute 

TWA EndUse 

Exposure 

(ppm)c, d

Window Units 

Reasonable Worst-Case Scenario 1a 160 41 (1,450 ft3

) 

0.67

Yes 2,380 

Reasonable Worst-Case Scenario 1b 245 3,650 

Reasonable Worst-Case Scenario 1c 160 41 (1,450 ft3

) No 990 

Reasonable Worst-Case Scenario 1d 245 1,520 

Ducted SplitSystems 

Reasonable Worst-Case Scenario 2a 416 41 (1,450 ft3

) 

0.67 

Yes 3,440 

Reasonable Worst-Case Scenario 2b 1,560 12,900 

Reasonable Worst-Case Scenario 2c 416 41 (1,450 ft3

) No 2,580 

Reasonable Worst-Case Scenario 2d 1,560 9,680 

Window Units 

Threshold Analysis 1a: Charge Size 100 41 (1,450 ft3) 0.67 Yes 

1,500 

Threshold Analysis 1b: Room Size 245 110 (4,020 ft3) 0.11

Threshold Analysis 1c: ACH 245 41 (1,450 ft3) 5 Yes

Ducted SplitSystems 

Threshold Analysis 2a: Charge Size 180 41 (1,450 ft3) 0.67 Yes Threshold Analysis 2b: Room Size 1,560 400 (14,200 ft3

) 0.11

Threshold Analysis 2c: ACH 1,560 41 (1,450 ft3) 20 Yes

Bold font indicates modeling results. 

a

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

b An R-443A unit with a charge size of 160 grams contains 88 grams of propylene; 245 grams of R-443A contains 135 grams of propylene; 416 

grams of R-443A contains 229 grams of propylene; and 1,560 grams of R-443A contains 858 grams of propylene. 

c

 EPA-derived STEL (see Table 7) 

d

 Values provided in this column refer to the concentration in the lower 1 meter of the room for window units and 1.8 meters for split-systems, 

which presents the most conservative risk as 95 percent of the leaked refrigerant is present in this space. 
March 28, 2016 – Final 

14 

Under the reasonable worst-case scenario described in Section 5 for window and ducted split-system AC 

units, the anticipated 30-minute TWA exposures of R-443A following catastrophic releases of window and

ducted split-system AC units were modeled with two air exchange rates, 0.11 ACH and 0.67 ACH. 

According to the results in Table 11, the 30-minute STEL for propylene (i.e., 1,500) is likely to be 

exceeded in all reasonable worst-case scenarios, excluding Reasonable Worst-Case Scenario 1c. 

Reasonable Worst-Case Scenario 1c models the smallest proposed charge size of 160 grams in the least 

conservative end-use scenario (i.e., highest ventilation rate of 0.67 and no vertical concentration gradient). 

Because modeled exposures exceed the STEL for propylene, the largest constituent of R-443A and the 

component with greater toxicity concern, it is also likely that the RCL for R-443A would be exceeded at 

end-use. 

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

determine the charge size, room size and ventilation requirements that ensure that the use of R-443A in 

this end-use does not present risk to end-users or servicing technicians. Based on these results, a room 

volume of 41 m3 (1,450 ft3) should not contain an AC unit with a charge size that exceeds 100 grams, 

assuming an ACH of 0.67 (Threshold Analysis 1a in Table 11). The analysis also indicates a split-system 

AC unit with a charge size of 1,560 grams should not be installed in a room of effective volume less than 

400 m3

 (14,200 ft3), assuming an ACH of 0.67 (Threshold Analysis 2b in Table 11). In addition, although 

the submitter indicates a complete loss of refrigerant is unlikely due to the presence of a safety valve, a 

release of 40 percent of the 245-gram refrigerant charge for window units, 60 percent of the 290-gram 

refrigerant charge for split-systems covered by UL, and only 11 percent of the 1,560-gram refrigerant 

charge for ducted split-systems could lead to an exposure concern (see Threshold Analyses 1a and 2a). 

In order for toxicity risk to not be of concern, the results of the threshold analyses indicate R-443A would 

have to be installed under room size and ventilation conditions that are not typical of residential rooms (see 

Table 11). For instance, the recommended air exchange rate for R-443A in the modeled room size is 

approximately 45 times greater than the typical air exchange rate for residential rooms (i.e., 0.45 ACH) 

(EPA 1997). Because R-443A presents a significant toxicity risk at end-use for both the submitter’s typical 

charge sizes and the charge sizes recommended by UL 484 (i.e., 160 and 290 grams), R-443A is not 

recommended for SNAP approval in residential and light commercial AC and heat pumps, specifically 

window AC units, split-system AC units, residential heat pumps, and portable AC units. 

10. OCCUPATIONAL EXPOSURE ASSESSMENT 

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

disposal of R-443A window and split-system AC units. To determine whether the use of the proposed 

substitute in window and ducted split-system AC units poses an unacceptable toxicity risk to workers 

during servicing and disposal, occupational exposure modeling was performed using a box-model 

approach. For a detailed description of the methodology used for this screening assessment, the reader is 

referred to the occupational exposure and hazard analysis described in Chapter 5 of the Background 

Document. 

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

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

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

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

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

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

(representing a catastrophic release). It was assumed that 10 units are disposed of during an 8-hour work 

day; however, it was assumed that of the 10 units, only the last unit per workday would experience the

catastrophic release (i.e., 100 percent). The remaining 9 units were assumed to release an incidental 
March 28, 2016 – Final 

15 

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

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

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

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

substitute (see Section 10.3). 

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

charging and servicing and long-term exposure limits at disposal. Similar to the end-use exposure 

assessment, Tables 12 and 13 only present exposures for propylene, the component with the greater 

potential concern. 

10.1 Occupational Exposure at Manufacture of Substitute 

R-443A is produced in the United States. During manufacture of R-443A, the SDS should be referenced 

and proper engineering controls and PPE used. 

The submitter indicates R-443A is manufactured in closed systems constructed for safety and elimination 

of environmental releases and worker exposure (A.S. Trust & Holdings 2013). Therefore, R-443A is not 

expected to pose a risk to workers during manufacture or blending when the engineering controls and PPE 

recommendations referenced in the SDS for R-443A are followed. Release points/exposure in chemical 

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

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

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

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

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

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

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

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

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

hygiene and manufacturing practices and the SDS for R-443A, there is no significant risk to workers 

during the manufacture of R-443A.

10.2 Occupational Exposure at Charging and Servicing 

Window and ducted split-system AC units would typically be charged by the Original Equipment 

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

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

lines for charging and recovery equipment. 

Window and ducted split-system AC units are expected to be serviced rarely, since this type of equipment 

is hermetically sealed. Generally, in the United States, these units are replaced rather than serviced if the 

charge leaks. Nevertheless, the potential occupational exposure during servicing was analyzed. The 

possibility of a release during installation was also considered. The maximum 30-minute TWA exposure 

for each component in R-443A was estimated for servicing window and ducted split-system AC units 

charged with 245 grams or 1,560 grams of R-443A. 

Installation and servicing activities for R-443A window and ducted split-system AC units are not expected 

to result in significant worker exposure when certified technicians follow the procedures outlined in the R443A SDS and maintenance manual, undergo proper training, and wear appropriate PPE (e.g., gloves and 

safety glasses). Nevertheless, the potential occupational exposure during servicing was analyzed. The 

maximum 30-minute TWA exposures for propylene, the R-443A constituent with greater potential 

concern, were estimated and compared to the STEL (see Table 12). The modeling results indicate that the 

maximum anticipated occupational exposure concentrations do not exceed the STEL for propylene (i.e., 

1,500 ppm). 
March 28, 2016 – Final 

16 

Table 12. Occupational Risk Assessment at Servicinga

R-443A 

Component 

30-minute TWA 

Occupational Exposure 

(ppm) 

30-minute TWA 

Occupational Exposure 

(ppm) 

30-min Short 

Term Exposure 

Limits (ppm) 

Charge Size: 245 grams Charge Size: 1,560 grams

Propylene 1 7 1,500b 

Bold font indicates modeling results. 

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

options. 

b

 EPA-derived STEL (see Table 7) 

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

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

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

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

window and split-system AC units containing R-443A presents a significant concern to workers. 

10.3 Occupational Exposure at Disposal 

Disposal of R-443A window and split-system AC units is expected to occur with limited frequency (up to

approximately ten disposal events per day) at disposal facilities and with limited duration of exposure to 

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

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

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

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

recovery equipment would be used (see Section 10.2 and Table 12 for information and modeling results 

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

within 15-30 minutes (per event/day). 

Table 13 displays the maximum estimated 8-hour TWA occupational exposure levels for R-443A 

component, propylene, during disposal. To model a worst-case scenario, it was assumed that of the 10 

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

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

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

exposure limits for R-443A’s component with the greatest potential concern, occupational exposure to the 

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

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

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

proper industrial hygiene techniques while wearing PPE. 

Table 13. Occupational Risk Assessment at Disposala

R-443A 

Component 

8-Hour TWA Occupational 

Exposure (ppm) 

8-Hour TWA Occupational 

Exposure (ppm) 

8-Hour Long Term 

Exposure Limits 

(ppm) Charge Size: 245 grams Charge Size: 1,560 grams 

Propylene 54 310 500b 

Bold font indicates modeling results. 

a

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

options. 

b

 OSHA PEL 

c ACGIH TLV 
March 28, 2016 – Final 

17 

11. GENERAL POPULATION EXPOSURE ASSESSMENT 

This section presents an assessment of potential risks to the general population posed by the use of R-443A 

in residential and light commercial AC and heat pumps. The general population is defined in this risk 

screen as non-personnel who are subject to exposure of the proposed substitute near industrial facilities, 

including manufacturing or equipment production factories, equipment operating sites (for on-site 

installation or disposal activities only), or recycling centers, rather than consumers at end-use. 

R-443A is not expected to cause a significant risk to human health in the general population when 

manufactured for use and used as a refrigerant in residential and light commercial AC and heat pumps. The 

proposed substitute will be manufactured in a closed process and is proposed for use in closed systems; 

thus, significant releases are not anticipated. At room temperature, R-443A is a gas; therefore, releases to 

ground or surface water are not anticipated, as R-443A is anticipated to dissipate into the atmosphere upon 

release to outside air (i.e., because natural ventilation rates would be higher and there is no enclosed space 

to maintain a high concentration of R-443A). Should air releases during manufacturing operations occur, 

engineering controls should be used (e.g., carbon absorption scrubbers) to collect R-443A and prevent the 

release of the chemical to the atmosphere. EPA believes that by using proper engineering controls and by 

following disposal and containment recommendations outlined in the proposed substitute’s SDS and this 

risk screen, exposure to R-443A is not expected to pose a significant toxicity risk to the general 

population.
March 28, 2016 – Final 

18 

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International Electrotechnical Commission (IEC). 2013. IEC 60335-2-40: Household and similar 

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

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