SNAP TECHNICAL BACKGROUND DOCUMENT:

RISK SCREEN ON THE USE OF 

SUBSTITUTES FOR CLASS I

OZONE-DEPLETING SUBSTANCES:

REFRIGERATION AND AIR CONDITIONING

U.S. Environmental Protection Agency

Office of Air and Radiation

Stratospheric Protection Division

Mail Code 6205J

401 M Street, S.W.

Washington, D.C. 20460

March 1994
ii

NOTICE

This background document supports the U.S. Environmental Protection Agency's (EPA) 

rulemaking for controlling the replacement of Class I ozone-depleting substances (ODSs) with any 

substitute that presents unacceptable risk to human health or the environment where safer 

alternatives are available. Specifically, this document examines the risk from the use of various 

refrigeration and air conditioning substitutes. Similar documents address other industry sectors.

ICF Incorporated provided support for the preparation of this document at the technical 

direction of the Stratospheric Protection Division, Office of Air and Radiation, EPA, Contract No. 

68-D9-0068, Work Assignments 3-23 and 3-69; and Contract No. 68-C2-0107, Work 

Assignment 39; and Contract No. 68-D3-0021, Work Assignments 1-11 and 2-18. Meridian 

Research Incorporated also provided technical support under Contract No. 68-D9-0068, Work

Assignment 3-68 and Contract No. 68-D3-0021 Work Assignment 2-18, particularly for the 

occupational evaluation. ZBA, under Work Assignment 3-74, provided technical support for 

evaluating the feasibility of substitutes.
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TABLE OF CONTENTS

Section Page

Notice ............................................................................................................................................. ii

Executive Summary....................................................................................................................... vi

ES.1 The Refrigeration and Air Conditioning Sectors................................................... vi

ES.2 Risk Screening Methodology............................................................................... viii

ES.3 Risk Screening Results ............................................................................................x

1. INTRODUCTION ........................................................................................................... 1-1

1.1 Background.......................................................................................................... 1-1

1.2 Evaluation of Substitutes..................................................................................... 1-2

1.3 Risk Screening Reports for Refrigeration and 

Air Conditioning .................................................................................................. 1-3

2. OVERVIEW OF SUBSTITUTES AND END USES ..................................................... 2-1

2.1 End Uses .............................................................................................................. 2-1

2.2 Alternative Refrigerants....................................................................................... 2-2

2.2.1 HCFCs...................................................................................................... 2-2

2.2.2 HFCs........................................................................................................ 2-3

2.2.3 Hydrocarbons........................................................................................... 2-3

2.2.4 Ammonia.................................................................................................. 2-3

2.2.5 Chlorine.................................................................................................... 2-3

2.2.6 Potential Substitutes Manufacturers Have Submitted as

Confidential Business Information .......................................................... 2-4

2.3 Alternative Technologies..................................................................................... 2-4

2.3.1 Absorption Refrigeration Systems........................................................... 2-4

2.3.2 Evaporative Cooling ................................................................................ 2-4

3. TOXICITY REFERENCE VALUES FOR SUBSTITUTES.......................................... 3-1

3.1 Occupational (Inhalation) Exposure Limits......................................................... 3-1

3.2 General Population/Consumer (Inhalation) Toxicity Reference Values............. 3-6

3.2.1 Reference Concentrations (RfCs) ............................................................ 3-6

3.2.2 Cancer Slope Factors .............................................................................. 3-8

Chapter 3 References....................................................................................................... 3-9

4. ATMOSPHERICS MODELING..................................................................................... 4-1

4.1 Introduction.......................................................................................................... 4-1

4.2 Description of Refrigerator and Air Conditioning End Uses............................... 4-1

4.3 Control Options.................................................................................................... 4-4

4.4 The Baseline for the Analysis.............................................................................. 4-4

4.4.1 Uniform Assumptions Made Throughout the Analysis........................... 4-4

4.4.2 Assumptions Made for All Other End Uses ............................................ 4-5

4.4.3 Assumptions Made Within the End Use of Concern............................... 4-5

4.4.3.1 Ideal Substitute Baseline............................................................ 4-5

4.4.3.2 No Substitution Baseline ........................................................... 4-7
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4.5 Overview of the Modeling Approach .................................................................. 4-8

4.5.1 Chemical Use ........................................................................................... 4-8

4.5.2 Chemical Emissions................................................................................. 4-8

4.5.3 Atmospheric Effects................................................................................. 4-8

4.5.4 Human Health Effects.............................................................................. 4-9

4.6 Model Results.................................................................................................... 4-10

4.6.1 Description of the Results...................................................................... 4-10

4.6.2 Interpreting the Results.......................................................................... 4-10

4.7 Global Warming ............................................................................................... 4-92

4.7.1 The Nature of the Global Warming Problem......................................... 4-93

4.7.2 Properties of Greenhouse Gases ............................................................ 4-93

4.7.3 Properties of CFCs and CFC Substitutes............................................... 4-95

4.7.4 Indirect Effects from Changes in Energy Efficiency............................. 4-98

4.7.4.1 Refrigeration and Air Conditioning End Uses........................... 4-98

4.7.4.2 Foam Insulation ......................................................................... 4-99

Chapter 4 References................................................................................................... 4-100

5. OCCUPATIONAL EXPOSURE AND HAZARD ANALYSIS..................................... 5-1

5.1 Introduction.......................................................................................................... 5-1

5.2 Description of the Model ..................................................................................... 5-1

5.3 Discussion of the Results..................................................................................... 5-4

5.3.1 Presentation of Results............................................................................. 5-4

5.3.2 Interpretation and Comparison of Model Results with Sampling Data... 5-5

5.4 Potential Workplace Flammability and Explosivity Risks.................................. 5-8

Chapter 5 References ................................................................................................... 5-10

6. CONSUMER EXPOSURE AND RISK SCREENING ANALYSIS.............................. 6-1

6.1 Home Appliances................................................................................................. 6-2

6.1.1 Risks from Long-term Exposure to Leakage and Servicing Events C

Previous Estimates................................................................................... 6-2

6.1.2 Risks form Short-term Exposure During Servicing and Accidental

Releases.................................................................................................... 6-3

6.1.3 Summary of Modeling Results.............................................................. 6-10

6.1.4 Safety Concerns: HFC-152a in Household Refrigerators ................... 6-10

6.2 Mobile Air Conditioners (MACs)...................................................................... 6-11

6.2.1 Approach Used in a Previous Consumer Exposure Report ................... 6-11

6.2.2 Comparison of Parameters Contained in Consumer Exposure Report 

with Data from Other Sources ............................................................... 6-12

6.2.3 Summary................................................................................................ 6-13

Chapter 6 References..................................................................................................... 6-14

7. GENERAL POPULATION EXPOSURE AND RISK ANALYSIS .............................. 7-1

7.1 HCFCs and HFCs ................................................................................................ 7-1

7.1.1 Approach.................................................................................................. 7-1

7.1.2 Results...................................................................................................... 7-4

7.1.3 Caveats and Limitations........................................................................... 7-4

7.1.4 Conclusions.............................................................................................. 7-7

7.2 Other Alternative Refrigerants............................................................................. 7-7

7.2.1 Background.............................................................................................. 7-8
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7.2.2 Approach.................................................................................................. 7-8

7.2.3 Results .................................................................................................... 7-9

7.3 Chlorine................................................................................................................ 7-9

7.4 Lithium Bromide and Ammonia in Absorption Systems .................................. 7-11

Chapter 7 References..................................................................................................... 7-12

Attachment 7-A: Detailed Categorization of Refrigeration End Uses and 

 Equipment Types...........................................................................7-A-1

Attachment 7-B: Assumptions for Ambient Air Release Calculations..................... 7-B-1

Attachment 7-C: Methodology for Estimating General Population Exposures to Ambient 

 Air Releases of Substitutes for Class I Substances for SNAP Risk 

Screens 7-C-1

Attachment 7-D: Detailed Results.............................................................................7-D-1

Attachment 7-E: Percent of Equipment with Assumed Charge Size ........................ 7-E-1

8. VOLATILE ORGANIC COMPOUND ANALYSIS...................................................... 8-1

8.1 VOC Emissions from Substitutes to Class I ODSs.............................................. 8-1

8.2 VOC Emissions from All Sources....................................................................... 8-1

8.3 Comparison of VOCs from Substitutes to VOCs from All Sources.................... 8-1

8.4 Caveats and Limitations....................................................................................... 8-2

Chapter 8 References....................................................................................................... 8-3

Attachment 8-A: Estimation of Total VOC Emissions from All Sources in 1995....8-A-1

Attachment 8-B: VOC Controls................................................................................ 8-B-1
EXECUTIVE SUMMARY

This report presents a screening assessment of human health and environmental risks 

associated with the use of potential substitutes for ozone depleting substances (ODSs) in the 

refrigeration and air conditioning sectors.1 ODSs are being phased out of production in response 

to a series of diplomatic and legislative efforts that have taken place in the past few years, 

including the Montreal Protocol and, more recently, the Clean Air Act Amendments of 1990. The 

analyses presented in this report support the United States Environmental Protection Agency's 

Significant New Alternatives Policy (SNAP) Program, which is authorized by Section 612 of the 

Clean Air Act Amendments. Implementation of this program involves: (1) developing, 

promulgating, and administering a regulatory program for identifying and evaluating substitutes, 

and (2) publishing a list of acceptable and unacceptable substitutes for specific end uses.

The remainder of this summary provides an overview of ODS use in the refrigeration and 

air conditioning sectors, the methodology used to conduct the risk screen, and the key results.

ES.1 THE REFRIGERATION AND AIR CONDITIONING SECTORS

ODS use in the refrigeration and air conditioning sectors accounted for almost 22 percent 

of the total use of Class I substances in the United States in 1990. CFC-12 is the most widely used 

refrigerant, with applications in mobile air conditioners (MACS), household refrigerators and 

freezers, various appliances, chillers, retail food refrigeration equipment, cold storage warehouses, 

refrigerated transport systems, and industrial equipment. CFC-11 is most commonly used to 

provide cooling for large buildings, while CFC-115, as a component in the refrigerant blend 

R-502, is used for low temperature applications in a variety of sectors. CFC-113 and CFC-114 

are used in special applications chillers.

Of the Class II controlled substances, HCFC-22 is the refrigerant of choice in small to 

medium size air conditioning systems, and some types of retail food and industrial process 

refrigeration systems.

EPA has divided the refrigeration and air conditioning sector into the following general 

end uses:

 Retail Food Systems: These include stand alone refrigeration cases found in small 

markets, convenience stores, restaurants and other food establishments, large 

systems found in supermarkets, commonly referred to as parallel systems, and 

HCFC-22 systems found in a wide variety of retail and service establishments;

 Cold Storage Systems: Public and private facilities used to store meat, produce, 

dairy products, frozen foods, and other perishable goods. These systems 

refrigerate warehouses of varying sizes and include high pressure and low pressure 

systems;

 

 

1

 Other ODS sectors evaluated in separate reports are solvent cleaning; foam blowing; fire 

extinguishing; aerosols; sterilants; and adhesives, coatings, and inks.
 Chillers: These are large commercial air conditioning systems used to cool office 

buildings, shopping malls, and other large indoor spaces. End uses include 

CFC-11 (low pressure) chillers, CFC-12 centrifugal chillers, CFC-12 reciprocating 

chillers, HCFC-22 chillers, CFC-114 centrifugal chillers, and CFC-500 centrifugal 

chillers;

 Industrial Process Refrigeration: Refrigeration systems used in the chemical, 

pharmaceutical, petrochemical, and other manufacturing and food processing 

industries. These include both packaged and built-up systems used in 

manufacturing processes as well as extra-large ice makers;

 Ice Skating Rinks: There are several different types of ice rink systems, but all are 

grouped into one end use in this analysis;

 Ice Makers: These include small, medium, and large ice makers used by a number 

of entities, including restaurants and hotels;

 Household and Light Commercial Air Conditioning: These include window units, 

packaged terminal air conditioners, central air conditioners, direct expansion 

commercial air conditioners, and heat pumps used for space cooling and heating in 

homes and businesses. All systems in this end use currently use HCFC-22;

 Refrigerated Appliances: These include household refrigerators and freezers, 

water coolers, vending machines, and dehumidifiers. Most currently use CFC-12 

as a refrigerant, but there are some CFC-502 units in existence;

 Refrigerated Transport Systems: These include systems designed to refrigerate 

materials in transit. They are found in trucks, trains, and ships; and

 Mobile Air Conditioning: This end use includes systems installed in motor 

vehicles for the comfort of occupants.

The following substitutes to Class I and Class II substances are examined in this report: 

$ HCFCs: HCFCs are chemically similar to CFCs except that they contain 

hydrogen in addition to chlorine and fluorine. HCFCs analyzed as possible 

substitutes to the use of Class I chemicals in the refrigeration sector include 

HCFC-22, HCFC-123, HCFC-124, HCFC-141b, and HCFC-142b.

$ HFCs: HFCs do not contain chlorine and do not contribute to destruction of 

stratospheric ozone. They can, however, have high greenhouse gas potentials and 

may contribute to global warming. HFCs analyzed as possible substitutes to Class 

I and Class II substances in the refrigeration sector include HFC-134a, HFC-152a, 

HFC-143a, HFC-125, HFC-227ea, and HFC-23.

$ Hydrocarbons: Propane, ethane, propylene, and (to some extent) butane are used 

as refrigerants in specialized industrial applications, primarily in oil refineries and 

chemical plants. Perfluoropropane and other perfluorocarbons (PFCs) also have 

potential applications in the refrigeration sector.
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$ Ammonia: Ammonia has been used as a refrigerant in vapor compression cycles 

for more than 100 years. Its main application is in moderate to low temperatures 

systems.

$ Chlorine: Chlorine has been proposed as a Class I substitute refrigerant for use in 

chlorine liquification, a processing step in the manufacture of the chemical.

$ Potential Substitutes Submitted as Confidential Business Information. A few 

substitutes included in this analysis were submitted by their manufacturers as 

confidential business information. As a result the identity of these substances are 

not revealed. The results of the use analyses for these compounds are presented 

under the following identities: R200b through 200i; and 

HCFC/HFC/Fluoroalkane.

In addition to these chemical substitutes, there are a number of alternative technologies 

considered in this risk screening analysis:

$ Absorption Refrigeration Systems: Absorption refrigeration systems are a 

major existing alternative to systems based on vapor compression cycles. 

Ammonia and lithium bromide are used in absorption refrigeration and air 

conditioning systems.

$ Evaporative Cooling: Evaporative cooling is another technology that could be 

an alternative to CFC- and HCFC-based vapor compression systems in some 

applications. Contrary to vapor compression systems, evaporative coolers do not 

require compressors and consequently can offer considerable energy savings.

ES.2 RISK SCREENING METHODOLOGY

To examine risks associated with the use of substitutes for ODSs in each sector, EPA 

examined many different types of exposure routes, receptors, and effects. As discussed in more 

detail later, EPA used an atmospherics modeling framework to assess global ozone depletion and 

associated health effects. To examine risks to workers, consumers, and the general population, 

EPA first conducted screening-level assessments using generally conservative assumptions to 

identify scenarios potentially of concern, and then conducted more in-depth assessments of those 

scenarios. These risk screening assessments were conducted in three basic steps:

(1) Assess exposure. EPA estimated levels of substitutes to which workers, 

consumers, the general population, and environmental receptors may be exposed, 

and over what period of time.

(2) Evaluate toxicity. EPA compiled information on the toxicity of each substitute, 

including occupational exposure limits, reference concentrations, and cancer slope 

factors. These values were identified from an appropriate source (e.g., 

Permissible Exposure Limits [PELs] from the Occupational Safety and Health 

Administration [OSHA]) or were derived for this report using extrapolation and 

other techniques.

(3) Estimate risk. Exposure assessment results were combined with toxicity values to 

estimate risks. Uncertainties in the risk estimates were analyzed qualitatively.
ix

EPA did not estimate risks for every possible combination of substitute, end use, and type 

of effect; combinations that clearly were not of concern were not analyzed. For example, 

substitutes that volatilize quickly when exposed to the atmosphere were not examined for potential 

releases to streams and effects on aquatic life. EPA believes that all of the significant human 

health and environmental exposure pathways and effects were covered in the risk screen.

Below are brief descriptions of how the general approach discussed above was applied to 

the risk screen for the refrigeration sector.

Worker Exposure and Risk. EPA used a mass-balance model to estimate worker 

exposure to HCFC and HFC refrigerant and air conditioning substitutes for ODSs used in this 

sector. Potential exposure levels to the substitutes were assessed during the manufacture, 

installation, and servicing of refrigeration and air conditioning equipment. Estimated exposures 

were compared to OSHA and EPA occupational exposure limits to screen the potential risks to 

workers.

Consumer Exposure. Consumers may be exposed to ODS substitutes that could 

potentially be used in household refrigeration and air conditioning equipment and mobile air 

conditioners. Mass-balance models were used to estimate the risks from short term and long term 

exposures to ODS substitutes used in these end uses. To assess noncarcinogenic effects, 

estimated long term exposures were compared to reference concentrations. Cancer risks were 

calculated using standard risk equations. The estimated short term exposures were compared to 

interim emergency guidance levels (EGLs) developed by EPA for each substitute.

General Population Exposure. To screen risks to the general population, EPA 

considered releases from the following types of facilities: manufacturing facilities that produce 

refrigeration or air conditioning equipment, operating facilities using refrigeration or air 

conditioning equipment, service stations (mobile air conditioners only), and recycling centers 

(household refrigeration and air conditioning end uses only) or salvage yards (mobile air 

conditioners only). Model facilities were developed for each refrigeration and air conditioning 

end use. For each type of facility, conservative release estimates were multiplied by dispersion 

factors to predict fenceline concentrations of HCFC, HFC, and other chemical substitutes 

downwind of these facilities. These concentrations were then compared to estimated reference 

concentrations to screen noncancer health risks. Cancer risks were calculated using EPA's 

standard risk equation.

Atmospherics. In this analysis, two different baselines are employed to present the 

atmospheric impacts associated with each of the potential substitutes in a given end use: an 

"ideal" or "no-risk" baseline, and a "no-substitution" baseline. These two baselines bound the 

range of health effects, since the first examines impacts from a risk-free scenario and the second 

presents effects assuming continued use of all CFCs. These baselines can be summarized as 

follows:

$ "Ideal" Baseline: This baseline presents the incremental ODP risks associated 

with the use each of the potential substitutes in a given end use relative to a 

hypothetical substitute with an ODP of 0.0. In essence, this baseline presents the 

increase in ODP risks that could result from the use of the substitutes relative to a 

no risk (or ideal) baseline.
x

$ No Substitution Baseline: Under this baseline, the incremental performance of 

each substitute within an end-use is judged against continued use of Class I and 

Class II substances. In essence, this baseline presents the reduction in ODP risks 

associated with phasing out the use of the Class I compound in a given end use and 

switching to each of the potential substitutes.

EPA used the Atmospheric and Health Effects Framework (AHEF) to model the effects of 

substitutes for ODSs in the refrigeration and air conditioning sector. The framework employs the 

Vintaging Model for forecasting consumption and emissions of refrigeration and air conditioning 

substitutes. The Atmospheric Stabilization Framework (ASF) uses these emissions as a basis for 

predicting changes in ozone levels. Changes in UV-B flux are then estimated from the ASF 

output. Finally, AHEF utilizes a human health effects model to calculate skin cancer cases and 

fatalities.

VOCs. VOC emissions from the refrigeration and air conditioning end uses were 

estimated under the conservative assumption that all ODSs currently used in refrigeration and air 

conditioning equipment would be replaced with VOCs. These emissions were then compared to 

total VOC emissions from all sources at the national level.

The use of substitutes for ODSs in the refrigeration and air conditioning sector were 

assumed to result in no releases of chemicals to surface waters that could result in potential risks to 

the general population or aquatic life, nor were the substitutes expected to result in the generation 

of solid waste that could potentially result in risks to the general population.

ES.3 RISK SCREENING RESULTS

The results of EPA's risk screens are summarized briefly below and discussed in greater 

detail in the body of this report.

Atmospherics. Exhibits ES-1 and ES-2 summarize the impacts on skin cancers, 

fatalities, and cumulative Clx resulting from the use of the potential ODS substitutes in the 

refrigeration and air conditioning sectors relative to the ideal and no substitution baselines, 

respectively. Exhibit ES-1 (ideal baseline) indicates that for the vast majority of end use and 

substitute combinations the increase in skin cancers is less than 10,000 cases and the increase in 

fatalities is less than 1,000, relative to the ideal baseline. The greatest increase in skin cancers and 

fatalities results from certain substitutes examined in the MACs sector. This is due to (1) the 

significant quantities of chemical use in the MACs sector; (2) the ODPs of some of the alternatives 

examined; and importantly (3) the timing of the availability of the chemical substitutes. Exhibit 

ES-2 (no substitution baseline) indicates that virtually all of the substitutes analyzed are 

substantially less harmful to the ozone layer than continued use of CFCs.

Worker exposure. The results of EPA's analysis indicates that for the vast majority of 

end use, substitute, and operation combinations workers will not be exposed to potentially

hazardous airborne gas or vapor concentrations. Exhibit ES-3 summarizes the results for those 

scenarios where the model suggests that worker exposures exceed either the 8-hour or 30-minute 

occupational exposure limit (OEL) for the alternative refrigerant (Exhibit ES-4 summarizes the 

OELs for the potential alternative refrigerants).

In considering the implications of the results presented in Exhibit ES-3, it is important to 

note the following observations that suggest that the analytical results will overstate likely 

occupational exposures to alternative refrigerants:
xi

$ The emission estimates from the Vintaging Model used in the analysis are 

considered to be worst-case estimates.

$ The analysis does not assume the use of any local exhaust ventilation, which is 

likely to be used in manufacturing and disposal operations involving any 

significant releases. The use of properly designed local exhaust ventilation would 

likely prevent gas or vapor concentrations from exceeding the OELs most of the 

time.

$ The analysis assumes for each release scenario that the entire daily release occurs 

over a single 8-hour workday at a single location. This is not the case for many

scenarios, and particularly for manufacturing operations, where the estimated daily 

release may occur over two or three workshifts or where the release may be spread 

over two or three production lines.

$ The vast majority of the exceedances over the OELs are the result of assuming that 

there will be no recycling of HFC refrigerants. Given that such recycling is
xii

es2
xxi

EXHIBIT ES-3

SUMMARY OF ESTIMATED WORKER EXPOSURE TO ALTERNATIVE REFRIGERANTS

FOR SCENARIOS WHERE THE OCCUPATIONAL EXPOSURE LIMIT IS EXCEEDEDa

8-Hour TWAb30-Minute TWA

End-Use Sector Operation Substitute

Materialc

Predicted

Exposure (ppm) Operation SubstituteMaterialc

Predicted

Exposure (ppm)

Retail Food (Parallel 

System)

Disposal HFC-134a

HFC-125

HFC-143a

HFC-23

1,579

1,342

1,917

2,300

Disposal HFC-134a

HFC-125

HFC-143a

HFC-23

4,742

4,030

5,757

6,909

Cold Storage Warehouses Disposal HFC-152a

HFC-23

1,309

1,234

Centrifugal Chillers (Low 

Pressure)

Manufacture HCFC-123 73d

Centrifugal Chillers (High 

Pressure)

Disposal HFC-124

HFC-134a

HFC-227ea

2,271

3,050

1,647

Disposal HFC-124

HFC-134a

HFC-227ea

6,819

9,159

4,928

Industrial Process (Low 

Pressure)

Manufacture

Repair

HCFC-123

HCFC-123

54

49
xxii

EXHIBIT ES-3 (continued)

SUMMARY OF ESTIMATED WORKER EXPOSURE TO ALTERNATIVE REFRIGERANTS

FOR SCENARIOS WHERE THE OCCUPATIONAL EXPOSURE LIMIT IS EXCEEDEDa

8-Hour TWAb30-Minute TWA

End-Use Sector Operation Substitute

Materialc

Predicted

Exposure (ppm) Operation SubstituteMaterialc

Predicted

Exposure 

(ppm)

Industrial Process

 (High Pressure 

Build-Up)

Manufacture

Disposal

HFC-143a

HFC-152a

HFC-134a

HFC-152a

HFC-125

HFC-143a

HFC-23

1,293

1,016

30,840

47,661

15,740

18,375

13,490

Manufacture

Disposal

HFC-134a

HFC-143a

HFC-152a

HFC-134a

HFC-152a

HFC-125

HFC-143a

HFC-23

3,941

7,751

6,090

92,608

143,122

47,266

56,260

40,509

Large Ice Makers Repair HFC-152a 1,076

Ice Rinks Disposal HFC-134a

HFC-152a

HFC-23

4,609

7,123

2,016

Disposal HFC-134a

HFC-152a

HFC-23

13,840

21,390

6,054

Central A/C and Home 

Heat Pumps

Manufacture HFC-152a 1,332

a

Exposure levels are rounded to the nearest whole number.

b

Time-weighted average.

c One manufacturer's representative states that worker exposures to HCFC-123 during centrifugal chiller manufacture are typically 1 ppm 

or less, due to the use of exhaust ventilation.

d

The refrigerant blends analyzed for these sectors may be considered confidential business information (CBI) by the manufacturer. As a 

result, the identification of the constituents of any blend and the proportion of each constituent contained in any blend are not presented 

in this exhibit.
xxiii

EXHIBIT ES-4

OCCUPATIONAL EXPOSURE LIMITS FOR

POTENTIAL ALTERNATIVE REFRIGERANTS*

Substitute

Material WGL (ppm) EGL (ppm)

HCFC-22 1,000 5,000

HFC-23 1,000 3,000

HCFC-123 30 2,500

HCFC-124 1,000 3,000

HFC-125 1,000 3,000

HFC-134a 1,000 3,000

HFC-143a 1,000 3,000

HCFC-142b 1,000 5,000

HFC-152a 1,000 4,000

HFC-227ea 1,000 3,000

required under the Clean Air Act beginning in 1995, exposures should be below the 

OELs for these compounds.

$ The model's tendency to overstate worker exposures is further supported by 

sampling obtained for HCFC-123 refrigerants during repair operations conducted 

on low-pressure centrifugal chillers.

Finally, the analysis did not consider the use of ammonia, butane, propane, or 

perfluoropropane as alternative refrigerants. However, existing OSHA and ASHRAE standards 

governing the handling and use of these materials should serve to limit occupational exposures to 

them.

Consumer exposure. EPA's consumer exposure analysis of household refrigeration, 

household air conditioning, and mobile air conditioning equipment indicates that unless the entire 

refrigerant charge is released over a short period of time, none of the substitutes exceed EPA's 

threshold of concern for human health risk in any piece of equipment. Routine leakage and 

servicing with recycling simply will not release enough refrigerant to pose significant short-term 

or long-term risks to human health.

If the entire charge is released (due to an accident or during servicing without recycling of 

HFC-containing equipment), then the 30-minute average concentrations exceed the EGLs for 

substitutes in household air conditioning equipment only. The following factors should be 

considered when judging whether these exceedances are cause for concern:

$ Recycling at servicing will be required for the HFCs by 1995. Until then, EPA 

believes that most HFCs will be recycled anyway, because of their high cost 

relative to CFCs.
xxiv

$ Accidental releases of an entire refrigerant charge occur infrequently. The UNEP 

(1992) reports that less than 5 percent of the refrigerators and freezers have 

accidental releases of the entire charge.

$ Exposures are below levels that would raise concern for cardiotoxic effects. This 

would be true even if higher, shorter-term TWA exposures (e.g., 15-minute TWAs) 

had been used as the basis for the assessment.

General population exposure to ambient air releases. EPA's general population 

exposure analysis indicates that even with conservative screening assumptions there are no end 

uses within the refrigeration and air conditioning sectors where the use of HFCs or HCFCs as 

substitutes for CFCs will result in exposure concentrations above the chemicals' health-based 

reference concentrations for non-cancer effects. Similarly, there are no areas for which predicted 

cancer risks would be above the upper-bound cancer risk level of concern. The analysis also 

indicates that general population exposures are not of concern for ammonia, butane, propane, and 

perfluoropropane.

VOCs. EPA's analysis indicates that potential VOC emissions from all substitutes for all 

end uses in the refrigeration and air conditioning sector are likely to be insignificant relative to 

VOC emissions from all other sources.
1. INTRODUCTION

This report documents the results of the examination of human health and environmental 

risks associated with the use of substitutes for ozone depleting substances (ODSs) in the 

refrigeration and air conditioning sectors.2 This introduction provides a brief background on the 

history and philosophy of the Significant New Alternatives Policy (SNAP) program, discusses in 

general terms the types of analyses performed to screen the risks from the substitutes, and provides 

a list of the chapters that follow.

1.1 BACKGROUND

Over the past decade, a series of diplomatic and legislative efforts have taken place in 

response to growing concerns over the progressive depletion of the Earth's stratospheric ozone 

layer and its attendant health and environmental problems. The first major step was in September 

1987, when the United States and 23 other nations signed the Montreal Protocol. The original 

agreement established a schedule for reducing by half the production and consumption of eight 

specific ODSs, including CFC-11, CFC-12, CFC-113, CFC-114, CFC-115, Halon-1211, 

Halon-1301 and Halon 2402. When the parties to the Protocol met again in London in June 1990, 

they agreed to fully phase out the original eight ODSs, as well as methyl chloroform, carbon 

tetrachloride, and other fully halogenated CFCs.

Congress incorporated the requirements of the London Amendments into the Clean Air 

Act (CAA) Amendments of November 15, 1990, and in some cases went beyond the London 

requirements. Title VI of the CAA differs from the London Amendments by mandating a faster 

phaseout of methyl chloroform, a restriction on the use of hydrochlorofluorocarbons (HCFCs) 

after 2015, and a ban on the production of HCFCs after 2030. When the Parties to the Montreal 

Protocol met in Copenhagen in November 1992, they further accelerated the phaseout dates for 

many controlled substances. To implement the Copenhagen amendments and adjustments, EPA 

promulgated regulations in December 1993 that set the phaseout date at January 1, 1996 for Class 

I substances (as defined in the CAA), with the exception of halons which were subject to a 

phaseout by January 1, 1994. The regulation also includes a phaseout of methyl bromide by the 

year 2001.

Section 612 of the CAA requires EPA to develop a program to evaluate the risks to human 

health and the environment posed by alternatives to ODSs. EPA is referring to this new program 

as the Significant New Alternatives Policy (SNAP) program. The SNAP program is directed at 

fulfilling the general mandate in Section 612 of identifying acceptable and unacceptable 

substitutes for the Class I ODSs. Initial SNAP implementation involves two key activities: (1) 

developing, promulgating, and administering a regulatory program for identifying and evaluating 

substitutes, and (2) publishing a list of acceptable and unacceptable substitutes for specific end 

uses. 

 

 

2 Other sectors evaluated in separate reports are solvent cleaning, foam blowing, fire extinguishing, 

aerosols, sterilization, and adhesives, coatings, and inks.
EPA took the first major step in implementing Section 612 of the CAA on January 16, 

1992, with publication of a Request for Data and Advance Notice of Proposed Rulemaking 

(ANPRM; 57 Federal Register, p. 1984). This notice, developed with the help of the 

Stratospheric Ozone Protection Advisory Committee (STOPAC), presented the initial plan for 

implementing the SNAP program and requested producers and formulators of substitutes for 

ODSs to provide EPA with information to facilitate review of the substitutes. A Notice of 

Proposed Rulemaking was published in the Federal Register on May 12, 1993. The proposed rule 

described the proposed structure and process for administering the SNAP program and presented 

initial determinations on the acceptability of key substitutes. This Final Rule provides both the 

SNAP process and additional SNAP determinations on the acceptability of substitutes. In the 

future, substitutes will be addressed on a case-by-case basis through individual notices. In 

addition, EPA will accept petitions requesting that a substance be added or deleted from either of 

the lists.

1.2 EVALUATION OF SUBSTITUTES

To develop the lists of unacceptable and acceptable substitutes, EPA conducted a 

comprehensive screening assessment of the health and environmental risks posed by various 

substitutes in the context in which they are used. Substitutes are grouped into one or more of 

eight general sectors: refrigeration and air conditioning; solvent cleaning; foam blowing; fire 

extinguishing; aerosols; sterilization; adhesives, coatings, and inks; and tobacco expansion. 

Within each sector, substitutes are evaluated in the context of particular end uses. Examples of 

end uses within the refrigeration and air conditioning sectors include cold storage warehouse 

refrigeration systems, household refrigerators, and mobile air conditioners. EPA also determined 

the feasibility of using each substitute by assessing its production capacity and projected market 

share. Based on these analyses, EPA will identify as "unacceptable" only those substitutes that 

pose significantly higher human health and environmental risks than other available substitutes. 

EPA does not intend to restrict substitutes that are only marginally worse based on some criteria.

EPA's evaluation of each substitute in each end use is based on the following types of 

information and analyses:

 Atmospheric effects are assessed by using models to predict stratospheric ozone 

depletion. Ozone depletion is measured in terms of cumulative Clx loadings and 

increased incidence of skin cancer cases and skin cancer mortalities. Changes in 

global temperatures may result from releases of the substitutes themselves or from 

changes in fossil fuel use due to increases or decreases in energy efficiency. These 

impacts are discussed qualitatively.

 Exposure assessments are used to estimate levels of substitutes to which workers, 

consumers, the general population, and environmental receptors may be exposed, 

and over what period of time. These assessments are based on personal 

monitoring data or area sampling data if available. Otherwise, exposures are 

assessed using measured or estimated releases as inputs to mathematical models. 

Exposure assessments may be conducted for many types of releases, including 

releases in the workplace and in peoples' homes; releases to ambient air and surface 

water; and releases from the management of solid wastes.

 Toxicity data are used to assess the possible health and environmental effects from 

exposure to the substitutes. If Occupational Safety and Health Administration 

(OSHA)-approved or EPA-wide health-based criteria such as Permissible 

Exposure Limits (PELs; for occupational exposure), reference concentrations 
3

(RfCs; for noncarcinogenic effects), or cancer slope factors (for carcinogenic risk) 

are available for a substitute, exposure information is combined with this toxicity

information to determine whether there is potential for concern. Otherwise, 

toxicity data are used in conjunction with existing EPA guidelines to develop 

health-based criteria for interim use in these risk screens.

 Flammability is examined as a possible safety concern for workers and 

consumers. EPA screens flammability risk using data on flash point and 

flammability limits (e.g., OSHA flammability/combustibility classifications), test 

data on flammability in consumer applications conducted by independent 

laboratories (e.g., Underwriters Laboratories), and information on flammability

risk minimization techniques.

 Some of the proposed substitutes are volatile organic compounds (VOCs), which 

are chemicals that increase tropospheric air pollution by contributing to 

ground-level ozone formation. Local and nationwide increases in VOC loadings 

from the use of substitutes are also evaluated.

In conducting these assessments, EPA made full use of previous analyses, including the 

1990 interim assessments prepared by EPA's Office of Pesticides and Toxic Substances (OPTS) 

and the supporting documentation (full citations are given in appropriate chapters of this report). 

These analyses were modified in some cases to incorporate more recent data or new field 

experience. Where possible, EPA incorporated data submitted in response to the ANPRM and 

NPRM. Finally, these analyses assume that the regulated community is in compliance with 

applicable requirements of other statutes and regulations administered by EPA (e.g., recycling 

requirements promulgated under the CAA) and other federal agencies (e.g., enforceable workplace 

standards set by OSHA).

1.3 RISK SCREENING REPORTS FOR REFRIGERATION AND AIR 

CONDITIONING

The remainder of this package includes a series of chapters on the following topics:

 Overview of substitutes and end uses;

 Human health and environmental concern levels for substitutes;

 Atmospherics modeling (ozone depletion, global warming);

 Occupational exposure and risk screening analysis;

 Consumer exposure and risk screening analysis;

 General population exposure and risk screening analysis (ambient air); and

 VOC analysis.

Flammability is addressed within several of the chapters. Compliance costs are addressed in 

conjunction with other SNAP decisions in a separate package, as are regulatory burdens and 

effects on small businesses.
4

Finally, three of the substitutes analyzed in this report, HCFC-123, HCFC-124, and 

HFC-134a contribute to or generate trifluoroacetic acid (TFA) as an atmospheric transformation 

product. The potential ecological effects on aqueous and terrestrial ecosystems are not addressed 

in this report because of insufficient data on the toxicity of TFA and the level to which ecosystems 

may be exposed. Research efforts of the Agency in cooperation with the Alternative 

Fluorocarbons Environmental Acceptability Study (AFEAS) are underway to define the potential 

ecological risks associated with the formation of TFA in the environment.

Although there are significant uncertainties about the potential risks associated with TFA, 

and research is continuing to address these risks, a number of preliminary statements can be made 

based on the research completed to date3:

 Research indicates that virtually 100% of the HCFC-123 and HCFC-124 released 

to the environment will degrade to TFA, and suggests that approximately 25% to 

40% of HFC-134a will also degrade to TFA.

 

 

3

See Alternative Fluorocarbons Environmental Acceptability Study (AFEAS). 1991. "Kinetics 

and Mechanisms for the Reactions of Halogenated Organic Compounds in the Troposphere." 

STEP-HALOCSIDE/AFEAS WORKSHOP, Dublin. May 14-16, 1991. See also AFEAS. 1993. 

"Production, Sales, and Atmospheric Releases of Fluorocarbons Through 1992."
5

 TFA is a highly soluble acid that will exist primarily in aqueous environments 

(rain, rivers, lakes, ocean, and groundwater). Tests have shown that it is very

resistant to decomposition and will therefore reside in the environment for long 

periods of time.

 Given conservative estimates of global HCFC and HFC use and emissions, the 

environmental concentrations of TFA will be low over the next few decades. 

 Experimental results show at high concentrations TFA has low to moderate acute 

toxicity to animals and initial tests indicate that relatively high concentrations of 

TFA cause toxic effects on some plants and algae. Research to evaluate these 

effects is continuing.

 The expected environmental concentrations of TFA over the next few decades are 

unlikely to pose a significant hazard to animals or plants.

 There has been concern that TFA might degrade to MFA (monofluoroacetic acid) 

and that MFA could exist at high enough concentrations to pose health and 

environmental risks. Research to date has identified no environmental process 

that would convert TFA to MFA. Research to elucidate all the degradation 

pathways for TFA, including potential pathways to MFA is continuing.

EPA is closely monitoring the research efforts underway with respect to TFA, and will 

assess the long term ecological risks associated with this compound when the research is 

completed. As noted above, research completed to date has not uncovered any risks that warrant 

the implementation of measures to control atmospheric concentrations of TFA. If such risks are 

identified in the future, the Agency will re-assess its position on TFA and evaluate measures to 

mitigate such risks.
2. OVERVIEW OF SUBSTITUTES AND END USES

2.1 END USES

The refrigeration industry was the first to make widespread use of CFCs after this class of 

chemical compounds was discovered in the 1930's. In 1990, refrigeration and air conditioning 

accounted for almost 22 percent of the total use of Class I substances in the United States. There 

are over 500 million pieces of refrigeration and air conditioning equipment that use these 

chemicals as the working fluids in a vapor compression cycle.

Many Class I substances exhibit desirable thermophysical properties for use in 

refrigeration cycles. They are relatively nontoxic, nonflammable, and inexpensive to produce B

characteristics that have contributed to their appeal as refrigerants. CFC-12 is the most widely

used refrigerant, with applications in mobile air conditioners (MACs), household refrigerators and 

freezers, various appliances, chillers, retail food refrigeration equipment, cold storage warehouses, 

refrigerated transport systems, and industrial equipment. CFC-11 is most commonly used to 

provide cooling for large buildings, while CFC-115, as a component in the refrigerant blend 

R-502, is used for low temperature applications in a variety of sectors. CFC-113 and CFC-114 

are used in special applications chillers.

Of the Class II controlled substances, HCFC-22 is the most common refrigerant in small to 

medium size air conditioning systems, and some types of retail food and industrial process 

refrigeration systems.

EPA has divided the refrigeration and air conditioning sector into the following general 

end uses:

 Retail Food Systems: These include stand alone refrigeration cases found in small 

markets, convenience stores, restaurants and other food establishments, large 

parallel systems found in supermarkets, and HCFC-22 systems found in a wide 

variety of retail and service establishments;

 Cold Storage Systems: Public and private facilities used to store meat, produce, 

dairy products, frozen foods, and other perishable goods. These systems 

refrigerate warehouses of varying sizes and include high pressure and low pressure 

systems;

 Chillers: These are large commercial air conditioning systems used to cool office 

buildings, shopping malls, and other large indoor spaces. End uses modeled are 

CFC-11 (low pressure) chillers, CFC-12 centrifugal chillers, CFC-12 reciprocating 

chillers, CFC-114 centrifugal chillers, and CFC-500 centrifugal chillers;

 Industrial Process Refrigeration: Refrigeration systems used in the chemical, 

pharmaceutical, petrochemical, and other manufacturing and food processing 

industries. These include both packaged and built-up systems used in 

manufacturing processes as well as extra-large ice makers;
 Ice Skating Rinks: There are several different types of ice rink systems, but all are 

grouped into one end use in this analysis;

 Ice Makers: These include small, medium, and large ice makers used by a number 

of entities, including restaurants and hotels;

 Household and Light Commercial Air Conditioning: These include window units, 

packaged terminal air conditioners, central air conditioners, direct expansion 

commercial air conditioners, and heat pumps used for space cooling and heating in 

homes and businesses. All systems in this end use currently use HCFC-22;

 Refrigerated Appliances: These include household refrigerators and freezers, 

water coolers, vending machines, and dehumidifiers. Most currently use CFC-12 

as a refrigerant, but there are some CFC-502 units in existence;

 Refrigerated Transport Systems: These include systems designed to refrigerate 

materials in transit. They are found in trucks, trains, and ships; and

 Mobile Air Conditioning: This end use includes systems installed in motor 

vehicles for the comfort of occupants.

Industry has invested heavily in the search for suitable alternative refrigerants that exhibit 

the favorable characteristics of the controlled substances, but that do not contribute to stratospheric 

ozone depletion or global warming. The hydrochlorofluorocarbons (HCFCs) and 

hydrofluorocarbons (HFCs) have received the most attention, along with expanded use of 

traditional refrigerants such as ammonia and hydrocarbons. In many cases the most promising 

solution appears to be a blend of refrigerants. Despite great progress, the suitability of many

replacements is still uncertain. Toxicity concerns, high ozone depletion potentials, or 

flammability may limit the ultimate attractiveness of potential substitutes in many applications 

when testing is completed. The 1991 report by UNEP's Refrigeration, Air Conditioning, and 

Heat Pumps Technical Options Committee contains detailed information about the status of 

alternative refrigerants in various applications.

EPA believes that HCFCs have an important role to play as transitional refrigerants, both in 

retrofit applications and in new equipment. HCFCs have the disadvantage that they do contribute 

to the destruction of stratospheric ozone, although to a much lesser extent than CFCs. HFCs have 

ozone depletion potentials (ODPs) of zero, but their practical application is years away in many 

cases. The interim use of HCFCs, until such time as safer alternatives are available, will allow 

industry to move away from CFC refrigerants more rapidly. EPA believes that this approach will 

have greater environmental benefits than permitting the continued use of CFCs until equipment 

that uses HFCs becomes available.

2.2 ALTERNATIVE REFRIGERANTS

2.2.1 HCFCs

HCFCs are chemically similar to CFCs except that they contain hydrogen in addition to 

chlorine and fluorine. HCFC-22 has been used as a refrigerant for many years. It is the primary 

refrigerant used in small to medium sized air conditioners and chillers, and has found increasing 

application in medium temperature retail food refrigeration systems. HCFC-123 holds promise 

as the primary retrofit option for CFC-11 in low pressure centrifugal chillers. HCFC-124 has 
8

potential applications in blends for many types of refrigeration equipment and, as a pure 

refrigerant, has been suggested as a replacement for CFC-114 in high pressure centrifugal chillers.

Because they contain hydrogen, the HCFCs break down more easily in the atmosphere, and 

therefore have lower ODPs. Their global warming potentials are lower than either the CFCs or 

the HFCs. Production of HCFCs is controlled by the Clean Air Act Amendments of 1990. 

Beginning in 2015, it will be unlawful to produce HCFCs for uses other than in equipment 

manufactured before 2020. Beginning in 2030, it will be unlawful to produce HCFCs, except for 

certain purposes that are exempted.

Because their thermophysical properties are, in many cases, similar to CFCs, equipment 

designed to use CFCs can sometimes be retrofitted to operate with HCFCs. As noted above, EPA 

believes that HCFCs will play an important role as transitional refrigerants. There are clear 

environmental benefits to be gained by allowing their use until better substitutes are developed. 

2.2.2 HFCs

HFCs do not contain chlorine and do not contribute to destruction of stratospheric ozone. 

Many, however, have relatively high greenhouse gas potentials and contribute to global warming. 

Although a few HFCs have been in use for some time (HFC-152a is a component in the azeotropic 

blend R-500, used in smaller tonnage reciprocating equipment and large tonnage centrifugal 

equipment), the potential for HFCs as a replacement for CFCs has only recently been investigated. 

HFC-134a and HFC-152a hold the most promise as single-substance replacements for Class I and 

Class II refrigerants. HFC-143a and HFC-125, as parts of blends, have been considered as 

substitutes for R-502 in low temperature refrigeration applications. HFC-227ea has possible 

applications as a refrigerant in mixtures used in high pressure centrifugal chillers. HFC-23 and 

HFC-32, when used in blends with other chemicals, have been proposed as a potential substitute 

for certain HCFC-22, CFC-13, and R-503 end-uses.

2.2.3 Hydrocarbons

Propane, ethane, propylene, and, to some extent, butane are used as refrigerants in 

specialized industrial applications, primarily oil refineries and chemical plants, where they are 

frequently available as part of the process stream and where their use contributes only slightly to 

the incremental risk of fire or explosion. These industrial systems are specially designed to meet 

rigid requirements for reliability, durability, and safety. ASHRAE Standard 15, Safety Code for 

Mechanical Refrigeration, and Standard 34, Refrigerants, are incorporated into building codes in 

most of the U.S. These standards limit the use of flammable refrigerants in many applications. 

Perfluoropropane and other perfluorocarbons (PFCs) have potential applications in the 

refrigeration sector as well.

2.2.4 Ammonia

Ammonia has been used as a refrigerant in vapor compression cycles for more than 100 

years. It is by far the refrigerant of choice in many food processing and industrial applications, 

such as the meat packing, chicken processing, dairy, frozen juice, brewery, and cold storage 

industries. It is also widely used to refrigerate holds in fishing vessels. Industrial process 

refrigeration equipment uses rotary screw or reciprocating compressors. Ammonia's main 

application is when moderate to low temperatures are required. Ammonia has a characteristic 

pungent odor, excellent refrigerant properties, is low in cost, and has no long-term environmental 

drawbacks. It is moderately flammable and toxic, however, but it is not a cumulative poison. 
9

Occupational Safety and Health Administration (OSHA) standards specify that the maximum 

allowable concentration of ammonia for an eight-hour working exposure is 50 ppm.

2.2.5 Chlorine

Chlorine has been proposed as a Class I substitute refrigerant for use in chlorine 

liquification, a processing step in the manufacture of the chemical. When chilled below its

boiling point, chlorine can be stored as a liquid at atmospheric pressure, a method that for safety 

reasons is much preferred to storing the chemical as a pressured gas at ambient temperatures. 

Compatibility of the refrigerant with liquid chlorine is critical because of chlorine's high reactivity; 

CFC-12 has been widely used because it is nonreactive with chlorine.

Chlorine compressors would be specialized units made to resist chemical attack by liquid 

and gaseous chlorine. Because a chlorine refrigeration system would use part of the process 

stream as the refrigerant, the proposed use of chlorine as a refrigerant is analogous to that of 

hydrocarbon refrigerants in the oil and gas industry. EPA has determined that, if the refrigeration 

system is placed so that any leakage or losses of chlorine would be contained and neutralized by

the process safety mechanisms, chlorine can be used safely in these specialized applications.

2.2.6 Potential Substitutes that Manufacturers have Submitted as Confidential Business 

Information

A few substitutes that may be used in certain refrigeration and air conditioning end uses 

have been submitted by their manufacturers as confidential business information. As a result, the 

identity of these substitutes are not revealed in this analysis. The results of the risk analyses for 

these compounds are presented under the following identities: R200b through R200i and 

HCFC/HFC/Fluoroalkane Blend A.

2.3 ALTERNATIVE TECHNOLOGIES

2.3.1 Absorption Refrigeration Systems

Absorption refrigeration systems are the only major existing alternative to systems based 

on vapor compression cycles. Ammonia is also used in absorption refrigeration and air 

conditioning systems. Small ammonia refrigeration units are popular in recreational vehicles and 

in some household applications as they need no electrically driven mechanical compressor, relying 

instead on a propane flame as an energy source. Small refrigerators using absorption technology 

are produced for use in hotel rooms, where the focus is on their silent operation rather than the lack 

of a suitable supply of electricity. Small absorption type systems use hydrogen to maintain a 

system pressure high enough to allow the ammonia refrigerant to evaporate at low pressure and 

temperature (and condense at room temperature), and are constructed to withstand high internal 

operating pressures. The absorption mechanism itself is a sealed unit, which usually needs no 

servicing over its operating life.

Commercial ammonia absorption systems are used for air conditioning comfort cooling, 

particularly in instances where waste heat is available. As with all chillers, these produce chilled 

water, which is circulated to the space being cooled. Lithium bromide is also used in commercial 

absorption systems, where it serves as an absorbent. Such systems operate at very low pressure to 

allow water to act as a refrigerant. Lithium bromide is a relatively nontoxic, nonflammable, 
10

nonexplosive, chemically stable compound. Both types of absorption chiller systems have 

traditionally been competitors to electrically driven CFC chillers.

2.3.2 Evaporative Cooling

 Evaporative cooling is another technology that could be an alternative to CFC- and 

HCFC-based vapor compression systems in some applications. Three types of EC systems exist: 

direct, indirect, and desiccant-assisted. In direct EC, the airstream temperature is decreased by

bringing the air into direct contact with liquid water. Because it humidifies when it cools, direct 

evaporative cooling can give customer comfort only where the ambient air is hot and dry, such as 

in the southwestern parts of the United States. Indirect systems use a heat exchanger between the 

water and the airstream, and desiccant-assisted systems use a desiccant to dry the air before it is 

exposed to water. These new developments have greatly expanded the applicability of EC to 

include the entire U.S.

Contrary to vapor compression systems, evaporative coolers do not require compressors 

and consequently can offer considerable energy savings. Evaporative coolers have been used for 

many years to provide cooling for comfort and for a variety of industrial and agricultural 

applications. They are energy-efficient, inexpensive to purchase, and have low operating costs.
3. TOXICITY REFERENCE VALUES FOR SUBSTITUTES

To assess potential health risks from exposure to substitutes for ozone-depleting 

substances (ODSs) in the refrigerants sector, EPA identified or developed toxicity reference values 

for each substitute. These values include occupational exposure limits, reference concentrations, 

and cancer slope factors. The toxicity reference values were compared to or combined with 

predicted exposure concentrations to estimate risks to workers, consumers, and the general 

population, as described in subsequent chapters of this report.

This chapter first discusses EPA's general approach for identifying or developing the 

toxicity reference values for substitutes examined in the SNAP background documents. Section

3.1 discusses occupational exposure limits, and Section 3.2 discusses general population toxicity

reference values. Both of these sections pertain to the inhalation route of exposure.

This chapter concludes by presenting the most recent toxicity reference values available 

for the substitutes covered in the refrigerants sector at the time of publication of this background 

document (Exhibit 3-1). The list of substitutes presented in Exhibit 3-1 is not all inclusive; 

however, the Agency believes that the substitutes selected for this review are representative of the 

types of agents that could replace ODSs in this sector. The Agency has also included in this 

screen replacement chemicals that may have high toxicity potential to ensure that the assumptions 

used in the subsequent hazard assessments are valid and conservative.

3.1 OCCUPATIONAL4(INHALATION) EXPOSURE LIMITS

Allowable occupational exposure limits (OELs) for continuous and short-term exposure, 

denoted as the workplace guidance level (WGL) and emergency guidance level (EGL), 

respectively, are used to examine potential risks to workers. Whenever available, the WGLs and 

EGLs are based on OELs developed by the Occupational Safety and Health Administration 

(OSHA), the National Institute for Occupational Safety and Health (NIOSH), the American 

Conference of Governmental Industrial Hygienists (ACGIH), or the American Industrial Hygiene 

Association (AIHA). 

The Occupational Safety and Health Administration (OSHA) is a governmental agency

within the Department of Labor that sets enforceable occupational standards. Limits set by

OSHA include permissible exposure limits (PELs

5

) and short-term exposure limits (STELs). The 

PEL is an 8-hour time-weighted average (TWA) airborne exposure limit that is designed, to the 

extent feasible, to reduce a significant risk of material impairment of health or functional capacity 

associated with exposure to a hazardous substance. The STEL is the employee's 15-minute TWA 

exposure that should not be exceeded at any time during a work day. It is designed to protect 

workers from experiencing adverse acute health effects such as respiratory irritation, eye irritation, 

 

 

4

In some cases, these occupational exposure limits were also used to assess general population/consumer risk.

 

5 On July 7, 1992, the 11th Circuit Court of Appeals overturned permissible exposure limits (PELs) for 428 chemicals that were set by 

OSHA in January 1989. Employers are now legally bound to observe the 1971 PELs codified in 29 CFR 1910.1000. EPA has, however, 

decided to continue using the January 1989 proposed PELs for the purposes of the SNAP risk screen because these values are more 

representative of ACGIH TWA threshold limit values (TLV-TWAs) and AIHA workplace environmental exposure levels (WEELs), and 

cover a wider range of chemicals.
and narcosis. It must be noted that because OSHA's exposure limits are legally enforceable, 

OSHA must consider a variety of factors including technologic and economic feasibility in 

establishing them. Thus, the limits set by OSHA do not solely reflect the toxicological properties 

of the material.


13

Exhibit 3-1


14

Exhibit 3-1 (cont.)
15

The National Institute for Occupational Safety and Health (NIOSH), a governmental 

institute under the jurisdiction of the Department of Health and Human Services, develops 

recommended exposure limits (RELs) that are non-enforceable. Unlike OSHA, NIOSH is not 

constrained by issues of technical or economic feasibility or significance of risk when deriving 

RELs. NIOSH also estimates concentrations of chemicals that are immediately dangerous to life 

and health (IDLH), which represents "the maximum concentration from which. . . one could 

escape within 30 minutes . . . without experiencing any escape-impairing (e.g., severe eye 

irritation) or irreversible health effects" (NIOSH 1990).

The American Conference of Governmental Industrial Hygienists (ACGIH) is a 

non-governmental limit setting body. ACGIH's non-enforceable TWA threshold limit values 

(TLV-TWAs) are similar to OSHA's PELs. ACGIH does not formally analyze for technical 

feasibility, but there appears to be some implicit recognition of feasibility since TLVs are set to be 

protective for most workers but not so low as to be "unduly restrictive." ACGIH TLVs provided 

much of the basis for OSHA's 1989 air contaminant standards.

The American Industrial Hygiene Association (AIHA) is also non-governmental. The 

AIHA workplace environmental exposure levels (WEELs) are like the TLVs in that the 

justification of a particular WEEL is based predominantly on toxicological information rather than 

feasibility. However, it is likely that feasibility is considered implicitly since the WEELs are 

limits that are protective and practical.

The long-term occupational exposure limits (WGLs) used for the SNAP risk screening 

assessments are based on OSHA PELs, NIOSH RELs, ACGIH TLV-TWAs, or AIHA WEELs, if 

available. The short-term occupational exposure limits (EGLs) are based on OSHA STELs or 

NIOSH IDLHs, if available. EPA recognizes that in an industrial setting OSHA STELs are 

typically much lower than IDLHs and other emergency guidance levels, and that exposure at the 

OSHA STEL is not a situation requiring emergency corrective action. Therefore, using OSHA 

STELs as EGLs is a conservative way to screen risks from short-term exposure to chemicals.

If OSHA, ACGIH, NIOSH, or AIHA OELs were not available for a substitute, and WGLs 

or EGLs were considered important for the risk screening assessment, they were estimated by

EPA. Although the estimated WGLs are intended to be analogous to OSHA PELs, they are 

different in that PELs are developed by a regulatory process and incorporate complex decision 

criteria such as technological feasibility. In estimating WGLs, EPA took into consideration the 

characteristics of workers who are healthier and younger than the general population, and 

experience intermittent rather than continuous exposure. Where appropriate, WGLs were 

estimated to be ten times greater than the suggested reference concentration (see Section 3.2.1). 

If the resulting estimate was greater than the 1,000 ppm TLV-TWA set by ACGIH (1986) ". . . as 

a guide for good hygiene practice for vapors of low toxicity" (i.e., the "good housekeeping" limit), 

then the latter was used for the risk screening analysis.

The EGL estimate is similar to the NIOSH IDLH (i.e., the maximum concentration from 

which one could escape within 30 minutes without experiencing escape-impairing or irreversible 

health effects). It also resembles the emergency exposure guidance level (EEGL) and the 

short-term public emergency guidance level (SPEGL) suggested by NRC (1986) and the 

emergency response planning guideline suggested by AIHA (1989). In instances when a 

substitute has an OEL but the available toxicological data were not sufficient to develop a STEL, 

the ACGIH excursion limit recommendation as stated below was used to estimate the EGL:
16

"Excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more 

than a total of 30 minutes during a work-day, and under no circumstances should they 

exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded" (ACGIH, 

1992).

Thus, EGLs can range from three to five times the OEL.

In the event of a fire, explosion, or catastrophic emission, the EGL estimates for most of the 

HCFCs and HFCs and several other chemicals in this sector are based on the 

lowest-observed-adverse-effect level (LOAEL) or on the no-observed-adverse-effect level 

(NOAEL) for cardiotoxicity in epinephrine-sensitized dogs because the primary concern for acute 

high-level exposure to these compounds is cardiotoxicity. Cardiac sensitization is of particular 

interest in these acute, episodic exposures because human heart arrhythmias and sudden death 

resulting from overexposure to halons, CFCs, and other halogenated hydrocarbons have been 

documented in workplace settings and in volatile substance abuse (e.g., glue sniffing). As 

defined by the Agency, cardiotoxicity is the ability of a compound to cause serious and sometimes 

fatal cardiac arrhythmia, and is best evaluated by exposing the appropriate species, usually the 

dog, to an agent by inhalation in the presence of epinephrine (Rubenstein and Bellin 1993). The 

Agency is using these values in the SNAP risk screen to ensure protection of the worker 

population. 

The protocols used to determine the cardiotoxic LOAEL and NOAEL concentrations for 

each agent are conservative; they entail measurement of cardiotoxic effects in animals made more 

sensitive to these effects by the administration of epinephrine. The administered doses of 

epinephrine are just below the concentrations at which epinephrine alone would cause 

cardiotoxicity in the experimental animal, and are approximately ten times greater than the 

concentration a human being would likely secrete under stress. Thus, the estimated LOAELs and 

NOAELs would be conservative for humans even in high-stress situations.

EPA is adopting OSHA standard (29 CFR 1910, subpart L) section 1910.162 arising from 

the cardiac sensitization induced by Halon 1301, and is basing its risk assessment decisions for the 

substitutes that induce cardiotoxicity upon this standard. Under safe use conditions for Halon 

1301 (29 CFR 1910.162), the exposure limits, based upon the length of time it takes to evacuate, 

can be summarized as follows:

$ Where egress takes longer than 30 seconds but less than one minute, the employer 

shall not use the agent in a concentration greater than its LOAEL for cardiotoxicity

(e.g., 100,000 ppm for Halon 1301).

$ Agent concentrations greater than the LOAEL for cardiotoxicity are only permitted 

in areas not normally occupied by employees provided that any employee in the 

area can escape within 30 seconds. The employer shall assure that no unprotected 

employees enter the area during agent discharge.

$ Where egress from an area cannot be accomplished within one minute, the 

employer shall not use this agent in concentrations exceeding its NOAEL for 

cardiotoxicity (e.g., 75,000 ppm for Halon 1301).
17

In addition, EPA recognizes that agents should not be used at a concentration that would 

significantly displace oxygen in the lungs. Since most of the refrigerant substitutes are gaseous, 

heavier-than-air compounds, following a leak or catastrophic emission, they may tend to pool near 

the ground, (i.e. in the breathing zone). These agents are, in the main, colorless with minimal 

odor and little toxicity or irritant effect, therefore, they can lead to asphyxiation by oxygen 

displacement, if the unwary person inadvertently walked into an area of oxygen depletion.

Under the SNAP risk screen, EPA is only intending to set conditions for the safe use of 

refrigerant substitutes in the workplace until OSHA incorporates specific language addressing 

gaseous agents into the OSHA regulation. These general conditions will no longer apply once 

OSHA establishes applicable work place requirements.

Where appropriate, the Agency also based its analysis of short-term exposures to 

consumers and the general population on these cardiotoxic levels.

3.2 GENERAL POPULATION/CONSUMER (INHALATION) TOXICITY 

REFERENCE VALUES

For the refrigerants sector, risks to the general population and consumers were screened for 

short-term and/or long-term exposure scenarios. Risks from short-term exposure were screened 

using the EGLs and cardiotoxic LOAELs and NOAELs discussed in the previous section. This 

section discusses EPA's general approach for identifying and developing toxicity reference values 

applicable to chronic (i.e., lifetime) exposure: verified or interim reference concentrations (RfCs) 

for noncarcinogens and cancer slope factors (SFs) for carcinogens.

3.2.1 Reference Concentrations (RfCs)

When possible, the RfC verified by the Agency's RfD/RfC Work Group, whether or not it 

has been listed on the Agency's Integrated Risk Information System (IRIS) database, was used to 

assess the risk from long-term exposure to ODS substitutes in the SNAP background assessments. 

The RfC is designed to protect the general population against adverse systemic (i.e., noncancer) 

effects, and is defined as:

"An estimate (with uncertainty spanning perhaps an order of magnitude) of a daily

exposure to the human population (including sensitive subgroups) that is likely to be 

without appreciable risk of deleterious effects during a lifetime. The inhalation reference 

concentration is for continuous inhalation exposures and is appropriately expressed in units 

of mg/m3" (U.S. EPA 1990).

However, when verified RfCs were not available, interim RfCs were used to evaluate risks 

associated with chronic exposure to ODS (listed in decreasing order of preference):

$ Currently undergoing verification by the Work Group;

$ Not yet undergoing verification but contained in the Agency's Health Effects 

Assessment Summary Tables (HEAST; U.S. EPA 1992);

$ Estimated from other data for the substitute; or
18

$ Estimated based on surrogate limits.

The remainder of this section discusses the interim RfCs derived from other data for the substitute 

or estimated based on surrogate limits.

RfCs Estimated From Other Data

In the absence of a verified RfC or an RfC pending verification by the Agency's RfD/RfC 

Work Group, EPA calculated an interim RfC using the methods specified in EPA's Interim 

Methods for Development of Inhalation Reference Concentrations (U.S. EPA 1990). Since 

adequate human data were not available to calculate RfCs for the proposed substitutes that did not 

already have RfCs, data obtained from animal inhalation toxicity experiments served as the basis 

for estimating the RfCs. This approach was adopted in developing an interim RfC for HFC-143a. 

For the purposes of the SNAP risk screen, the interim RfC that has been estimated for HFC-143a 

was based on limited animal data. The Agency's RfD/RfC Work Group reviewed the quality and 

quantity of the animal data and determined that the available information was inadequate to derive 

an RfC. The compound's interim RfC is, therefore, currently listed as "not verifiable". In 

general, the verification process requires the existence of a sizeable body of information. Ideally, 

this should include two well-conducted chronic inhalation studies, one reproductive study, and 

two developmental toxicity studies in different species. The term "not verifiable" does not imply 

that if only limited data are available that these data are technically deficient. The Agency will 

develop the verified RfC for HFC-143a when these data become available; use of the interim value 

should be restricted solely to the SNAP risk screen.

If adequate animal inhalation toxicity data were unavailable for a substitute, the interim 

general population RfC was estimated by extrapolation from oral references doses (RfDs) or oral 

NOAELs or LOAELs. According to the Interim Methods for Development of Reference 

Concentrations, such route-to-route extrapolation can be performed if pharmacokinetic data, 

including measurements of absorption efficiency and comparative excretion data (when the 

associated metabolic pathways are equivalent) are available for both routes of interest, and 

comparative systemic toxicity data indicate equivalent effects by each route of interest. However, 

the Interim Methods stipulate that oral data should not be used to estimate inhalation exposure 

limits when the following conditions exist:

(1) When groups of chemicals are expected to have different toxicity by the two routes 

of exposure (e.g., metals, irritants, and sensitizers);

(2) When a first-pass effect is expected by the liver, or when the pulmonary system was 

not adequately studied in the oral studies;

(3) When a pulmonary effect is established, but dosimetry comparison cannot be 

clearly established between the two routes; and

(4) When short-term inhalation studies or in vitro studies indicate potential 

portal-of-entry effects at the lung, but studies themselves are not adequate for RfC 

development.

The appropriate data to assess these conditions were not available for substitutes requiring a 

route-to-route extrapolation. Therefore, the interim RfCs that were estimated by extrapolation 
19

from oral data would most likely be considered "not verifiable" by the Agency's RfD/RfC Work 

Group. However, in the absence of adequate data and in need of a chronic reference toxicity

value for the purpose of the SNAP risk screens, extrapolation from oral data was nevertheless 

performed according to the following procedures:

(1) Oral RfDs (expressed in mg/kg/day) were converted to inhalation RfCs (expressed 

in mg/m3) by multiplying the RfD by the default assumption for average human 

body weight (70 kg) and dividing by the default assumption for average human 

breathing rate (20 m

3

/day) (EPA 1988).

(2) Alternatively, in the absence of adequate experimental inhalation toxicity data, 

RfCs for some substitutes were estimated by converting the OEL for that substitute 

(or a suitable surrogate, as discussed below) to a general population exposure limit. 

For example, the aliphatic hydrocarbon isobutane is best represented by pentane. 

The OSHA PEL for pentane is 1,800 mg/m3. This value is based on an 8-hour 

TWA worker exposure over a 40-hour work week. To extrapolate to a threshold 

for long-term continuous general population exposure, the PEL was multiplied by a

factor of 10 m3/20 m3(assuming that 10 m3are inhaled in an 8-hour day by a 

healthy worker, extrapolated to 20 m3in a 24-hour day by the general population) 

(Jarabek and Hasselblad 1991), and then divided by an uncertainty factor of 1,000 

to account for sensitive subpopulations and other uncertainties.

Interim RfCs Based on Surrogate Limits

For some of the substitutes, there are neither RfCs nor adequate experimental inhalation 

toxicity data, oral RfDs, oral data, or OELs from which to estimate an RfC. In these cases, 

exposure limits for a surrogate such as HFC-134a, the surrogate for several HFCs in this sector, 

was used. Surrogates were chosen by structure-activity relationship (SAR) analysis to provide 

the worst-case/most conservative estimate for the exposure limit. SAR is used to predict the 

biological activity of an untested compound based on an examination of analogous chemicals with 

well-documented health or environmental effects data.

SAR has been an important tool in guiding the development of new chemicals and drugs 

for many years. EPA has used SAR in assessing new chemicals prior to their manufacture or 

importation under the Premanufacture Notice Program. Also, the pharmaceutical industry has 

used SAR to assist in the design and synthesis of new drugs. 
20

3.2.2 Cancer Slope Factors

The cancer slope factor (SF) is used to estimate the upper-bound risk for cancer. Because 

chemicals that produce cancer are assumed not to show a threshold for their effects, the observed 

threshold level (i.e., the NOAEL) is not used in the calculation of the cancer SF. Rather, the slope 

of the dose-response for the effect is used to extrapolate levels at which the risk of the effect is 

small. It has been argued that the dose-response function for carcinogenicity could be linear and 

that it is unlikely to exceed linearity in the low-dose region. Thus the model chosen to extrapolate 

low-dose effects from the much higher doses at which effects are observed assumes low-dose 

linearity for cancer production. EPA guidelines (U.S. EPA 1986) recommend that, in absence of 

adequate information to the contrary, the linearized multistage procedure should be used for the 

extrapolation. This model expresses upper confidence limits on cancer risk as a linear function of 

dose in the low-dose range. Cancer SFs are estimated by fitting the model to experimental animal 

carcinogenicity data using the maximum likelihood method. In addition, an upper bound on the 

dose-response curve is calculated, reflecting uncertainty of extrapolating the curve to low doses at 

which human exposures are anticipated to occur. This upper bound can be considered to 

represent the largest reasonable linear extrapolation to low doses consistent with the data. The 95 

percent statistical upper limit on the linear term, q1, is referred to as the q1*, or the SF.

The SNAP cancer risk estimates were based on cancer SFs that have been verified by 

EPA's Cancer Risk Assessment Verification Endeavor (CRAVE) Work Group and are contained 

in IRIS. If these were unavailable, a second choice was SFs that have not yet been verified but are 

contained in HEAST (U.S. EPA 1992). The interim SFs for HCFC-22 and HCFC-123 were 

estimated using raw data from recently completed chronic inhalation cancer bioassays, according 

to the methods recommended in the EPA Risk Assessment Guidelines (U.S. EPA 1986).
21

REFERENCES

ACGIH. 1986. Documentation of the Threshold Limit Values and Biological Exposure Indices. 

Fifth Edition. 

ACGIH. 1992. 1992-1993 Threshold Limit Values for Chemical Substances and Physical 

Agents and Biological Exposure Indices. 

AIHA. 1989. Concepts and Procedures for the Development of Emergency Response Planning 

Guidelines (ERPGs). ERPG Committee. 

Jarabek, A.M. and V. Hasselblad. 1991. Inhalation Reference Concentration Methodology: 

Impact of Dosimetric Adjustments and Future Directions Using the Confidence Profile 

Method. Presented at 84th Annual Meeting and Exhibition, Vancouver, B.C. June 

16-21, 1991.

NIOSH. 1990. NIOSH Pocket Guide to Chemical Hazards. NIOSH Pub. No. 90-117. US 

DHHS.

NRC. 1986. Criteria and Methods for Preparing Emergency Exposure Guidance Level 

(EEGL), Short-term Public Emergency Guidance Level (SPEGL), and Continuous 

Exposure Guidance Level (CEGL) Documents. Committee on Toxicology. National 

Academy Press, Washington, DC.

Rubenstein, R. and J.S. Bellin. 1993. Short Duration High-Level Exposure to Halon 

Substitutes: 

Potential Cardiovascular Effects. Presented at Halon Alternatives Technical Working 

Conference, Albuquerque, NM, May 11B13, 1993.

U.S. EPA. 1992. Health Effects Assessment Summary Tables. Annual Update. 

Environmental Criteria and Assessment Office, Office of Health and Environmental 

Assessment. Cincinnati, OH. OHEA ECAO-CIN-821.

U.S. EPA. 1990. Interim Methods for Development of Inhalation Reference Concentrations. 

Review Draft. August 1990. Environmental Criteria and Assessment Office, Office of 

Health and Environmental Assessment, Research Triangle Park, NC. EPA 

600/8-90/066A.

U.S. EPA. 1988. Recommendations for and Documentation of Biological Values for Use in 

Risk Assessment. February 1988. Office of Health and Environmental Assessment, 

Environmental Criteria and Assessment Office, Cincinnati, OH.

U.S. EPA. 1986. The Risk Assessment Guidelines of 1986. Office of Health and 

Environmental Assessment. Washington, DC. EPA/600/8-87/045.
4. ATMOSPHERICS MODELING

4.1 INTRODUCTION

EPA has conducted a risk screen of possible alternatives to Class I ozone depleting 

substances (ODSs) as part of its implementation of Section 612 of the Clean Air Act Amendments 

of 1990. Class I substances include chlorofluorocarbons (CFCs), halons, carbon tetrachloride, 

and methyl chloroform (MCF). Class I ODSs deplete stratospheric ozone and may contribute to 

global warming. These atmospheric changes have potentially serious consequences for human 

health and the environment. The depletion of stratospheric ozone increases the amount of 

biologically active ultraviolet radiation (UV-B) at the earth's surface. Among the consequences 

of increased UV-B are the increased incidence of cataracts and skin cancers, damage to plants and 

animals, and damage to polymers (chemical compounds often used in plastics, paints, and 

coatings). This chapter presents estimates of the potential atmospheric and human health effects 

of the alternatives available to replace Class I compounds in the refrigeration and air conditioning 

sector.

The remainder of this chapter is divided into the six following sections: Section 4.2 

presents an overview of the refrigeration and air conditioning sector, including a description of the 

major end uses; Section 4.3 summarizes the potential replacements for Class I compounds in the 

refrigeration and air conditioning sector; Section 4.4 describes the baseline for the analysis; 

Section 4.5 details the modeling framework used to quantify the atmospheric and human health 

impacts of the alternatives; Section 4.6 presents the results of the analysis; and Section 4.7 presents 

a qualitative discussion of global warming and global warming potentials.

4.2 DESCRIPTION OF REFRIGERATION AND AIR CONDITIONING END USES

CFCs are used as refrigerants in numerous refrigeration and air conditioning applications. 

For the purposes of this analysis, the refrigeration and air conditioning sector was divided into 

several end uses to facilitate appropriate comparisons between possible substitutes. Two general 

principles define how equipment types were classified into the various end uses: (1) all 

equipment types in an end use employ roughly comparable refrigeration technologies (e.g., low 

and high pressure cold storage warehouse systems are separated ); and (2) all equipment types in 

an end use serve the same general consumer or industrial purpose (e.g., ice skating rinks and 

parallel retail food systems form separate end uses).

The advantage of this end use classification is that substitutes applicable to a given end use 

will typically be able to be used in all segments of that end use. A consequence, however, is that 

some end uses are considerably larger than others. For example, all high-pressure industrial 

process refrigeration systems form one end use, while another end use consists only of CFC-12 

reciprocating chillers.

While the principal focus of this analysis is to evaluate alternatives to Class I substances, 

many end uses in the refrigeration and air conditioning sector primarily use HCFC-22 (a Class II 

compound). In order to comprehensively examine the health and environmental effects of 
substitutes throughout this sector, HCFC end uses were analyzed in the same manner as CFC end 

uses. 

The end use categories are as follows:

 Retail Food Systems: These include stand alone refrigeration cases found in small 

markets, convenience stores, restaurants and other food establishments, large 

parallel systems found in supermarkets, and HCFC-22 systems found in a wide 

variety of retail and service establishments.

 Cold Storage Systems: These systems refrigerate warehouses of varying sizes and 

include high pressure and low pressure systems.

 Chillers: These are large commercial air conditioning systems used to cool office 

buildings, shopping malls, and other large indoor spaces. End uses modeled are 

CFC-11 (low pressure) chillers, CFC-12 centrifugal chillers, CFC-12 reciprocating 

chillers, CFC-114 centrifugal chillers, and CFC-500 centrifugal chillers.

 Industrial Process Refrigeration: These include both packaged and built-up 

systems used in manufacturing processes as well as extra-large ice makers. High 

and low pressure systems are modeled as separate end uses, although the 

overwhelming majority of industrial process systems are high pressure units.

 Ice Skating Rinks: There are several different types of ice rink systems, but all are 

grouped into one end use in this analysis.

 Ice Makers: These include small, medium, and large ice makers used by a number 

of entities, including restaurants and hotels.

 Household and Light Commercial Air Conditioning: These include window units, 

unitary air conditioning systems, and heat pumps. All systems in this end use 

currently use HCFC-22.

 Refrigerated Appliances: These include household refrigerators and freezers, 

water coolers, vending machines, and dehumidifiers. Most currently use CFC-12 

as a refrigerant, but there are some CFC-502 units in existence.

 Refrigerated Transport Systems: These include systems designed to refrigerate 

materials in transit. They are found in trucks, trains, and ships.

 Mobile Air Conditioning: This end use includes systems installed in motor 

vehicles for the comfort of occupants.

Exhibits 4-1 and 4-2 display the consumption of ODSs in the refrigeration and air 

conditioning sectors as a fraction of total U.S. ODS consumption. The consumption amounts 
24

presented for ODSs in Exhibit 4-1 are weighted according to the chemicals' ozone depletion 

potentials (ODPs).6

 

 

6 Ozone depletion potential (ODP) is a relative index of the ability of a substance to cause ozone 

depletion. A reference level of 1.0 is assigned to CFC-11 and CFC-12. A given weight in the atmosphere 

of a chemical with an ODP of 0.5 would, in time, deplete half the ozone as the same weight of CFC-11 or 

CFC-12.


25

ex 4-1 & 4-2
26

4.3 CONTROL OPTIONS

The alternatives to CFC refrigerants with the widest applicability are HCFC and HFC 

refrigerants, although other alternatives such as ammonia, propane, and butane are possibilities in 

some end uses. Whether or not a chemical substitute is feasible in a given end use depends on a 

number of factors, including the required operating temperatures and pressures that need to be 

attained in that end use.

Substitutes can replace CFCs in both new and existing equipment in the refrigeration and 

air conditioning sector. In general, existing equipment will have to be modified C or retrofitted C

to be capable of using the substitutes. In this analysis, the effects of substitutes in new equipment 

were distinguished from the effects of the same substitutes as retrofits. This allows one to study

the implications of substitutes in new equipment and existing equipment independently from one 

another.

Additional information on possible substitutes, their availability, their potential end use 

market penetration, and their impact on energy consumption is presented in Section 4.6 with the 

results.

4.4 THE BASELINE FOR THE ANALYSIS

The baseline provides a benchmark against which the effects of possible substitution 

scenarios can be measured. An appropriate baseline incorporates assumptions regarding 

chemical emissions in the particular end use being examined, but at the same time it must account 

for all other sources of emissions of relevant compounds both in the U.S. and in the rest of the 

world (ROW). A global baseline is required because the incremental atmospheric effects of 

emissions in an end use depend on the quantity emitted from all other end uses worldwide.

The baseline is described in three steps. First, the uniform assumptions made throughout 

the analysis are specified. Second, the assumptions that are applied to all of the end uses 

(including end uses in other sectors such as solvents, fire extinguishing, foams, and sterilants) 

other than the one in which multiple substitutes are being compared are specified. Finally, the 

baseline assumptions used within an end use when evaluating multiple substitutes are specified.

4.4.1 Uniform Assumptions Made Throughout the Analysis

This section describes the uniform phaseout and recycling assumptions made throughout 

the analysis. The U.S. phaseout assumptions are listed in Exhibit 4-3. The exhibit lists the last 

year in which a given chemical can be produced for use in either new equipment or existing 

equipment. Other developed countries (Canada, Japan, Australia, New Zealand, and the nations 

of Western Europe) are assumed to follow the same schedule. The phaseout of ODSs in 

developing countries is assumed to lag that of the developed world by a decade. In addition, this 

analysis assumes that CFCs and HCFCs are recycled beginning in 1992 during the servicing and 

disposal of certain refrigeration equipment and that HFCs are likewise recycled starting in 1995. 

These recycling options are implemented in both the U.S. and the rest of the world (with a ten-year 

lag for developing countries).
27

EXHIBIT 4-3

PRODUCTION PHASEOUT ASSUMPTIONS FOR THE UNITED STATES

Chemical Compound

Phaseout Date

for New

Equipment

Phaseout Date

for Existing

Equipment

CFCs, methyl chloroform 

and carbon tetrachloride 1996 1996

halons 1994 1994

methyl bromide 2001 2001

HCFC-141b 2003 2003

HCFC-22 and HCFC-142b 2010 2020

All other HCFCs 2015 2030

4.4.2 Assumptions Made for All Other End Uses

This section summarizes the substances industry is assumed to choose to replace CFCs, 

halons and MCF in all end uses other than the one in which multiple substitutes are being 

compared. Although in a few sectors it remains uncertain which substitutes will be chosen, a 

"best estimate" substitute or combination of substitutes was assumed for each end use under the 

1996 phaseout in order to best approximate total worldwide emissions of Class I and Class II 

substitutes. These substitution scenarios were developed based on EPA's best judgment of the 

likely substitutes to be used in each end use under the 1996 phaseout.

4.4.3 Assumptions Made Within the End Use of Concern

This section describes the baseline assumptions used within the end use in which multiple 

substitutes are to be compared. In this analysis, two different baselines are used to present the 

results of the substitution scenarios. Before detailing these baselines, it is important to note that 

the choice of the baseline affects the presentation, and not the substance, of the results. Under 

either of the baselines described below, the relative differences between the substitutes with 

respect to ozone depletion will be the same. The absolute results presented for each substitute 

will, however, differ between the two baselines.

Each of the baselines used with the end use of concern are discussed below. One is a 

"no-risk baseline"; the other is a "no-substitution" baseline. These two baselines bound the range 

of health effects, since the first examines impacts from a risk-free scenario and the second presents 

effects assuming continued use of all CFCs.

4.4.3.1 Ideal Substitute Baseline
28

The "ideal" substitute is a hypothetical alternative that has an ozone depletion potential 

(ODP) of zero. The concept of the "ideal" substitute was developed to provide a "no-risk" point 

of reference from which actual alternatives could be compared against one another.

In this case, the difference between substitute and baseline scenarios isolates the effects of 

implementing the substitute in the U.S. relative to an ideal or "no-risk" substitute. As presented 

schematically in Exhibit 4-4, the reported effects of a substitute are the difference between the 

estimated effects of the substitution scenario and the "ideal" substitute baseline. The "ideal" 

substitute baseline consists of the "ideal" substitute in the end use of concern in the U.S. only and 

the "best estimate" substitute in all other end uses B both in the U.S. and in the rest of the world. 

The substitution scenario consists of the substitute in the end use of concern in the U.S., and the 

"best estimate" scenario in all other end uses. 

In the refrigeration and air conditioning sector, special care also has to be taken to 

distinguish between new and existing equipment, especially regarding baseline issues. As 

mentioned previously, this analysis examines separately the effects of substitutes in new 

equipment and in retrofits (existing equipment). As a result, for new equipment scenarios, the 

analysis measures the impact of replacing the ideal substitute with the substitution scenario. The 

retrofit scenarios assess the impact of replacing the ideal substitute in existing equipment with the 

substitution scenario.

EXHIBIT 4-4

SUMMARY OF METHODOLOGY USED IN ATMOSPHERICS RUNS

TO CALCULATE IMPACTS RELATIVE TO "IDEAL" BASELINE

United States Rest-of-World

End Use

of Concern

All Other

End Uses

End Use

of Concern

All Other

End Uses

BASELINE 

SCENARIO

"Ideal"

Substitute

Best

Estimate

Substitute

Best

Estimate

Substitute

Best

Estimate

Substitute

SUBSTITUTIO

N SCENARIO

Substitute

Best

Estimate

Substitute

Best

Estimate

Substitute

Best

Estimate

Substitute

The model includes consideration of speed of market penetration. In all analyses, the 

"ideal" substitute fully penetrates the new equipment market in 1992 and begins to penetrate the 

existing equipment market in 1992, reaching a maximum market penetration in 2000. The slower 

rate of penetration and the smaller final market share for retrofits reflects the behavior that would 

be expected in practice for most possible retrofit scenarios. As a result, a substitute that has low 

ODP but only penetrates that market slowly shows adverse health effects that are an artifact of the 

modeling, since until the time the substitute becomes available, Class I compounds must continue 

to be used.
29

The advantage of the "ideal" substitute baseline is that it allows for a "no-risk" point of 

reference for presentation purposes but accounts for changes in atmospheric conditions caused by 

activity in other end uses. It must be emphasized that the "ideal" substitute is only used as a 

reference point. In all end uses, the relevant comparisons are those between one substitute and 

another, not between the substitute and the ideal.

4.4.3.2 No Substitution Baseline

Under this baseline, the incremental performance of each substitute within an end-use is 

judged against a no substitution baseline (i.e., continued use of Class I substances within the end 

use). This option clearly indicates the reduction in ODP risks associated with replacing the use of 

Class I compounds with each of the potential substitutes and allows for direct comparisons in risk 

reduction achievable through each substitute.

In this case, the difference between substitute and baseline scenarios isolates the effects of 

implementing the substitute in the U.S. relative to a scenario that assumes the continued use of the 

Class I compound. As presented schematically in Exhibit 4-5, the reported effects of a substitute 

under this baseline are the difference between the estimated effects of the substitution scenario and 

the no substitution baseline. The no substitution baseline consists of the continued use of the 

Class I compound in the end use of concern in the U.S. only and the "best estimate" substitute in all 

other end uses B both in the U.S. and in the rest of the world. The substitution scenario consists of 

the substitute in the end use of concern in the U.S., and the "best estimate" scenario in all other end 

uses. 

EXHIBIT 4-5

SUMMARY OF METHODOLOGY USED IN ATMOSPHERICS RUNS

TO CALCULATE IMPACTS RELATIVE TO "NO SUBSTITUTION" BASELINE

United States Rest-of-World

End Use

of Concern

All Other

End Uses

End Use

of Concern

All Other

End Uses

BASELINE 

SCENARIO

Continued

CFC Use

Best

Estimate

Substitute

Best

Estimate

Substitute

Best

Estimate

Substitute

SUBSTITUTIO

N SCENARIO

Substitute

Best

Estimate

Substitute

Best

Estimate

Substitute

Best

Estimate

Substitute

As discussed above, this analysis examines separately the effects of substitutes in new 

equipment and in retrofits (existing equipment). As a result, for new equipment scenarios, the 

analysis measures the impact of phasing out the use of the Class I compound in new equipment in 

a given end use and replacing it with the substitution scenario. The retrofit scenarios assess the 

impact of replacing the use of the Class I compound in existing equipment in a given end use and 

replacing it with the substitution scenario.
30

The intent of the Agency in presenting the resulting of the tradeoff analysis relative to the 

no substitution baseline is to indicate that all of the substitutes analyzed are substantially less 

harmful to the ozone layer than continued use of CFCs. In presenting the results in this fashion, 

however, EPA is cognizant of the fact that the reduction in ODP risks due to the phaseout of Class 

I compounds are attributable to the Class I Phaseout Rule and not the Safe Alternatives Program.

4.5 OVERVIEW OF THE MODELING APPROACH

This section provides a brief description of the Atmospheric and Health Effects 

Framework (AHEF), the modeling framework used to assess the global environmental impacts of 

alternatives to Class I substances in the United States.

4.5.1 Chemical Use

The starting point of an AHEF analysis is to forecast the consumption of the relevant 

chemical compounds in each of the end uses in each sector. For U.S. estimates, this task is 

usually performed by the Vintaging Model, which simulates the chemical requirements of the 

various equipment types in each end use over their lifetimes.7 The Vintaging Model has been 

used to support several significant Agency rulemakings including the phaseout of Class I and II 

compounds under Section 604 of the Clean Air Act. It is documented in Appendix A of EPA's 

Regulatory Impact Analysis: Compliance with Section 604 of the Clean Air Act for the Phaseout of 

Ozone Depleting Substances (EPA 1992), which was included in the Phaseout rulemaking docket 

and was subject to public review and comment.

For other regions of the world, chemical use estimates are typically derived by applying the 

London Amendment reduction schedule to estimates of what demand would be in the rest of the 

world had this phaseout never occurred.

4.5.2 Chemical Emissions

Emissions of a compound into the atmosphere are not necessarily simultaneous with use. 

The delay between use and emission of a compound depends on the kind of equipment in which 

the compound is employed. For example, hermetically sealed refrigerators emit CFCs over a 

very long period of time, whereas packaging foams emit similar compounds in less than one year. 

AHEF simulates compound emissions by means of release functions which specify the time delay 

between use and emissions for each particular end use.

 

 

7 The data contained in the Vintaging Model were obtained through a series of meetings held by EPA 

with representatives of the air conditioning and refrigeration industries during the Spring and Summer of 

1991. Questionnaires developed at the meetings were analyzed and the information contained reduced to 

input files in a form usable by the model. Additional information was obtained from trade associations, 

professional societies, equipment manufacturers, and from the literature.
31

4.5.3 Atmospheric Effects

The output from the emissions module are used in an atmospheric model, the Atmospheric 

Stabilization Framework (ASF), that predicts changes in stratospheric ozone associated with 

changes in atmospheric composition. ASF computes the globally and annually averaged 

concentrations of climatically important atmospheric constituents, taking into account various 

feedbacks between climate parameters and the constituents themselves. Examples of feedbacks 

accounted for in ASF are:

 The dependence of a compound's atmospheric lifetime on column (stratospheric) 

ozone and temperature;

 Radiative and chemical feedbacks due to water vapor;

 Ocean absorption;

 Atmospheric circulation effects; and

 Chemical interactions between compounds.

ASF relies on simple empirical relations based either on observations or on the results of 

more complex models in order to quantify physical feedbacks. In particular, the dependence of 

model ozone on stratospheric chlorine is adjusted so that it predicts a historical ozone depletion 

equal to that observed for the current atmosphere. In addition, ASF input parameters are adjusted 

to give column ozone changes that are consistent with consensus ODP estimates.

The ASF is a "consensus" model developed by a committee of prominent atmospheric 

scientists in government, academia, and private consulting firms. It was designed to approximate 

the behavior of more sophisticated two and three-dimensional physical models without requiring 

the computing power needed for physical simulations. Additional information on the ASF can be 

found in National Aeronautics and Space Administration Conference Publication 3023, An 

Assessment Model for Atmospheric Composition (NASA 1988).

4.5.4 Human Health Effects

The ozone column changes predicted by the ASF are inputs to a health effects model that 

estimates the number of skin cancer cases and fatalities that result from the scenario modeled. 

Estimates of skin cancers include both melanoma and non-melanoma cancers and represent all 

cases experienced by individuals born in the United States before 2030.

In order to quantify the human health impacts of ozone depletion in the U.S., the globally 

averaged ozone depletion predicted by ASF is converted to estimates of depletion by latitude. 

This latitudinal variation is estimated using simple regression techniques from a prior 

two-dimensional modeling study. (Isaksen, 1986). Results from a separate UV model are in turn 

used to estimate changes in UV-B intensity associated with the latitudinally-varying ozone 

depletion. 

Human health effects are computed by AHEF as a function of UV-B exposure. The 

effective exposure of various population cohorts, representing different sexes and age groups, is 

estimated using appropriate factors that weight exposure at various stages during a person's 
32

lifetime. Empirical "dose-response" relationships for each cohort are then used to predict 

changes in skin cancer and cataract incidence over time.

The human health effects model was reviewed in 1987 as part of an EPA Science Advisory

Board review of Assessing the Risks of Trace Gases that Can Modify the Stratosphere (EPA, 

1987).

4.6 MODEL RESULTS

This section presents the results of the analysis and lists several considerations that are 

helpful in interpreting them.

4.6.1 Description of Results

The results are presented in Exhibits 4-6 through 4-45, one for each end use sector. Each 

exhibit contains two tables and two graphs. Parts A and B of each exhibit present the atmospheric 

results relative to the "ideal" baseline. Parts C and D of each exhibit present the results relative to 

the no substitution baseline. The table lists the assumptions regarding the availability and 

replacement potential of each alternative and estimated atmospheric and health effects resulting 

from those assumptions. Note that numbers in parenthesis represent decreases from the baseline 

(e.g., negative numbers). The graph illustrates the change in cumulative Clx in 2075 for each of 

the alternatives.

More specifically, the following information is provided:

Start Date: The year in which the alternative option is expected to be commercially available 

(i.e., after all research and development is complete). A start date of 1992 indicates that the 

alternative is currently available.

Years to Maximum Market Penetration: The number of years it would take for an alternative, 

once it became commercially available, to reach its maximum possible use in the end use market.

Maximum Market Penetration: The maximum, technically feasible percentage of total ODS 

consumption in an end use that can be replaced by the alternative.

Cumulative Clx: This is a measure of the change in the total quantity of chlorine in the 

stratosphere over time. More technically, it is the integral of the Clx curve above two parts per 

billion.

Skin Cancer Cases: The estimated change in the number of cases of melanoma and 

non-melanoma skin cancers experienced by individuals in the U.S. population born before 2030. 

The estimate of skin cancers includes fatalities that may result from these cancers.

Skin Cancer Fatalities: The estimated change in the number of fatalities due to melanoma and 

non-melanoma skin cancers of individuals in the U.S. population born before 2030. Skin cancer 

fatalities are a small portion of the total number of skin cancer cases.

4.6.2 Interpreting the Results
33

When interpreting the results, one should be aware of the following:

 For the results presented relative to the ideal baseline, the baseline for the 

substitution scenarios for new and existing equipment assumes that the "ideal" 

substitute is fully implemented in new equipment in 1992 and is retrofit in 50% of 

existing equipment between 1992 and 2000. As a result, the numbers presented 

for each alternative in new equipment scenarios account for: (1) the effects of that 

alternative; (2) the effects of any continued CFC use occurring in the period after 

the implementation of the ideal substitute in the baseline and before the 

implementation of the alternative; and (3) the continued CFC use attributable to the 

lack of a retrofit. Accordingly, the later the availability of the alternative, the 

greater the quantity of continued CFC use that is attributed to that alternative. 

Even an ozone-safe alternative can have cancers indirectly attributed to it if it 

penetrates the market after the "ideal" substitute.

 Under the ideal baseline, a "no retrofit" scenario (i.e. "ideal" in new equipment and 

continued CFC use in existing equipment) is included with the retrofit results for 

each end use to indicate the effects of continued CFC use in existing equipment that 

are potentially avoidable through retrofitting. The results of this scenario are 

helpful in interpreting both retrofit and non-retrofit graphs because they

demonstrate the benefits of retrofitting and show how much of the effects in new 

equipment scenarios can be attributed to the lack of a retrofit.

 Since different HCFCs have different phaseout dates, the total quantity of 

substitute chemical ultimately released into the atmosphere may differ depending

on the alternative. For example, the results of scenarios using HCFCs with early 

phaseout dates reflect the fact that less of the chemical is ultimately used.

 Blends containing HCFCs are phased out as soon as their earliest constituents are 

phased out.

 Modeling reflects the market penetration potential for each substitute. This means 

that health effects are dependent on potential market size, so that a low 

ozone-depleting substitute with large market potential could look worse than a high 

ozone-depleting substitute with only small uses.


34

Exhibits 4-6 through 4-45.

80 pages

92

4.7. Global Warming 

There is no doubt that human activity is increasing the concentration of greenhouse gases 

in the atmosphere. The sources and industrial sectors contributing these gases are extremely 

varied. No single economic sector can be held entirely responsible for the greenhouse effect, nor 

can a single source, because it contributes only a small amount to the problem, be exempt from 

accountability. Additional research is needed to better characterize the effects of greenhouse gas 

emissions on the environment and to evaluate the benefit of various reduction strategies. 

However, as in the case of ozone depletion, there is growing international consensus among 

scientists and policymakers that immediate efforts are necessary to curb the rate of growth of 

atmospheric concentrations of these gases.

Based on total emissions, the major greenhouse gases are carbon dioxide (CO2) and 

methane (CH4), and it is on these major contributors that EPA has focused much of the effort of its 

nascent voluntary programs such as Green Lights. However, a substantial contribution is made in 

the aggregate by other gases including CFCs, halons, and other halocarbons. These minor or 

trace gases are important for two reasons. First, although these gases are currently emitted in 

smaller quantities than CO2 and CH4, their effectiveness in influencing climate tends to be greater. 

Second, while individual use of these gases may add little to the overall burden, the rising 

concentration of greenhouse gases in the atmosphere cannot be controlled without addressing the 

aggregate effect of the trace gases.

As the transition away from the ozone-depleting compounds proceeds, a key policy goal of 

the SNAP program in reducing overall risk is to be sure that this shift does not also result in a 

significant rise in contributions to global warming due to an increased reliance on greenhouse gas 

substitutes. Alternatives reviewed under SNAP to date have varying potential to contribute to 

global warming. Their contribution depends on many factors evaluated under SNAP, including 

radiative properties and persistence in the atmosphere. It is difficult to make relative judgements 

among those which do contribute to global warming, however, because their contributions, when 

viewed through the SNAP lens of individual end-uses, are uniformly small.

Recognizing this, SNAP avoids evaluating the viability of greenhouse gases as substitutes 

based solely on a single measure, such as an end-use by end-use contribution to actual warming. 

Instead, a broader evaluation of a substitute's inherent characteristics, such as its absorption spectra 

and atmospheric lifetime, is used to help clarify whether a substitute could contribute significantly 

to the problem relative to other substitutes available. For example, a compound which might be 

acceptable in its contribution to global warming in limited uses might become a problem in 

widespread emissive uses. Thus, a careful review of the volume likely to be used in a particular 

end-use, and how much is likely to be emitted from that end-use, also helps. Finally, because 

SNAP's primary goal is to facilitate the transition away from the ozone-depleting chemicals, a 

substitute which is also a significant global warming gas might be allowed with controls if there 

exist few other alternatives in a particular end-use.

This section reviews the risk screen for global warming under SNAP. It includes a 

discussion of the nature of the global warming problem, general properties of greenhouse gases, 

and global warming resulting from changes in the energy efficiency of equipment or processes 

using the alternative chemicals.
93

4.7.1 The Nature of the Global Warming Problem

The Earth's stable average temperature is maintained by a radiative balance in which the 

amount of energy absorbed from the sun is equal to the amount of energy radiated back into space 

by the Earth and atmosphere. If a factor is introduced into the atmosphere that changes this 

balance, the climate must warm or cool until the radiative fluxes are equal and the balance is 

restored. A change of this kind is known as a change in radiative forcing (or warming 

commitment). Radiative forcing, expressed in watts per square meter (W/m2), is a measure of the 

downward radiation flux received by the climate system. Concerns about global warming stem 

from observed increases in the concentrations of certain gases that may be able to alter the climate 

by causing an increase in radiative forcing.

A characteristic that these gases share is that they absorb radiation in the infrared (or 

thermal) part of the electromagnetic spectrum. Most of the energy that the Earth receives from 

the sun is in the form of shortwave radiation in the visible and ultraviolet parts of the spectrum. 

The energy emitted from the Earth to space is in the form of longwave radiation in the infrared part 

of the spectrum. These gases absorb some of the outgoing infrared (or thermal) radiation and 

re-emit it both up into space and back down to the Earth. The net result is a decrease in the heat 

radiation escaping to space and an increase in the heat radiation falling to the Earth (an increase in 

radiative forcing). Because this process tends to concentrate heat in the troposphere, it is known 

as the greenhouse effect. The gases responsible for the greenhouse effect are known as 

greenhouse gases. Greenhouse gases include carbon dioxide, methane, and nitrous oxide, as well 

as chlorofluorocarbons (CFCs) and some CFC substitutes.

The greenhouse effect is a natural phenomenon which plays an important role in keeping 

the Earth warm. Concerns about the greenhouse effect and global warming arise from indications 

that human activities have been increasing the concentrations of both naturally occurring and 

anthropogenic greenhouse gases. Increasing concentrations of these gases may lead to an 

enhanced greenhouse effect, which may cause the Earth to warm at a rate much faster than natural 

rates of climate change. This accelerated climate change may have a number of adverse 

consequences including damage to ecosystems, changes in climatic zones, changes in weather 

patterns, and sea level rise. Adjusting to these changes quickly may be both difficult and 

expensive.

4.7.2 Properties of Greenhouse Gases

All organic compounds that can volatilize into the atmosphere share the property that they 

absorb energy in the infrared portion of the electromagnetic spectrum. However, these gases do 

not all absorb infrared radiation equally well, and thus some have greater impacts than others on 

global warming. The following factors determine the global warming impact of emissions of a 

particular gas:

 Atmospheric lifetime. Various physical and chemical processes tend to remove 

and break down chemicals in the atmosphere. Atmospheric lifetime is a measure 
94

of how long a gas stays in the atmosphere before it is removed by these processes.8 

The lifetimes of the greenhouse gases are determined by their sources and sinks in 

the oceans, atmosphere, and biosphere. In general, the most effective greenhouse 

gases are those with long lifetimes since the impact of long-lived gases is more 

persistent than the impact of short-lived gases. In some cases this persistence may 

be cause for concern. With very-long-lived gases it may take thousands of years 

for concentrations to decline significantly after emissions have stopped. Thus, the 

impacts these emissions have are essentially irreversible.

 Molecular weight. Emissions are typically measured according to their mass (in 

kilograms). However, the increase in atmospheric concentration (by volume) 

resulting from an emission is proportional to the number of molecules in the 

emission, not the total mass of the emission. The number of molecules in an 

emission of a given mass is inversely proportional to the molecular weight of the 

gas emitted. As a result, the molecular weight is needed to determine the increase 

in concentration resulting from an emission of a given mass. The lower the 

molecular weight of the gas, the greater the increase in concentration resulting from 

a given emission.

 Radiative forcing per molecule. This is a measure of the effectiveness of the gas at 

absorbing infrared radiation emitted by the Earth. It is proportional to the increase 

in radiative forcing resulting from a given increase in concentration.

Of these factors, only molecular weight is an irreducible characteristic of a gas. 

Atmospheric lifetime depends on other characteristics such as solubility in water, rates of reaction 

with other components of the atmosphere, and susceptibility to photolysis. Radiative forcing per 

molecule depends on a number of characteristics that are relevant to greenhouse gas behavior. 

These include the following:

 Integrated infrared band strength. Each kind of molecule absorbs energy at a 

unique set of wavelengths. The wavelengths at which a molecule absorbs energy

are in patterns of contiguous regions in the electromagnetic spectrum which are 

referred to as absorption bands. A molecule's absorption bands together make up 

its absorption spectrum. The strength of the gas's infrared absorption spectrum is a 

measure of how well molecules of the gas absorb radiation at their characteristic 

wavelengths (i.e., the stronger the absorption band, the more energy that is 

absorbed by the molecule).

 

 

8

 Atmospheric lifetimes are commonly modeled as e-folding lifetimes. This means that the 

concentration of a gas is assumed to decay exponentially. Concentration through time is given by the 

following equation:

Ct=C0e

-

t

L

where Ctis the concentration at time t, C0 is the initial concentration, and L is the atmospheric life of the 

gas. If the initial concentration of a gas is 1 ppb, its concentration after one lifetime is 1/e (about 0.37) ppb. 

After two lifetimes the concentration is 1/e2(about 0.14) ppb. In theory this means that the concentration 

is never truly zero. However, after a few lifetimes it does become vanishingly small.
95

 Location of infrared absorption bands. The location of the gas's infrared 

absorption bands is important for two reasons: First, the energy radiated from the 

earth is not evenly distributed across the infrared spectrum. More energy is 

radiated at some wavelengths than at others. Molecules with absorption bands at 

wavelengths of high infrared radiation will tend to be more effective greenhouse 

gases than molecules with absorption bands at wavelengths of low infrared 

radiation. Second, the impact of a greenhouse gas may be reduced if its absorption 

bands overlap with those of other gases present in the atmosphere in significant 

quantities. For example, if a gas has absorption bands that overlap with those of 

an abundant greenhouse gas like carbon dioxide, the relative impact of the gas on 

radiative forcing is reduced since much of the energy at these wavelengths is 

already absorbed.

 Initial concentration of the gas. If the initial atmospheric concentration of a gas is 

high enough so that a significant portion of the energy at relevant wavelengths is 

already absorbed, the impact of additional increases in concentration is reduced. 

This effect is significant for carbon dioxide. It is not significant for CFCs and 

CFC substitutes since they are present in much smaller quantities than carbon 

dioxide. Radiative forcing scales linearly with concentration for these chemicals.

A useful index for comparing emissions that incorporates all of these factors is the Global 

Warming Potential (GWP). The GWP depends on the position and strength of the absorption 

bands of the gas, its lifetime in the atmosphere, its molecular weight, and the time period over 

which the climate effects are of concern. Specifically, the GWP is defined as the time-integrated 

change in radiative forcing resulting from a kilogram of emissions of a given chemical relative to 

the time-integrated change in radiative forcing resulting from a kilogram of emissions of a 

reference gas, typically carbon dioxide.9

Because different gases have different lifetimes, the period of integration has an important 

impact on relative GWPs. This point is illustrated by the example of two different gases, each 

with an initial concentration of 1 ppb. If the lifetime of the first gas is 10 years, its concentration 

will be 1/e10 (0.00005) ppb after 100 years (ten lifetimes). A 100-year GWP captures the entire 

impact of this gas since the concentration of the gas is effectively zero at the end of the period of 

integration, and it can no longer influence radiative forcing. If the lifetime of the second gas is 

100 years, its concentration will be 1/e (about 0.37) ppb after 100 years (one lifetime). A

100-year GWP does not capture the entire impact of this gas since the gas is still present in 

significant quantities at the end of the period of integration, and it still affects radiative forcing. If 

the period of integration were lengthened, the ratio of GWPs between the long-lived and the 

short-lived gases would increase because the value of the integral in the numerator would increase, 

while the value of the integral in the denominator would remain the same.

 

 

9

 Climate Change: The IPCC Scientific Assessment. Intergovernmental Panel on Climate Change. 

1990.
96

4.7.3 Properties of ODSs and ODS Substitutes

Exhibit 4-46 presents atmospheric lifetime, molecular weight, integrated infrared band 

strength and GWPs for a number of ODSs and ODS substitutes. Although there is overlap 

between categories, in general the PFCs have the highest GWPs among ODS substitutes. HFCs 

are next, followed by HCFCs, which have the lowest GWPs. PFCs have high GWPs because of 

their high integrated band strengths and their extremely long atmospheric lifetimes. HCFCs 

generally have low GWPs because of their short atmospheric lifetimes (see Exhibit 4-46). HFCs 

typically fall in the middle because of strong integrated band strengths and moderate atmospheric 

lifetimes. In examining this table the following issues should be considered:

 Although the GWPs of ODSs and ODS substitutes may be thousands of times the 

GWP of the reference gas, carbon dioxide, this is offset by the fact that emissions of 

these compounds are orders of magnitude smaller than emissions of carbon 

dioxide. Nevertheless, it is estimated that CFCs accounted for about 23 percent of 

the direct radiative forcing from US emissions of greenhouse gases in 1990.10

 If the lifetime of a chemical is short compared to the lifetime of the reference gas, 

the GWP of the chemical declines as the period of integration increases. If the 

lifetime of the chemical is long compared to the lifetime of the reference gas, the 

GWP of the chemical rises as the period of integration increases.11

 

 

10

 This estimate does not account for the indirect atmospheric effect of CFC emissions on radiative 

forcing. CFCs play a role in the depletion of stratospheric ozone, which is itself a radiatively active gas. 

Ozone depletion may reduce the net increase in radiative forcing that would otherwise occur as a result of 

CFC emissions. This indirect effect does not apply to HFC and PFC emissions, which are not ozone 

depleting.

 

11

 Because carbon dioxide is removed from the atmosphere through complex processes that cannot be 

modeled as simple exponential decay, this relationship is not always monotonic.
97

 In practice a high GWP does not necessarily mean a large impact on warming. If 

chemicals are never emitted they cannot cause a direct contribution to global 

warming even if they have high GWPs. For example, if good service practices are 

in place, emissions from hermetically sealed household refrigerators are very small. 

If the material is recovered for recycling or destruction after the useful life of the 

equipment, the refrigerant is never released to affect the atmosphere. In contrast, 

mobile air conditioners tend to be leaky. Substitutes used in this end use are more 

likely to be released to the atmosphere and, thus, impact global warming.
98
99

4.7.4 Indirect Effects from Changes in Energy Efficiency

In addition to direct and indirect atmospheric effects, ODS substitutes may also have 

indirect energy effects that can influence global warming. Use of alternative chemicals may

change the energy efficiency of equipment and products currently using CFCs. Because most 

energy is derived from burning fossil fuels, changes in energy efficiency may result in changes in 

carbon dioxide, nitrous oxide, and methane emissions, which will impact radiative forcing and 

global warming. The two major end use categories in which the use of alternatives can impact the 

energy efficiency of equipment or products are refrigeration and air conditioning applications and 

foam insulation applications. The key factors affecting energy efficiency for each of these 

applications are discussed below.

4.7.4.1 Refrigeration and Air Conditioning End Uses

Refrigeration and air conditioning equipment can consume significant quantities of energy 

during normal operation. Whether used in new or existing equipment, a new refrigerant can 

impact both the energy efficiency and cooling capacity of the refrigeration system. The specific 

factors that impact the potential change in energy consumption associated with the use of a new 

refrigerant are as follows:

 Thermodynamic Properties of the Alternative Refrigerant: The thermodynamic 

properties of the refrigerant affect the amount of energy used by the compressor.12 

This is because these properties determine the evaporating and condensing 

pressures at which the equipment can operate given the temperature requirements 

of the application. In practice, the greater the pressure difference between the 

evaporator and the condenser, the more the compressor must work to achieve a 

given cooling capacity.

 Design of Equipment Components: New refrigeration equipment is always 

designed around the refrigerant to be used. System components such as the 

condenser, evaporator, or other heat exchangers are selected to minimize the work 

that a refrigeration system needs to do given a particular refrigerant. For example, 

switching from a CFC to an alternative refrigerant might require a different type of 

heat exchanger tubing in the evaporator to enhance heat transfer or different sized 

expansion devices to better control the amount of refrigerant metered to the 

evaporator.

 Retrofit Optimization: The use of an alternative refrigerant in existing equipment 

(retrofits) often results in a decrease in the energy efficiency or refrigerating 

capacity of the equipment. This is because the equipment was originally designed 

to operate most efficiently given the thermodynamic properties of the CFC 

refrigerant. A number of steps can be taken to alter existing equipment so that it 

operates more efficiently with a given alternative. Such steps include changing 

 

 

12

 Components in heating, ventilation, and air conditioning systems that consume energy include 

fans, pumps, defrost heaters, and compressors. In terms of energy use the component most significantly 

affected by the refrigerant used is the compressor.
100

the motor drive train, increasing the motor speed, changing the heat exchangers, 

and replacing the impeller (for chillers). The gains in energy efficiency associated 

with such measures must be weighed against cost and possible impact on 

refrigeration capacity.

A widely used measure for the energy efficiency of refrigeration equipment is the 

coefficient of performance (COP). This is defined as the total amount of refrigeration delivered 

by the equipment divided by the total amount of energy (i.e., work) input into the system. The 

COP can be calculated for an ideal cycle. The COP for an actual piece of equipment can be 

measured through field testing of the actual energy input and refrigerating effect of the equipment. 

Field measurements of COP may vary from the ideal COP because of energy losses not accounted 

for in the model, or variations from the ideal cycle caused by friction losses or pressure drops.

Finally, it is important to note that actual changes in energy efficiency are equipment and 

application specific. As a result, it can be difficult to generalize about the potential impacts of a 

given substitute on energy efficiency in a given refrigeration or air conditioning application.

4.7.4.2 Foam Insulation

Several factors combine to limit heat flow in thermal insulating foams including the 

volume fraction of the solid phase; the cell size which suppresses convection and radiation through 

cell walls; and the conductivity of the enclosed cell gases. In addition to the conductivity per unit 

volume of the foam, the foam thickness also affects the thermal insulating capacity of foam 

products.

CFCs were highly suitable as blowing agents in part because their low thermal 

conductivity contributed to the insulating capacity of the foam product. Substitute blowing 

agents with higher thermal conductivity contribute less. Higher thermal conductivity of the 

substitute blowing agent, however, does not necessarily translate into lower energy efficiency in 

foam products if formulation or thickness changes are made to compensate for the relative change 

in substitute blowing agents.
101

CHAPTER 4 REFERENCES

Isaksen, I.S.A. 1986. Ozone Perturbation Studies in a Two Dimensional Model with 

Temperature Feedbacks in the Stratosphere Included. Presented at the UNEP 

Workshop on the Control of Chlorofluorocarbons, Leesburg, Virginia. September 

1986.

National Aeronautics and Space Administration (NASA). 1989. An Assessment Model for 

Atmospheric Composition. National Aeronautics and Space Administration 

Conference Publication 3023.

U.S. EPA. 1992. Regulatory Impact Analysis: Compliance with Section 604 of the Clean Air 

Act for the Phaseout of Ozone Depleting Substances, Appendix A. Office of Air and 

Radiation. March 12, 1992.

U.S. EPA. 1987. Assessing the Risks of Trace Gases that Can Modify the Stratosphere. Office 

of Air and Radiation. December 1987.
5. OCCUPATIONAL EXPOSURE AND HAZARD ANALYSIS13

5.1 INTRODUCTION

This section presents an analysis of potential occupational exposures to alternative 

refrigerant materials during the manufacture, installation, repair, and disposal of refrigeration 

equipment in several end-use sectors. Evaluation of potential occupational exposures to these 

materials was based primarily on the use of a modelling approach that is similar to the approach 

used by EPA in their previous analyses of potential occupational exposure to refrigerant vapors 

(EPA 1990). Where possible, the results obtained from the model were compared to available 

worker exposure data to determine the direction and magnitude of any uncertainty resulting from 

assumptions used in the model. The following discussion describes the model used to evaluate 

potential occupational exposures to alternative refrigerants; this is followed by a discussion of the 

results obtained.

5.2 DESCRIPTION OF THE MODEL

Occupational exposure to a gas or vapor is the result of two events: a release of the 

material to the air and the presence of a worker within the contaminated space. The duration and 

magnitude of the resulting exposure is influenced by (1) the duration and intensity of the release, 

(2) the rate at which contaminated air is diluted with uncontaminated air in the space affected by 

the release, (3) the proximity of the worker to the source of the release, and (4) the length of time 

that the worker remains in the space affected by the release.

The first two factors are addressed directly by the mathematics of the "box" model used in 

this analysis. This model has been widely used for many years to estimate probable exposures of 

workers to hazardous airborne materials, and has been described in detail by the National Institute 

for Occupational Safety and Health (NIOSH 1973). Starting with a fundamental material 

balance, assuming that contaminated air is diluted with uncontaminated air:

Rate of Accumulation = Rate of Generation - Rate of Removal 

Where: 

C = Concentration of gas or vapor at time t

G = Rate of generation of the contaminant (cubic feet per minute (cfm))

Q'= Effective rate of ventilation that is 

 corrected for incomplete mixing (cfm)

V = Volume of room or enclosure (ft3)

Converting units and rearranging the equation yields the mass balance equation

 

 

13 This analysis was prepared by an industrial hygienist certified by the American Board of 

Industrial Hygiene. 
Where:

V = Room Volume (m

Ci = Indoor Concentration (g/m

S = Source Generation Rate (g/hr)

rt = Residence Time of the indoor air (hr)

m = Mixing Factor (dimensionless)

Co = Outdoor Concentration (g/m

The integrated form of this equation can be used to calculate the average concentration of a 

contaminant in a room during the release of a chemical substance:

Where:

Cb = Concentration already existing in the room when 

the emission starts (i.e., at time = 0)

Assuming that the concentration of contaminant at time = 0 is zero (i.e., C

contaminated air is diluted with uncontaminated air (i.e., C

reached a steady-state (equilibrium) level, the integrated equation above can be further simplified: 

A dimension analysis reveals that:

Since it is customary to measure occupational exposures to gasses and vapors in units of 

parts per million, the equation above can be modified to:

where MW is the molecular weight of the contaminant.

V = Room Volume (m3)

= Indoor Concentration (g/m3)

Source Generation Rate (g/hr)

= Residence Time of the indoor air (hr)

m = Mixing Factor (dimensionless)

= Outdoor Concentration (g/m3)

The integrated form of this equation can be used to calculate the average concentration of a 

room during the release of a chemical substance:

= Concentration already existing in the room when 

the emission starts (i.e., at time = 0)

Assuming that the concentration of contaminant at time = 0 is zero (i.e., C

ontaminated air is diluted with uncontaminated air (i.e., Co = 0), and that the concentration has 

state (equilibrium) level, the integrated equation above can be further simplified: 

A dimension analysis reveals that:

Since it is customary to measure occupational exposures to gasses and vapors in units of 

parts per million, the equation above can be modified to:

is the molecular weight of the contaminant.

The integrated form of this equation can be used to calculate the average concentration of a 

Assuming that the concentration of contaminant at time = 0 is zero (i.e., Cb = 0), that 

= 0), and that the concentration has 

state (equilibrium) level, the integrated equation above can be further simplified: 

Since it is customary to measure occupational exposures to gasses and vapors in units of 
Because the residence time 

(ACH), the following can be derived, which is the working equation used to estimate worker 

exposure to alternative refrigerants: 

104

Because the residence time r is the inverse of the air exchange rate in air changes per hour 

(ACH), the following can be derived, which is the working equation used to estimate worker 

exposure to alternative refrigerants: 
105

However, as described above, the degree to which a worker is exposed to a gas or vapor 

also depends on the location of the worker at the time the contaminant is released. To address this 

aspect, the use of the box model was modified to recognize the fact that workers move around an 

area where a release occurs. Specifically, the workspace was divided into four areas or zones. 

These zones are defined as follows:

 Zone 1 represents a space measuring 3' x 3' x 3' centered around an emission 

source. A worker is said to be in Zone 1 whenever his/her breathing zone is within 

18 inches of the emission source. Thus, this zone represents an area occupied by a

worker performing operations within an arm's reach of the emission source;

 Zone 2 represents a space measuring 12' x 12' x 12' centered around an emission 

source. A worker is said to be in Zone 2 while working within 6 feet of the source;

 Zone 3 represents a space measuring 30' x 30' x 30' centered around an emission 

source. A worker is considered to be in Zone 3 while working within 15 feet of the 

emission source; and

 Zone 4 represents a space sufficiently far from the emission source that no 

measurable exposure occurs.

Thus, refrigerant vapor concentrations will be highest in Zone 1 and will decrease as the worker 

moves through each zone away from the emission source. Use of this approach captures the idea 

that there is a vapor concentration gradient surrounding the emission source, and that a worker, in 

the course of performing normal work duties, will move between these zones.

A second important assumption concerns the rate at which air is exchanged within each 

zone. In the implementation of the box model, air within a small space is exchanged at a faster 

rate than is air within a larger space. This is due to the presence of local air currents and eddies. 

In Zone 1, which is the smallest space defined in the model, the motion of the worker's hands and 

tools will serve to increase the rate of air exchange; however, in a larger space, local air currents 

will have a lesser effect on the overall rate of air exchange within that space. As such, the air 

within a 3' x 3' x 3' space may be exchanging with surrounding air at a rate of 30 air changes per 

hour (ACH) even though the overall rate of air exchange within a 30' x 30' x 30' room is only 0.5 

ACH. In the model, it is assumed that air within Zone 1 is moving through the zone at a rate of 

about 2 mph. This rate is cut in half for Zone 2, and by 75 percent in Zone 3. The rate of air 

movement within Zone 3 is equivalent to about 50 feet per minute, which represents a background 

rate of air movement frequently seen in industrial facilities having moderate general dilution 

ventilation. A mixing factor of 0.5 is assumed, which cuts the effective air exchange rate in half.

Thus, to implement the box model, the variables in the working equation above were 

substituted as follows. The variable S is the release rate in g/hr. The value of S was derived from 

the Vintaging model used to estimate refrigerant release rates for various release scenarios. The 

release rate per event (from the Vintaging model) was multiplied by the number of events 

estimated to occur over a workday. For equipment manufacturing, the number of events per 

workday was assumed to equal the number of units produced per plant per year divided by 365 

days per year. For scenarios where fewer than 365 units are manufactured per year, it is assumed 

that the event causing the emission occurs over a single 8-hour workday, rather than over several 

days. For installation and repair operations, it is assumed that one event occurs per workday for 

large refrigeration systems and four events per workday for small systems. For disposal 
operations involving refrigerators and freezers, other refrigeration appliances, and mobile air 

conditioners, it is assumed that 100 units are disposed of over an 8

end-use sectors, it is assumed that one unit is disposed of during a single shift.

The variable V represents the volume of space in which the worker is performing his or her 

work duties. For each exposure scenario, it is assumed that a worker spends a certain p

of time within each of the four zones, as follows. For manufacturing and installation operations, 

it is assumed that a worker spends 10

50 percent in Zone 2, 30 percent in Zone 3, and 

assumed that a worker spends 20 percent of the workday in Zone 1, 40 percent in Zone 2, 20 

percent in Zone 3, and 20 percent in Zone 4; this reflects the likely possibility that, in repair 

operations as compared to manufacturing or installation operations, a worker will spend a larger 

proportion of the workday in close proximity to the emission source, but will also spend a greater 

proportion of the day away from the emission source while travelling to the

After using the box model to estimate the average vapor concentration within each zone, a 

worker's 8-hour time-weighted-average exposure is calculated as follows:

where 

Cx = Concentration of vapor within Zone x; and

Px = Percent of time spent in Zone x by the worker.

The term representing Zone 4 drops out because there is no exposure to refrigerant vapors in Zone 

4 (by definition).

To estimate short-term (i.e., 30

it is assumed that 25 percent of the daily emission is released over a 30

5.3 DISCUSSION OF RESULTS

5.3.1 Presentation of Results

The attached tables (Attachment 5

work operation, and alternative refrigerant. For each scenario, the tables report the average 

8-hour and 30-minute time-weighted average (TWA) concentrations of refrigerant present in each 

of the zones, and the estimated 8

exposed.

Exhibit 5-1 summarizes the occupational exposure limits for the alternative refrigerants 

that were used to determine whether workers may be exposed to potentially hazardous airborne 

gas or vapor concentrations. Exhibit 5

model suggests that worker exposures may exceed either the 8

exposure limit for the alternative refrigerant. The highest exposures are predicted to occur during 

the manufacturing and disposing of industrial process (high pressure build

systems.

5.3.2 Interpretation and Comparison of Model Results with Sampling Data

106

operations involving refrigerators and freezers, other refrigeration appliances, and mobile air 

conditioners, it is assumed that 100 units are disposed of over an 8-hour shift. For all other 

, it is assumed that one unit is disposed of during a single shift.

represents the volume of space in which the worker is performing his or her 

work duties. For each exposure scenario, it is assumed that a worker spends a certain p

of time within each of the four zones, as follows. For manufacturing and installation operations, 

it is assumed that a worker spends 10 percent of his or her time over an 8-hour workday in Zone 1, 

50 percent in Zone 2, 30 percent in Zone 3, and 10 percent in Zone 4. For repair operations, it is 

assumed that a worker spends 20 percent of the workday in Zone 1, 40 percent in Zone 2, 20 

percent in Zone 3, and 20 percent in Zone 4; this reflects the likely possibility that, in repair 

ompared to manufacturing or installation operations, a worker will spend a larger 

proportion of the workday in close proximity to the emission source, but will also spend a greater 

proportion of the day away from the emission source while travelling to the repair site.

After using the box model to estimate the average vapor concentration within each zone, a 

average exposure is calculated as follows:

= Concentration of vapor within Zone x; and

= Percent of time spent in Zone x by the worker.

The term representing Zone 4 drops out because there is no exposure to refrigerant vapors in Zone 

term (i.e., 30-minute) worker exposures to refrigerant vapors and gas

it is assumed that 25 percent of the daily emission is released over a 30-minute period. 

DISCUSSION OF RESULTS

The attached tables (Attachment 5-A) show the modelling results for each end

on, and alternative refrigerant. For each scenario, the tables report the average 

weighted average (TWA) concentrations of refrigerant present in each 

of the zones, and the estimated 8-hour and 30-minute TWA levels to which worke

1 summarizes the occupational exposure limits for the alternative refrigerants 

that were used to determine whether workers may be exposed to potentially hazardous airborne 

gas or vapor concentrations. Exhibit 5-2 summarizes the results for those scenarios where the 

model suggests that worker exposures may exceed either the 8-hour or 30-minute occupational 

exposure limit for the alternative refrigerant. The highest exposures are predicted to occur during 

disposing of industrial process (high pressure build-up) refrigeration 

Interpretation and Comparison of Model Results with Sampling Data

operations involving refrigerators and freezers, other refrigeration appliances, and mobile air 

hour shift. For all other 

represents the volume of space in which the worker is performing his or her 

work duties. For each exposure scenario, it is assumed that a worker spends a certain percentage 

of time within each of the four zones, as follows. For manufacturing and installation operations, 

hour workday in Zone 1, 

10 percent in Zone 4. For repair operations, it is 

assumed that a worker spends 20 percent of the workday in Zone 1, 40 percent in Zone 2, 20 

percent in Zone 3, and 20 percent in Zone 4; this reflects the likely possibility that, in repair 

ompared to manufacturing or installation operations, a worker will spend a larger 

proportion of the workday in close proximity to the emission source, but will also spend a greater 

repair site.

After using the box model to estimate the average vapor concentration within each zone, a 

The term representing Zone 4 drops out because there is no exposure to refrigerant vapors in Zone 

minute) worker exposures to refrigerant vapors and gasses, 

minute period. 

A) show the modelling results for each end-use sector, 

on, and alternative refrigerant. For each scenario, the tables report the average 

weighted average (TWA) concentrations of refrigerant present in each 

minute TWA levels to which workers may be 

1 summarizes the occupational exposure limits for the alternative refrigerants 

that were used to determine whether workers may be exposed to potentially hazardous airborne 

he results for those scenarios where the 

minute occupational 

exposure limit for the alternative refrigerant. The highest exposures are predicted to occur during 

up) refrigeration 

Interpretation and Comparison of Model Results with Sampling Data
107

Several observations suggest that the model will tend to overstate likely occupational 

exposures to alternative refrigerant vapors and gasses. First, the emission estimates from the 
108

EXHIBIT 5-1

OCCUPATIONAL EXPOSURE LIMITS FOR

POTENTIAL ALTERNATIVE REFRIGERANTS*

Substitute

Material WGL (ppm) EGL (ppm)

HCFC-22 1,000 5,000

HFC-23 1,000 3,000

HCFC-123 30 2,500

HCFC-124 1,000 3,000

HFC-125 1,000 3,000

HFC-134a 1,000 3,000

HFC-143a 1,000 3,000

HCFC-142b 1,000 5,000

HFC-152a 1,000 4,000

HFC-227ea 1,000 3,000

* This table may contain or utilize exposure limits that are not Agency verified or that were 

updated after this chapter was written. Chapter 3 presents the most recent exposure limits for 

each chemical, identifies which are verified versus estimated values, identifies methods used to 

derive estimated values, and provides information sources.

Vintaging model are considered to be worst-case estimates. Second, the assumptions regarding 

air exchange rates for each of the work zones do not reflect the use of any local exhaust ventilation, 

which is likely to be used in manufacturing and disposal operations involving any significant 

releases.

The use of properly designed local exhaust ventilation or other means of isolating the 

worker from emission sources would likely prevent gas or vapor concentrations from exceeding 

the occupational exposure limits most of the time. Given the assumed sizes of many of the 

potential releases (some of them exceeding a few hundred pounds), it would appear unlikely that 

an employer would conduct such operations without providing some means of mechanical 

ventilation. It is for this reason that the exposure estimates for high-pressure industrial process 

refrigeration systems are certain to be unrealistically high. In addition, for each release scenario, 

it is assumed that the entire estimated daily release occurs over a single 8-hour workday and at a 

single location. This is not the case for many scenarios, and particularly for manufacturing 

operations, where the estimated daily release may occur over two or three workshifts or where the 

release may be spread out over two or more production lines. Finally, most of the predicted 

exceedances over the occupational exposure limits are the result of assuming that there will be no 

recycling of HFC refrigerants. To the extent that recycling technologies are used, exposures to 

HFCs should be below the occupational exposure limits for these compounds.

The model's tendency to overstate worker exposures is further supported by sampling data 

obtained for HCFC-123 refrigerant during repair operations conducted on low-pressure
109

EXHIBIT 5-2

SUMMARY OF ESTIMATED WORKER EXPOSURE TO ALTERNATIVE REFRIGERANTS

FOR SCENARIOS WHERE THE OCCUPATIONAL EXPOSURE LIMIT IS EXCEEDEDa

8-Hour TWAb30-Minute TWA

End-Use Sector Operation Substitute

Materialc

Predicted

Exposure (ppm) Operation SubstituteMaterialc

Predicted

Exposure (ppm)

Retail Food (Parallel 

System)

Disposal HFC-134a

HFC-125

HFC-143a

HFC-23

1,579

1,342

1,917

2,300

Disposal HFC134a

HFC-125

HFC143a

HFC-23

4,742

4,030

5,757

6,909

Cold Storage Warehouses Disposal HFC-152a

HFC-23

1,309

1,234

Centrifugal Chillers (Low 

Pressure)

Manufacture HCFC-123 73d

Centrifugal Chillers (High 

Pressure)

Disposal HFC-124

HFC-134a

HFC-227ea

2,271

3,050

1,647

Disposal HFC-124

HFC-134a

HFC-227ea

6,819

9,159

4,928

Industrial Process (Low 

Pressure)

Manufacture

Repair

HCFC-123

HCFC-123

54

49
110

EXHIBIT 5-2 (continued)

SUMMARY OF ESTIMATED WORKER EXPOSURE TO ALTERNATIVE REFRIGERANTS

FOR SCENARIOS WHERE THE OCCUPATIONAL EXPOSURE LIMIT IS EXCEEDEDa

8-Hour TWAb30-Minute TWA

End-Use Sector Operation Substitute

Materialc

Predicted

Exposure (ppm) Operation SubstituteMaterialc

Predicted

Exposure 

(ppm)

Industrial Process

 (High Pressure 

Build-Up)

Manufacture

Disposal

HFC-143a

HFC-152a

HFC-134a

HFC-152a

HFC-125

HFC-143a

HFC-23

1,293

1,016

30,840

47,661

15,740

18,375

13,490

Manufacture

Disposal

HFC-134a

HFC-143a

HFC-152a

HFC-134a

HFC-152a

HFC-125

HFC-143a

HFC-23

3,941

7,751

6,090

92,608

143,122

47,266

56,260

40,509

Large Ice Makers Repair HFC-152a 1,076

Ice Rinks Disposal HFC-134a

HFC-152a

HFC-23

4,609

7,123

2,016

Disposal HFC-134a

HFC-152a

HFC-23

13,840

21,390

6,054

Central A/C and Home 

Heat Pumps

Manufacture HFC-152a 1,332

a

Exposure levels are rounded to the nearest whole number.

b

Time-weighted average.

c

The refrigerant blends analyzed for these sectors may be considered confidential business information (CBI) by the manufacturer. As a 

result, the identification of the constituents of any blend and the proportion of each constituent contained in any blend are not presented 

in this exhibit.

d One manufacturer's representative states that worker exposures to HCFC-123 during centrifugal chiller manufacture are typically 1 ppm 

or less, due to the use of exhaust ventilation.
111

centrifugal chillers (EPA 1991). This study showed that worker exposures were generally well 

below 1 ppm as an 8-hour TWA during repair operations involving the use of recycling equipment; 

however, results from the model suggest that workers may be exposed to about 4 ppm HCFC-123 

during these repair operations, even when proper recycling is used. For the manufacture of 

low-pressure centrifugal chillers, the model suggests that workers could be exposed to HCFC-123 

concentrations as high as 73 ppm as an 8-hour TWA; however, a representative of one 

manufacturer indicated that, due to the use of local exhaust ventilation, worker exposures were 

typically in the range of 1 ppm (personal communication).

The analyses presented above did not consider the use of ammonia, butane, propane, or 

perfluoropropane as alternative refrigerants. However, existing OSHA and ASHRAE standards 

governing the handling and use of these materials should serve to limit occupational exposures to 

them. Currently, OSHA enforces permissible exposure limits (PELs) for two of these materials: 

ammonia (50 ppm as an 8-hour TWA), and propane (1000 ppm as an 8-hour TWA). In addition, 

ASHRAE classifies butane and propane as "highly flammable" refrigerants, and ammonia as a 

"moderately flammable" refrigerant having high toxicity (ASHRAE Standard 34); as such, special 

requirements set forth in ASHRAE Standard 15 apply to the use of these materials as refrigerants. 

These requirements include:

 Prohibiting the use of any of these refrigerants in systems designed for human 

comfort;

 Limiting the amount of refrigerant that can be used in systems installed in occupied 

areas;

 Requiring the use of vapor detection alarms that activate when concentrations of 

refrigerant exceed toxic or explosive levels; and

 Prohibiting the use of butane or propane in any system installed in commercial or 

institutional buildings (i.e., only industrial use is permitted).

5.4 POTENTIAL WORKPLACE FLAMMABILITY AND EXPLOSIVITY RISKS

One of the alternative refrigerants considered in this analysis, HFC-152a, has been 

classified as a moderately flammable material under proposed ASHRAE Standard 34. It has a 

lower flammability limit (LFL) of 4.4 percent in air (44,000 ppm) and a heat of combustion of less 

than 19,000 kJ/kg. As such, it represents a lesser fire and explosion risk than propane or butane, 

which have LFL's that are less than half that of HFC-152a and heats of combustion greater than 

19,000 kJ/kg.

The risk of fire or explosion in an industrial setting arises when local concentrations of a 

flammable or explosive gas or vapor are allowed to exceed the lower flammable limit for the gas or 

vapor in the presence of an ignition source (i.e., flame, heat, electrical energy, or static sparks). In 

general, when handling flammable or explosive materials, most industrial facilities consider that 

accumulations of gas or vapor concentrations of from 10 to 25 percent of the LFL or higher for that 

substance represent an emergency situation that requires corrective action. For HFC-152a, an 

emergency concentration would therefore be considered to exist if concentrations exceeded 4,400 

to 11,000 ppm (i.e., 10 to 25 percent of the LFL).
112

The exposure assessment analysis presented above shows that, under worst-case 

assumptions and assuming no recycling, local short-term concentrations of HFC-152a would not 

be expected to exceed 4,400 ppm under normal operating conditions in all but one end-use sector 

(high-pressure industrial process refrigeration). As stated above, EPA believes that the exposure 

estimates for this end-use sector are unrealistically high because of the assumption that no 

mechanical ventilation would be used during operations involving the release of such large 

quantities of refrigerant. Thus, with the appropriate use of equipment designed for the safe use of 

flammable or explosive gases and with the use of mechanical ventilation systems, concentrations 

of HFC-152a are not likely to exceed 10 percent of the LFL and should therefore not present a 

substantial fire or explosion risk in the workplace. Isolation of potential ignition sources (such as 

welding operations conducted on the assembly line) from processes involving the handling of 

HFC-152a, and the use of combustible gas detectors and alarm systems, will serve to further 

reduce this potential risk.
113

CHAPTER 5 REFERENCES

NIOSH (Mutchler, J.E.) 1973. "Principles of Ventilation." The Industrial Environment--It's 

Evaluation and Control. NIOSH, Center for Disease Control, U.S. Department of 

Health and Human Services. ch. 39.

U.S. EPA. 1990. Revised Draft: Occupational Exposure and Environmental Release Data for 

Chlorofluorocarbons (CFCs) and Their Substitutes. Office of Toxic Substances.

U.S. EPA. 1991. Results of Employee Exposure Monitoring for HCFC-123 at Centrifugal 

Chiller Installations. Final Report. November, 1991.
ATTACHMENT 5-A
6. CONSUMER EXPOSURE AND RISK SCREENING ANALYSIS

This chapter presents a screening level assessment of the risks to consumers from releases 

of CFC substitutes used in home appliances (refrigerators and freezers, central air conditioners, 

window air conditioners, and miscellaneous refrigerated appliances) and automobile air 

conditioners. These are the only applications in the refrigeration and air conditioning sectors that 

have consumer end uses. 

The end uses and substitutes evaluated in this chapter are presented below. The 

composition of one -- R200b -- is confidential:

 Refrigerators and Freezers:

C HCFC-22

C HFC-134a

C HFC-152a

C HCFC-22/HCFC-142b

C HCFC-22/HFC-152a/HCFC-124

C R200b

 Dehumidifiers: Same as refrigerators and freezers.

 Central Air Conditioners and Home Heat Pumps:

C HFC-125

C HFC-134a

C HFC-125/HFC-143a

C HFC-23/HFC-134a

C HFC-125/HFC-143a/HFC-134a

C HCFC-22/propane/HFC-125

 Window Air Conditioners: 

C HFC-125

C HFC-134a

C HFC-125/HFC-143a

C HFC-23/HFC-134a

 Mobile Air Conditioners:

C HFC-134a

C HCFC-22/HFC-152a/HCFC-124

This chapter first presents an assessment of consumer exposure to releases from home 

appliances, followed by an analysis for mobile air conditioners. The analyses performed are 

screening analyses whose purpose is to identify the proposed substitutes for all end uses that may

pose any potential concern for human health or environmental risk. As a result, the analyses 
employ conservative assumptions that tend to overestimate potential risk. Considerable 

uncertainty exists in these analyses.
117

6.1 HOME APPLIANCES

Three types of releases from home appliances are of interest for consumer exposure and 

risk: (1) routine operating leakage, (2) releases during servicing, and (3) accidental releases. 

A report on consumer exposure to CFCs and their substitutes prepared for EPA (Versar 

1990) examined exposures from leakage and servicing releases from refrigerators, freezers, and 

dehumidifiers. Using engineering estimates of releases as input to an equation given on page 4-5 

of this report, average annual concentrations of CFC substitutes were calculated in median-sized 

and 10th percentile-sized homes. Because this consumer exposure analysis spreads the releases 

and resulting concentrations over a year's time, it assesses only long-term, chronic exposures. It 

does not address potential risks from short-term exposure to higher concentrations that result from 

servicing or accidental releases.

Below, potential risks from chronic exposures are examined by comparing estimated doses 

from the consumer exposure report to toxicity values for the CFC substitutes. Subsequently, a 

screening analysis of potential risks associated with higher, but shorter-term, exposures is 

presented. Finally, potential safety concerns from the use of HFC-152a in household refrigerators 

are discussed.

6.1.1 Risks from Long-term Exposure to Leakage and Servicing Events C Previous 

Estimates

The consumer exposure report estimated releases from refrigerators, freezers, and 

dehumidifiers with refrigerant charge sizes ranging from about 140 to 570 g. The annual leakage 

rate was assumed to be 0.2 percent of the charge (0.28 to 1.1 g), and the servicing emission was 

assumed to be 85 g.

The estimated average annual concentrations in two different house sizes C a median size 

of 411 m

3

(equivalent to 1,808 ft2, assuming an 8-ft ceiling height) and a 10th percentile size of 174 

m

3

(766 ft2, assuming an 8-ft ceiling)14 C ranged from 0.4 μg/m3to 3.7 μg/m

3

for annual leakage. 

To estimate potential risk from chronic exposure to leakage, the consumer exposure report's 

exposure information was combined with available toxicity information as follows:

 To evaluate noncarcinogenic effects, the modeled exposure concentrations were 

compared to reference concentrations (RfCs).

 To calculate cancer risks, a lifetime average daily dose of the substitute was 

estimated using the exposure concentration, a 20 m3/day inhalation rate, and a 70 

kg body weight.

The RfCs and cancer slope factor used in this assessment are given in Chapter 3 of this document.

The highest estimated average annual exposure for routine leakage from the consumer 

exposure report C 3.7 μg/m3 C is well below the RfCs for all substitutes. Only one of the 

substitutes C HCFC-22 C is a possible carcinogen. Assuming that people are exposed to an 

 

 

14 The consumer exposure report prepared by Versar also assumed a ventilation rate of 0.2 ACH, that 

is, 0.2 air exchanges per hour.
118

HCFC-22 concentration of 3.7 μg/m324 hours per day, 365 days per year, over a 70-year lifetime, 

the cancer risk for HCFC-22 is 2.1E-07.15 Based on EPA guidelines regarding levels of risk, 

chronic health effects from long-term exposure to routine leakage of CFC substitutes from home 

appliances are not of concern.

 

 

15 In this chapter, where numeric notation is used that includes the term "E-0x" (for example, 

2.1E-07), it is equivalent to 10-x(for example, 2.1 x 10-7). 
119

The consumer exposure report estimated the typical servicing emissions from all pieces of 

equipment to be 85 grams per service. During a year in which the equipment is serviced once, the 

report calculated average annual concentrations ranged from 118 μg/m3 for a median-sized house 

to 279 μg/m3 for a house sized in the 10th percentile. These are also well below the RfCs for the 

substitutes. If it is assumed that servicing occurs once every year and that people spend all of 

their time at home, the cancer risk associated with lifetime exposure to HCFC-22 would be 

6.7E-06 in the median house and 1.6E-05 in the smaller house. However, these values overstate 

potential cancer risks because (1) home appliances such as refrigerators, freezers, and humidifiers 

are serviced much less frequently than once a year; and (2) people typically do not spend all of 

their time at home. Given these factors, EPA believes that actual cancer risks are well below 10-5, 

the threshold level of concern.

6.1.2 Risks from Short-term Exposure During Servicing and Accidental Releases

The next step was to examine potential health risks from short-term exposure to 

temporarily higher concentrations associated with servicing emissions and accidental releases. 

Four situations were examined:

 Exposure to vapors from refrigerators or freezers located in the kitchen;

 Exposure to vapors from a dehumidifier located in a room;

 Exposure to vapors from a central air conditioner or heat pump, where the release 

occurs in the basement; and

 Exposure to vapors from a window air conditioner located in a room.

Approach

To simulate the initial increase and subsequent decrease in airborne concentrations 

resulting from refrigerant releases, the same "box model" approach was used as in the previous 

analysis of occupational exposure (see Chapter 5). This model was derived from a differential 

material balance that, when integrated, provides a basis for relating the air concentration of a 

contaminant to the generation and removal rates of the contaminant. 

To calculate releases, it was assumed that the amount of substitute released was equal to 

the amount of CFC released. CFC release information was derived from input files to the 

Vintaging Model.16 The following assumptions concerning releases were made for this analysis:

 Servicing releases occur over 15 minutes. HCFCs are recycled at servicing (under 

Section 608 of the Clean Air Act, HCFC recycling became mandatory in 1992). 

Because HFC recycling will not be mandatory until 1995, servicing releases for 

HFCs are calculated both with and without recycling. If there is no recycling, the 

entire charge is released. The releases are as follows:

 

 

16 The Vintaging Model was developed by ICF to estimate the costs and environmental releases 

associated with a CFC and halon phaseout. For further information, see Chapter 4.
120

Recycling No Recycling

Refrigerators and Freezers 15 g 300 g

Dehumidifiers 20 g 400 g

Central A/Cs and Heat Pumps 80 g 3,840 g

Window Air Conditioners 40 g 1,820 g

 Accidental releases are modeled as leakage of the entire charge over two different 

time frames: 15 minutes and four hours. The releases are the same as those listed 

above under the "no recycling" scenario.

The following inputs were made to the box model:

 Room sizes:

C 411 m3for house volume (equivalent to 1,808 ft2, assuming an 8-ft ceiling 

height);

C 18 m3(79 ft2) for the kitchen;

C 102 m3(449 ft2) for the basement; and

C 41 m

3

(180 ft2) for the room housing the window A/C or miscellaneous unit.

 Air exchange rate:

C 0.25 air changes per hour (ACH) for the house, basement, and room; and

C 2.3 ACH for the kitchen.

Thirty minute time weighted average (TWA) exposures were calculated and compared to 

the interim emergency guidance levels (EGLs) shown in Chapter 3.

Results

Exhibits 6-1 through 6-4 show the 30 minute average concentrations and their ratios to the 

interim EGLs for the relevant substitutes. (The values shown in these tables are based on the 

substitute being composed of 100 percent of the named chemical. In practice, some substitutes 

would be used only in a blend.) The results are discussed below.

The results show that servicing with recycling never results in concentrations above the 

EGL. All of the other scenarios involve release of the entire charge. This can result from an 

accident or C for the HFCs only C from a servicing event that does not involve recycling. The 

modeling indicates that, unless otherwise noted, the concentrations of the following substitutes or 

combinations of substitutes never exceed the EGL even if the entire charge is released:

 Refrigerators and freezers:

C HCFC-22;

C HFC-134a;

C HFC-152a;
121

EXHIBIT 6-1

30-MINUTE AVERAGE CONCENTRATIONS FROM SERVICING

AND ACCIDENTAL RELEASES, AND RATIO TO

INTERIM EMERGENCY GUIDANCE LEVELS (EGLs):

REFRIGERATORS AND FREEZERS

Service, With 

Recycling

Service, 

Without 

Recycling

Accidental 

15-Min.

Release

Accidental 

4-Hr Release

KITCHEN

30-Min. TWA, mg/m3

Ratio to EGL:

 HCFC-22

 HCFC-124

 HCFC-142b

 HFC-134a

 HFC-152a 

 HFC-227ea

 430 

 0.025

 0.025

 0.022

 0.034

 0.032 

 0.020

 10,000

 NA

 NA

 NA

 0.79

 0.74 

 0.48

 10,000

 0.57

 0.58

 0.50

 0.79

 0.74

 0.48

 3,300

 0.19

 0.19

 0.17

 0.26

 0.24

 0.16

HOUSE

30-Min. TWA, mg/m3

Ratio to EGL:

 HCFC-22

 HCFC-124

 HCFC-142b

 HFC-134a

 HFC-152a

 HFC-227ea

 24

 0.0014

 0.0014

 0.0012

 0.0019

 0.0018

 0.0011

 550

 NA

 NA

 NA

 0.044

 0.041

 0.026

 550

 0.031

 0.032

 0.028

 0.044

 0.041

 0.026

 570

 0.033

 0.033

 0.029

 0.045

 0.042

 0.027
122

EXHIBIT 6-2

30-MINUTE AVERAGE CONCENTRATIONS FROM SERVICING

AND ACCIDENTAL RELEASES, AND RATIO TO

INTERIM EMERGENCY GUIDANCE LEVELS (EGLs):

DEHUMIDIFIERS

Service, With 

Recycling

Service, 

Without 

Recycling

Accidental 

15-Min.

Release

Accidental 

4-Hr Release

ROOM

30-Min. TWA, mg/m3

Ratio to EGL:

 HCFC-22

 HCFC-124

 HCFC-142b

 HFC-134a

 HFC-152a

 HFC-227ea

 440 

 0.025

 0.026

 0.022

 0.035

 0.033

 0.021

 6,100

 NA

 NA

 NA

 0.48

 0.45

 0.29

 6,100

 0.35

 0.36

 0.31

 0.48

 0.45

 0.29

 6,400

 0.37

 0.37

 0.32

 0.51

 0.47

 0.30

HOUSE

30-Min. TWA, mg/m3

Ratio to EGL:

 HCFC-22

 HCFC-124

 HCFC-142b

 HFC-134a

 HFC-152a

 HFC-227ea

 42

 0.0024

 0.0025

 0.0021

 0.0033

 0.0031

 0.0020

 610

 NA

 NA

 NA

 0.048

 0.045

 0.029

 610

 0.035

 0.036

 0.031

 0.048

 0.045

 0.029

 630

 0.036

 0.037

 0.032

 0.050

 0.047

 0.030
123

EXHIBIT 6-3

30-MINUTE AVERAGE CONCENTRATIONS FROM SERVICING

AND ACCIDENTAL RELEASES, AND RATIO TO

INTERIM EMERGENCY GUIDANCE LEVELS (EGLs):

CENTRAL AIR CONDITIONERS AND HOME HEAT PUMPS

Service, With 

Recycling

Service, 

Without 

Recycling

Accidental 

15-Min.

Release

Accidental 

4-Hr Release

BASEMENT

30-Min. TWA, mg/m3

Ratio to EGL:

 HCFC-22 

 HFC-23

 HFC-125

 HFC-134a

 HFC-143a

 590

 0.034

 0.069

 0.040

 0.047

 0.058 

 28,000

 NA

 3.3

 1.9

 2.2

 2.7 

 28,000

 1.6

 3.3

 1.9

 2.2

 2.7

 29,000

 1.7

 3.4

 2.0

 2.3

 2.8 

HOUSE

30-Min. TWA, mg/m3

Ratio to EGL:

 HCFC-22

 HFC-23

 HFC-125

 HFC-134a

 HFC-143a

 150

 0.0086

 0.018

 0.010

 0.012

 0.015 

 7,000

 NA

 0.82

 0.48

 0.56

 0.69 

 7,000

 0.40

 0.82

 0.48

 0.56

 0.69 

 7,200

 0.41

 0.84

 0.49

 0.57

 0.71 
124

EXHIBIT 6-4

30-MINUTE AVERAGE CONCENTRATIONS FROM SERVICING

AND ACCIDENTAL RELEASES, AND RATIO TO

INTERIM EMERGENCY GUIDANCE LEVELS (EGLs):

WINDOW AIR CONDITIONERS

Service, With 

Recycling

Service, 

Without 

Recycling

Accidental 

15-Min.

Release

Accidental 

4-Hr Release

ROOM

30-Min. TWA, mg/m3

Ratio to EGL:

 HFC-23

 HFC-125

 HFC-134a

 HFC-143a

 740

 0.087

 0.050

 0.059

 0.073

 34,000

 4.0 

 2.3

 2.7

 3.3

 34,000

 4.0

 2.3

 2.7

 3.3

 34,000

 4.0

 2.3

 2.7

 3.3

HOUSE

30-Min. TWA, mg/m3

Ratio to EGL:

 HFC-23

 HFC-125

 HFC-134a

 HFC-143a

 74

 0.0087

 0.0050

 0.0059

 0.0073

 3,300

 0.39

 0.22

 0.26

 0.32

 3,300

 0.39

 0.22

 0.26

 0.32

 3,400

 0.40

 0.23

 0.27

 0.33
125

C R200b. The weighted average of the ratios is below 1.0, indicating that 

this blend is of no concern even if the health hazards are additive.

C HCFC-22/HCFC-142b. The weighted average of the ratios is below 1.0, 

indicating that this blend is of no concern even if the health hazards are 

additive.

C HCFC-22/HFC-152a/HCFC-124. The weighted average of the ratios is 

below 1.0, indicating that this blend is of no concern even if the health 

hazards are additive.

Releases from refrigerators and freezers are based on a charge size of 300 g. A

conservative estimate of charge sizes for refrigerators and freezers is 240 g for 

refrigerators and 340 g for freezers. Since more people own refrigerators than 

freezers, the estimated charge size of 300 g used in this analysis actually overstates 

releases and exposures for most of the population.

 Dehumidifiers:

C HCFC-22;

C HFC-134a;

C HFC-152a;

C R200b. The weighted average of the ratios is below 1.0, indicating that 

this blend is of no concern even if the health hazards are additive.

C HCFC-22/HCFC-142b. The weighted average of the ratios is below 1.0, 

indicating that this blend is of no concern even if the health hazards are 

additive.

C HCFC-22/HFC-152a/HCFC-124. The weighted average of the ratios is 

below 1.0, indicating that this blend is of no concern even if the health 

hazards are additive.

Under the assumptions used in this analysis, all of the other substitute/end use 

combinations result in exposures above the EGL if the entire charge is released:

 Central air conditioners and home heat pumps: None of these compounds or 

blends exceed their EGLs in the house. In the basement, however, all alternatives 

(taken either individually or as blends) exceed their EGLs. These figures are 

based on the assumption that about 20 percent of central air conditioners and home 

heat pumps have a charge size of 3,800 g, about 75 percent have a charge size of 

3,000 g, and 5 percent have a charge size of 700 g.

 Window air conditioners: All alternatives exceed their EGLs in the room where 

the air conditioner is located. All window air conditioners are assumed to have a 

charge size of 1,800 g.
126

As discussed above, these results are based on a comparison of 30-minute TWA exposures with 

interim EGLs. Another way to approach this assessment would be to calculate shorter-term 

exposures and compare them to the cardiotoxic LOAELs or NOAELs given in Chapter 3. If EPA

were to calculate 15 minute TWA exposures for the scenarios with 15-minute releases (i.e., 

servicing without recycling, 15-minute accidental release), the TWA exposures would be well 

below the cardiotoxic NOAELs and LOAELs for every substitute.

6.1.3 Summary of Modeling Results

Analysis has shown that unless the entire refrigerant charge is released over a short period 

of time, none of the substitutes exceed EPA's threshold of concern for human health risk in any

piece of equipment. Routine leakage and servicing with recycling simply will not release enough 

refrigerant to pose significant short-term or long-term risks to human health.

If the entire charge is released, the calculated 30-minute average concentrations exceed the 

EGLs for substitutes in air conditioning equipment. The following factors should be considered 

when judging whether these exceedances are cause for concern:

 Recycling at servicing will be required for the HFCs by 1995. Until then, EPA 

believes that most HFCs will be recycled anyway, because of their high cost 

relative to CFCs.

 Accidental releases of an entire refrigerant charge occur infrequently. The UNEP 

(1992) reports that less than 5 percent of the refrigerators and freezers have 

accidental releases of the entire charge.

 The analysis is based on conservative assumptions:

C Exposures are generally calculated for the equipment with the largest 

charge size.

C All releases are assumed to occur indoors. This is not necessarily the case 

for central air conditioners, home heat pumps, and window air conditioners.

C It was assumed that people remain in the room in which the release occurs 

for 30 minutes.

C Air exchange rates estimated are conservative; they reflect an energy

efficient house with no windows or doors open.

C The EGLs that are used as toxicity benchmarks are conservative, and 

incorporate a margin of safety. A similar approach based on cardiotoxic 

LOAELs or NOAELs would show that exposures are below the concern 

level.

6.1.4 Safety Concerns: HFC-152a in Household Refrigerators

The release of HFC-152a in a household kitchen can potentially cause personal injury in a 

few ways:

 injury from sudden overpressure (i.e., shock wave);
127

 injury from shrapnel resulting from an explosion; and

 injury from thermal radiation.

The likelihood and severity of these risks were studied in a report on risk assessment of flammable 

refrigerants for home appliances. (EPA 1991). Using a mathematical model to relate vapor 

concentration to peak overpressure, the report found that the sudden ignition of a typical charge of 

HFC-152a would be sufficient to cause eardrum rupture of a person who was in the kitchen at the 

time of ignition. The explosion would also likely cause structural damage to the house. 

However, the report also found that sudden ignition of a full charge was an extremely unlikely 

event; rather, there would be some dispersion of HFC-152a vapor below the lower flammable limit 

of 4.4 percent, and thus the subsequent event would be limited to a vapor fire rather than an 

explosion.

Using information on historical leakage rates coupled with a fault tree analysis, the report 

predicts that the probability of a fire or explosion due to an external refrigerant leak is

2.0 x 10-8/yr (5.0 x 10-7under worst-case assumptions). The probability of an explosion due to 

leakage of HFC-152a inside the refrigerator is considerably smaller (2.7 x 10-13/yr under 

average-case assumptions and 7.0 x 10-12/year under worst-case assumptions).

6.2 MOBILE AIR CONDITIONERS (MACs)

6.2.1 Approach Used in a Previous Consumer Exposure Report

The consumer exposure report (Versar 1990) estimated MAC emissions to which 

consumers could be exposed as the product of four factors: (1) total charge of refrigerant in the 

system; (2) fraction of refrigerant that leaks from the system before it is noticed and repaired; (3) 

fraction of refrigerant entering the vehicle passenger compartment; and (4) frequency of leak 

episodes.

 Total charge: Total refrigerant charge is based on averages from a previous study

(Chilton 1985) for four vehicle class sizes: subcompact, 27 ozs.; compact, 38 ozs.; 

midsize, 47 ozs.; and large, 53 ozs.

 Total refrigerant leaked before being noticed/repaired: In newer vehicles with 

protection devices and in warmer climates, the consumer exposure report assumed 

that leaks would be noticed and fixed quickly. In cooler climates and older cars 

without protection devices, a MAC leak would probably go unnoticed until most of 

the refrigerant had leaked. Overall, the report assumed an average leak of 50 

percent of charge capacity.

 Fraction of leak entering passenger compartment: This parameter depends on the 

location of the leak (evaporator case or engine compartment) and whether the 

vehicle is in motion or stationary. The consumer exposure report assumed that the 

vehicle is stationary 15 percent of the time that it is in use; that the air conditioning 

or heat are on 2/3 of the time a vehicle is in operation; and that the average annual 

consumer vehicle operation time is 526 hours.

 Leak episodes per vehicle: The consumer exposure report assumed that there are 

0.76 leaks/yr/vehicle.
128

Leaks from the evaporator case result in infiltration of the entire release into the passenger 

compartment, and therefore the highest consumer exposures. Therefore, the remainder of this 

discussion focuses on evaporator case leaks. The consumer exposure report's emission 

calculations for evaporator case leaks are as follows:

Emissions, g/yr = (oz. charge/vehicle class) x (0.50 fraction emitted) x (28.35 g/oz) 

x (0.76 leaks/yr)

Size class Emissions, g/yr

Subcompact 290

Compact 409

Midsize 506

Large 602

When a leak occurs in the evaporator case, the rate of air intake affects the concentration of 

the refrigerant in the passenger compartment by either circulating the compartment air out of the 

vehicle (high ventilation rate) or letting the air stand in the compartment (low ventilation rate), 

allowing refrigerant concentrations to build up. The consumer exposure report assumed that the 

MAC is working at maximum level while it is on, minimizing ventilation. The average speed of 

travel for a vehicle, according to this report, is 30 mph, yielding a 27 ACH (27 full compartment 

volumes/hour) ventilation rate. Concentrations are then calculated in terms of buildup of 

refrigerants in the recirculated air. Refrigerant concentrations also depend on passenger 

compartment sizes, which are broken down into the same four units by a previous study (Chilton 

1985): subcompact vehicles, 2.3 m3; compact, 2.5 m3; midsize, 2.8 m3; and large, 3.1 m3. 

The consumer exposure report's calculated passenger compartment concentrations are as follows:

Concentration, mg/m3= (emissions, g/yr) x (1 yr/8760 hrs) x (ventilation rate, 

1 hr/27) x (1000 mg/g) x (1/passenger compartment volume, m3) =

Size class Concentration, mg/m3

Subcompact 0.53

Compact 0.69

Midsize 0.76

Large 0.82

Comparing these concentrations to reference concentrations (RfCs) for the substitutes (see 

Chapter 3) shows that the highest estimated passenger compartment concentration (0.82 mg/m3) is 

far below all of the RfCs.

HCFC-22 is the only possible carcinogen of the four substitutes analyzed in the study. If 

the consumer exposure report's exposure assumptions are used (inhalation rate is 0.6 m3/hr for a 

driving adult; average consumer vehicle operation time is 526 hours per year), the lifetime cancer 

risk is 2.0 x 10-6.

6.2.2 Comparison of Parameters Contained in Consumer Exposure Report with Data 

from Other Sources

Some of the parameters built into the consumer exposure report's MAC analysis (Versar 

1990) are also included in EPA's Vintaging Model and the Market Vision Research Report. 

Parameters addressed by both the consumer exposure report and one of these other sources 
129

include: (1) total MAC charge; (2) total charge lost before leak is detected and fixed; (3) frequency

of operational leak events; and (4) emissions to the vehicle passenger compartment. Below, the 

values used in these other sources are compared to those used by the consumer exposure report. 

 Total MAC charge: While the consumer exposure report assumed 53 oz. 

maximum for total refrigerant charges, the Vintaging Model uses a less 

conservative 42.3 oz. upper bound.

 Total charge lost before the leak is detected and fixed: The Vintaging Model 

assumes a loss of 30 percent of the initial charge, substantially less than the more 

conservative average of 50 percent loss of initial charge used by the consumer 

exposure report.

 Frequency of operational leak events: According to the consumer exposure 

report, the frequency of leak events is 0.76 leaks/car/year. This value is based on 

an Automotive Refrigeration Products Institute study in which 384 recharges were 

performed on 506 air-conditioned vehicles in one year. According to the 

Vintaging Model, 37 percent of cars with MACs have their MACs serviced in any

given year. Thus, the servicing (and therefore, leakage) frequency in the 

consumer exposure report is about two times higher than the Vintaging Model.

 Total emissions to the passenger compartment: The Vintaging Model assumes 

that upper end operating releases from MACs are about 100 grams per year. This 

is much lower than the upper end of 602 grams per year assumed by the consumer 

exposure report.

All else being equal, a decrease in the value of any of these parameters would result in 

reduced risk. As shown above, the values assigned to these parameters by the other sources are 

always lower than those used by the consumer exposure report. Therefore, any adjustments that 

might be made to the consumer exposure analysis to be consistent with these other sources would 

only serve to reduce the already-low exposures and associated health risks.

6.2.3 Summary

The consumer exposure report estimated consumer exposure to emissions of CFC 

substitutes from MACs. These exposure levels are below those that would raise concern for 

human health risks. An examination of this report's inputs and assumptions indicates that the 

analysis is conservative, confirming that consumer exposure is not of concern.
130

CHAPTER 6 REFERENCES

Automotive Refrigeration Products Institute. 1988. 1988 Private Sector Vehicle Refrigerant 

Consumption Study. Published by the Automotive Refrigeration Products Institute, 

Lanham, MD.

Chilton. 1985. Chilton's Guide to Air Conditioning Repair and Service. Chilton Book Co., 

Radnor, PA.

Market Vision Research Report. Results from survey work performed for the Automotive 

Refrigerant Products Institute.

U.S. EPA. 1991. Risk Assessment of Flammable Refrigerants for Use in Home Appliances, 

Revised Draft Report. Global Change Division. September 10, 1991.

Versar Inc. 1990. June 19. Revised Draft Final Report, Consumer Exposure to Chlorinated 

Fluorocarbons (CFCs) and CFC Substitutes. 
7. GENERAL POPULATION EXPOSURE AND RISK ANALYSIS

This chapter presents a screening level assessment of the risks to the general population 

from exposure to ambient air releases of substitutes for CFCs in the refrigeration and air 

conditioning sectors. EPA previously performed a similar study (EPA 1990a) using data from 

another report (EPA 1990c). Since then, more recent data on CFC emissions from refrigeration 

and air conditioning equipment have been collected and a new analysis conducted. The 

evaluation of substitutes has also been expanded to include compounds not previously included in 

EPA reports.

This analysis assesses each of 20 main end uses in the refrigeration and air conditioning 

sectors. To develop this list of 20 end uses, the 49 end uses covered by the Vintaging Model17

were subdivided into equipment types with similar charge sizes and emission rates. For each end 

use, this report examines compounds identified by EPA as possible substitutes for present CFC 

use. The list of end uses and substitutes is presented in Attachment 7-A.

The substitutes are grouped into four categories for this analysis: (1) the HCFCs and 

HFCs; (2) other alternative refrigerants, including ammonia, butane, isobutane, propane, 

perfluoropropane, cyclopropane, and dimethyl ether; (3) chlorine; and (4) lithium bromide/water 

absorption and ammonia/water absorption. Each category is discussed in a separate section 

below. Alternatives to mechanical refrigeration (e.g., evaporative coolers and turbochillers) are 

not analyzed, since these alternatives do not use chemical refrigerants and therefore pose no 

exposure risks to the general population.

The four analyses below are presented as screening analyses. Their purpose is to identify 

the proposed substitutes for all end uses that may pose any potential concern for human health or 

environmental risk. As a result, the analyses employ conservative assumptions that tend to 

overestimate potential risk. Considerable uncertainty exists in these analyses. The reader 

should recognize the caveats and limitations identified throughout the chapter.

7.1 HCFCs AND HFCs

7.1.1 Approach

This analysis of the HCFCs and HFCs uses conservative screening assumptions to estimate 

potential risks. The basic approach is to: (1) estimate high-end annual releases of substitutes 

from equipment manufacturing plants, operating sites, service stations, and recycling centers or 

salvage yards; (2) use generic dispersion factors to calculate concentrations of the substitutes in air 

near the release site; and (3) compare these concentrations to health-based reference 

concentrations (RfCs) and, for carcinogens, calculate cancer risk. These three steps are discussed 

in more detail below.

 

 

17 A complete description of the Vintaging Model and the other methods used to estimate refrigerant 

emissions by equipment type can be found in Chapter 4.
A. Estimating Ambient Air Releases

To estimate releases to ambient air, the first step was to identify the activities that lead to 

emissions and the types of sites at which such activities occur. Activities through which CFC 

substitutes are released to the environment include equipment manufacture, installation, operation, 

servicing, and disposal. The types of sites at which these activities occur include factories, 

operating sites, service stations, and recycling centers or salvage yards.

The second step was to calculate the amount of CFC substitute released during each 

activity. For the screening-level analysis, it was assumed that in all cases the amount of substitute 

released would equal the amount of CFC released presently. Most CFC release information was 

derived from input files to the Vintaging Model; some data were received directly from industry

associations and individual manufacturers.

The emissions values used in the exposure assessment for each end use represent the 

highest values that would be expected to occur as a result of typical refrigeration practices. 

Release estimates for each of the 20 end uses were based on the equipment type with the highest 

emission rate within that end use (generally the equipment with the largest charge size). 

Catastrophic scenarios, such as a factory explosion that could cause temporarily high exposures in 

a nearby town, were excluded.18

Emissions during servicing and disposal are subject to recycling, which can greatly 

decrease the amount of refrigerant released to ambient air. Under Section 608 of the Clean Air 

Act, the recycling of HCFCs became mandatory in 1992. However, HFC recycling will not be 

required until 1995. Therefore, scenarios both with and without recycling were examined for 

HFCs, but only scenarios with recycling for HCFCs.

The third step in estimating releases involved using the information generated in the first 

two steps to calculate the amount of CFC substitute released to the atmosphere, in a year's time, 

from each type of release site. The methods used to calculate these releases are summarized 

below.

 

 

18 Events of this nature are addressed by the Emergency Preparedness and Community Right-to-Know 

Act of 1986 (EPCRA), also known as Title 3 of the Superfund Amendments and Reauthorization Act 

(SARA) of 1986. Under Sections 311 and 312, Material Safety Data Sheets (MSDSs), which provide 

chemical data or lists of chemicals, must be provided to local planning committees and emergency 

personnel to assist their decisionmaking and preparedness in the event of a emergency. Regulated 

chemicals include those posing a physical hazard (e.g., flammability, combustibility, reactivity, corrosivity, 

oxidizing potential, and pressurized gases) or those posing a health hazard (e.g., carcinogens, toxins, and 

irritants). 
133

 Releases from factories: Annual air releases of HCFCs and HFCs from factories 

were calculated by multiplying the number of units manufactured per factory per 

year by the amount of substitute released per unit at the factory. One end use, low 

pressure centrifugal chillers, was an exception. On the recommendation of a 

leading manufacturer, it was assumed that only 20 percent of the units were tested 

(and therefore charged and recovered) at the factory. Data derived from the 

Vintaging Model, and originally from comprehensive industry surveys, were used 

to estimate the total number of pieces of equipment manufactured per year in the 

U.S. In calculating the number of units manufactured per plant per year, unequal 

market share was assumed (i.e., that some manufacturers are larger and produce 

more units per year). More accurate data were used if verifiable information was 

readily accessible. Manufacturing emissions include emissions associated with 

equipment and component testing. Where applicable, charging and leak testing 

emissions were also included.

 Releases from equipment operating sites: To estimate air releases from operating 

sites, the highest possible amount of CFC substitute that could be released from an 

operating site in any given year was calculated, which would be either the year of 

installation or disposal. To do this, the releases from equipment operation, 

servicing, and either installation or disposal were added together, depending upon 

which of the latter two activities' releases was higher. ("Disposal" releases occur 

at the equipment operating site if the charge is drained or removed at the site before 

the equipment is dismantled, which has been assumed in all cases except for 

automobile air conditioners (MACs) and household appliances.)

 Releases from service stations: This release site applied only to the MACs end 

use. Two types of activities that cause emissions typically occur at service 

stations: the installation of after-market MACs and the servicing of MACs. 

Annual air releases associated with each activity were calculated by multiplying the 

number of MACs installed and serviced annually at service stations by the amount 

of substitute released during each installation or servicing. Since Section 609 of 

the CAA mandates the recycling of refrigerants during the servicing of MACs, 

emission estimates for servicing assumed that recycling would occur. The annual 

installation and servicing releases were added together to derive the total annual 

releases from the service station.

 Releases from recycling centers/salvage yards releases: A centralized equipment 

disposal scenario was created for each of two types of end uses C household 

appliances and MACs:

C The disposal scenario for household appliances was based on an actual site 

C an Appliances Recycling Centers of America (ARCA) facility in 

Minneapolis, Minnesota C which processes refrigerators, freezers, room air 

conditioners, and dehumidifiers. Releases were calculated by multiplying 

disposal emissions by the number of appliances processed annually at that 

site.

C The disposal scenario for MACs is a large automobile salvage yard. 

Releases were estimated by multiplying disposal emissions by the number 

of cars processed annually that contain MACs which still possess their 
134

charge. Information on these parameters was obtained from a New Jersey

Department of Environmental Protection study (Aucott 1990).

Attachment 7-B details all of the assumptions used for estimating ambient air releases for 

each end use.

B. Estimating Downwind Concentrations

Downwind concentrations were estimated using the Industrial Source Complex Long Term 

(ISCLT) Dispersion Model, provided by Versar, an Agency contractor, and summarized in 

Attachment 7-C. This approach consisted of converting the release estimates from kilograms per 

year to grams per second, and then multiplying by normalized dispersion factors (in μg/m3per 

g/sec). These calculations yielded fence-line concentrations in μg/m3. Professional judgment 

was used to determine which factors to apply to each type of site. 

C. Screening Potential Risks

To estimate potential risk, exposure information was merged with available toxicity data, 

as follows:

 To evaluate noncarcinogenic effects, the modeled exposure concentrations were 

compared to reference concentrations (RfCs).

 To calculate cancer risks, EPA's standard risk equation was used. A lifetime 

average daily dose of the substitute was estimated using an exposure concentration, 

an average 20 m3/day inhalation rate, and an average body weight of 70 kg. For 

factory releases, the calculated cancer risks were adjusted to account for the 

phaseout of HCFCs. HCFC-22 (a long-lived HCFC) will be phased out of new 

equipment production by 2010; therefore, a person living downwind of a factory

producing equipment using HCFC-22 would be exposed to the substitute for only

18 years (1992 to 2010), instead of the full 70 years which the cancer risk equations 

assume. Thus, a correction factor of 18/70 was used to calculate cancer risks for 

HCFC-22 from factories. Similarly, for HCFC-123, a short-lived HCFC 

scheduled to be out of production by 2015, a correction factor of 23/70 was applied 

to the calculated cancer risks. The reader should note that the projected dates for 

these accelerated phaseouts are tentative and subject to change.

The reference concentrations and cancer potency factors used in this assessment are given in 

Chapter 3 of this document.

7.1.2 Results

All end uses have calculated exposure concentrations well below the reference 

concentrations for each HCFC and HFC substitute. Estimated cancer risks from HCFC-22 and 

HCFC-123 were highest during factory releases, but still below 1E-05, and are therefore not 

considered to be of concern. Exhibit 7-1 summarizes the results, showing the highest exposure 

concentration for each substitute and the end use responsible. Complete results for each end use

and potential substitute can be found in Attachment 7-D.
135

7.1.3 Caveats and Limitations

This screening analysis of risks to the general population is a simple screening analysis that 

incorporates a variety of simplifying assumptions. The approach was intended to be 

conservative, i.e., to overestimate exposure point concentrations and potential human health risks. 

The major caveats and limitations of the analysis are listed below.

A. Estimating Releases. It was necessary to make assumptions to characterize releases, and 

the assumptions that would lead to the most conservative risk estimates were generally 

chosen.

C Within each end use grouping, there may have been several types of equipment 

with slightly varying charge sizes. It was assumed that the charge size of all 

equipment was equal to the largest charge of a piece of equipment in that category. 

In about half of the end uses, this assumption is true, but for the other half this is a 

very conservative assumption. For example, only 10 percent of commercial direct 

air conditioning equipment has the assumed charge size of 33 kg. The other 90 

percent has a charge of only 10.2 kg, and so the charge size (and thus releases) for 

90 percent of commercial direct air conditioning equipment has
136

EXHIBIT 7-1

RESULTS SUMMARY FOR HCFCs AND HFCs19

Substitute Highest Exposure 

Concentration/

RfC Ratioa

Highest 

Cancer 

Risk

Associated End Use/Site

HCFC-22 9.7 E-03 7.1 E-06 Central A/C and Home Heat Pumps/Factory

HCFC-123 1.0 E-02 4.3 E-06 High Pressure Centrifugal Chillers/Factory

HCFC-124 1.1 E-03 N/A Retail Food Stand Alone/Factory

HCFC-141

b

2.1 E-04 N/A Low Pressure Centrifugal Chillers/Factory

HCFC-142

b

3.2 E-03 N/A Refrigerators and Freezers/Factory

HFC-23 8.1 E-02 N/A Central A/C and Home Heat Pumps/Factory

HFC-125 4.9 E-02 N/A Central A/C and Home Heat Pumps/Factory

HFC-134 1.0 E-02 N/A High Pressure Centrifugal Chillers/Factory

HFC-134a 4.9 E-02 N/A Central A/C and Home Heat Pumps/Factory

HFC-143 1.4 E-03 N/A High Pressure Centrifugal Chillers/Factory

HFC-143a 6.9 E-03 N/A Central A/C and Home Heat Pumps/Factory

HFC-152a 9.5 E-03 N/A Window A/C Units/Salvage Yard

HFC-227ea 1.1 E-02 N/A Refrigerators and Freezers/Factory

N/A = Not Applicable

a

Some of the RfCs are Agency-verified while others are not. See Exhibit 3-1 for further information.

 

 

19

 Results are based on very conservative, screening-level assumptions and are not indicative of 

typical operating practices. See text and attachments for more detail.
137

been overestimated. See Attachment 7-E for a table detailing the charge sizes for 

the actual equipment versus the assumed charge size for each end use.

C The number of units manufactured per factory is not tracked by the Vintaging 

Model, so estimates for this analysis had to be developed. Data for production 

rates were based on estimated market shares for the largest manufacturer. For 

example, if there are three manufacturers of chillers, it was assumed, based on 

information from these manufacturers, that the largest manufacturer has 50 percent 

of the market share and of total annual production. It was also assumed that this 

manufacturer's total annual production was manufactured at one factory. These 

assumptions will, in many cases, result in an overestimation of the true production 

(and thus releases) at the actual largest factory.

C With one exception (low pressure chillers), it was assumed that every piece of 

equipment is charged (and recovered) at least once in the factory for run testing, 

although some manufacturers' quality control may include testing only a portion of 

all equipment sold.

C It was assumed that the equipment contains its full original charge at the point of 

service. In practice, this would rarely be the case since most servicing calls are 

made after leaking of refrigerant causes the equipment to malfunction. The effect 

of this assumption is to overstate releases, since the amount released is a percentage 

of the charge at the time of servicing.

C Disposal emissions also assume that a percentage of the total charge is vented at 

disposal, although this is rarely the case. As in servicing, a portion of the charge 

will have leaked before disposal.

C Reports from manufacturers of certain types of equipment, such as chillers, indicate 

that refrigerant leakage from operating equipment varies significantly depending 

on whether the equipment's level of maintenance is poor, average, or above 

average. Poor maintenance was assumed in all cases. An example of the amount 

of overestimation of releases which this approach could yield can be seen in 

chillers, of which only five percent to ten percent are generally poorly maintained.

C The amount of substitute used may not equal the amount of CFC used, due to the 

use of blends, increased efficiency in newly-built equipment, and the increased cost 

of the substitutes and the concomitant smaller equipment charge sizes. Also, some 

substitutes, such as HCFC-123, are already in use today and are known to be 

handled very differently from CFCs (i.e., they are handled more carefully). In the 

case of HCFC-123, a possible carcinogen, the actual risks will be smaller than those 

predicted.

B. Estimating Downwind Concentrations. Uncertainties associated with derivation of the 

dispersion factors are discussed by EPA (EPA 1990b). They include the following:

C EPA used a generic site location to model downwind concentrations. The 

meteorological conditions at this generic site were selected to cause conservative 

estimates of downwind concentrations.
138

C EPA's selection of model parameters characterizing the release (e.g., release height, 

size of the release facility) were based on professional judgment.

C Facility fenceline distance estimates (where exposure was simulated to occur) were 

also assumed by EPA. For some types of release sites, the model could not 

estimate concentrations at the assumed fenceline distance because in some cases 

the distances were as close as 10 meters. In these cases, the modeled 

concentrations at the exposure point were based on the highest concentrations 

predicted, but could be underestimates.

C The uncertainty faced in selecting dispersion factors to apply to each type of release 

site is discussed in detail in Attachment 7-C.

C. Screening Potential Risks. There are three important caveats associated with the risk 

calculations:

C Most of the calculations assume that an exposed individual lives and works in the 

same zone of concentration 24 hours per day, year-round, throughout a 70-year 

lifetime. Although this conservative assumption is often used in risk assessments, 

it is overly conservative for the HCFCs, which are scheduled to be phased out of 

production. To account for the phaseout in HCFC production, it was assumed that 

equipment manufacturing facilities would stop placing HCFC-22 and HCFC-123 

in equipment by 2010 and 2015, respectively. Therefore, when calculating cancer 

risk, the duration of exposure to factory releases of these substitutes was shortened 

to 18 and 23 years, respectively. A similar adjustment was not made in exposures 

to operating site releases because the phaseout will not preclude HCFCs from being 

used in existing equipment for the length of the equipment's lifetime. However, 

because the equipment is likely to replaced before 2062 C the end of the exposed 

individual's 70-year lifetime C cancer risks from releases of HCFC-22 and 

HCFC-123 from operating sites are overestimated in this analysis.

C Risks from exposure to operating site releases were based on the highest amount of 

substitute that would be released in any one year (i.e., the sum of releases from 

equipment operation, servicing, and either installation or disposal). Because 

installation and disposal each happen only once over the equipment's lifetime, and 

servicing typically occurs less frequently than once a year, exposures and risks 

from operating sites are overestimated.

7.1.4 Conclusions

Even employing conservative screening assumptions, EPA found that there are no end uses 

within the refrigeration or air conditioning sectors where the use of HFCs or HCFCs as substitutes 

for CFCs will result in exposure concentrations above the chemicals' health-based reference 

concentrations for non-cancer effects. Similarly, there are no areas for which predicted cancer 

risks would be above the upper-bound cancer risk level of concern, 10-5.
139

7.2 OTHER ALTERNATIVE REFRIGERANTS

This section discusses the following refrigerant substitutes: ammonia, butane, isobutane, 

propane, cyclopropane, perfluoropropane, and dimethyl ether (DME)20. After a background 

discussion, the approach for the analysis and the results are discussed.

7.2.1 Background

Many of these alternative refrigerants currently find wide use in industrial applications. 

Ammonia was one of the first refrigerants to gain acceptance, and is used almost exclusively in the 

meat packing, dairy, frozen juice, brewery, cold storage, and other food industries. The 

hydrocarbon refrigerants are used primarily in oil refineries and chemical plants, where they are 

frequently available as part of the process stream. The expanded use of many of the refrigerants 

in this section in other refrigeration and air conditioning equipment has been proposed, 

particularly as components in blends with the HFCs and HCFCs.

 

 

20 Several of these refrigerant substitutes are used in blends while others may be used in their pure 

form. 
140

Most industrial process refrigeration systems are designed by consulting firms that 

specialize in the field. The consultants typically work with the client to determine the exact 

specifications (cooling loads, for example), then design the system using off-the-shelf or speciallyfabricated components. Smaller, more standard designs, such as those for a cold storage 

warehouse, are more likely to use off-the-shelf components as these are cheaper and more readily 

available. The consultants sometimes supervise construction, installation, and start-up of the 

refrigeration system.

Compressors for large industrial process refrigeration systems are built by a handful of 

companies. Because they are large, complicated pieces of machinery, compressors are tested at 

the factory, but for safety purposes testing is not done with the refrigerant that will ultimately be 

used. For hydrocarbon refrigerants, run testing is typically done with dry air, and a correlation 

made with the refrigerant to determine the compressor's operating performance (Shephard 1992). 

Ammonia compressors are tested with air and a soap solution or tested under water to see if 

bubbles appear at joints. Ammonia package systems (those that have the evaporating and 

condensing units attached) are similarly tested with an air/soap solution, then charged with dry 

nitrogen before being shipped (Anderson 1992; Pillis 1992).

Industrial systems are erected in the field, leak tested again, then charged with the 

refrigerant. Care is taken during the charging operation to ensure that vapor concentrations are 

kept below hazardous levels. Ammonia systems usually have a charge size that makes them 

subject to OSHA PEL limits for ammonia (Anderson 1992), while ASHRAE standards for 

refrigeration systems recognize that worker exposure due to routine operating leakage from the 

system, or that occurs during servicing, should be kept below threshold levels. These codes are 

adopted into local and state building codes in most of the U.S. and are used as guidelines by the 

system designers21. In all cases, it is unlikely that emissions from a process refrigeration system 

operating on an industrial refrigerant would exceed those of a similar system operating on CFCs or 

HCFCs. 

7.2.2 Approach

This analysis of ammonia, butane, isobutane, propane, cyclopropane, perfluoropropane, 

and DME is a simple screening analysis to determine whether general population exposure is 

potentially of concern in specific end uses. The analysis used the fenceline exposure 

concentrations predicted above for HCFCs and HFCs and assumed that the fenceline 

concentrations of the alternative refrigerants noted above would be the same. This is a 

conservative approach because (1) the HCFC and HFC fenceline concentrations were calculated 

using conservative assumptions that are likely to overestimate exposure levels, and (2) releases of 

these alternative refrigerants are likely to be even lower because of the OSHA and ASHRAE 

standards to which their refrigerant uses are subject.

Conclusive data on the significance of factory releases were unavailable. Consequently, 

to be conservative in the analysis for these alternative refrigerants, factory releases were evaluated 

in addition to releases on-site during operation and servicing and those at disposal. The only

exception to this approach was for ammonia. Although compressors for large industrial process 

refrigeration systems are tested at the factory, for safety purposes this testing is not done with 

 

 

21 ASHRAE code 34-1992 classifies ammonia as a toxic and mildly flammable refrigerant and the 

hydrocarbons as highly flammable refrigerants.
141

ammonia. Similarly, charging of ammonia systems is typically performed at the operating site 

rather than the factory. Therefore, ammonia is unlikely to be released from a factory setting.

These fenceline concentrations were then compared to reference concentrations for each of 

the substitutes. From Chapter 3, the following reference concentrations were employed22:

 

 

22 Some of the RfCs are Agency-verified while others are not. See Exhibit 3-1 for further information.
142

Ammonia: 0.1 mg/m3

Perfluoroprop

ane: 4.5 mg/m3

Butane: 0.95 

mg/m3

Cyclop

ropane:

0.9 

mg/m3

Isobutane: 0.95 mg/m3

Dimethyl 

ether: 0.4 mg/m3

Propane: 0.9 mg/m3

7.2.3 Results

Exhibit 7-2 summarizes the results of the approach described in 7.2.2. For each end use, 

the highest exposure concentration (from Attachment 7-D) is shown. The location of this 

exposure (i.e., at the factory, on-site, or at the disposal site) is also reported. For the applicable 

refrigerants, the ratio of the concentration to the substitutes' reference concentrations is calculated. 

None of these ratios exceeded the health-based thresholds. 

Caveats and limitations associated with this analysis are the same as those discussed above 

for HCFCs and HFCs. In addition, there is considerable uncertainty associated with the 

health-based thresholds used for butane, propane, and perfluoropropane, which were extrapolated 

from workplace exposure limits rather than calculated from laboratory studies. EPA believes that 

the exposure limits used in this analysis are conservative.

Given the conservative nature of the release estimates and interim health-based levels used 

in this analysis, EPA concludes that general population exposure is not of concern for these seven 

substitutes.

7.3 CHLORINE

Chlorine has been proposed as a Class I substitute refrigerant for use in chlorine 

liquification, a processing step in the manufacture of the chemical. When chilled below its 

boiling point, chlorine can be stored as a liquid at atmospheric pressure, a method that for safety 

reasons is much preferred to storing the chemical as a pressurized gas at ambient temperatures. 

Compatibility of the refrigerant with liquid chlorine is critical because of chlorine's high reactivity; 

CFC-12 is widely used because it is nonreactive.
143

EXHIBIT 7-2: RESULTS SUMMARY FOR OTHER ALTERNATIVE REFRIGERANTSa

a Releases are based on the assumption that the refrigerant is not recycled when the equipment is serviced or dismantled for disposal. This does not reflect 

common operating practices and therefore overstates true risk.
144

Chlorine refrigeration systems generally do not exchange chlorine with the process stream. 

However, the system would be placed so that any leakage or losses of chlorine would be contained 

and neutralized by the process safety mechanisms. Charge sizes in the refrigeration system 

would probably be less than 1000 kg, as compared to a bulk storage container havingseveral 

hundred times that capacity. Chlorine emissions from the refrigeration system are likely to be 

dwarfed by those emanating from the process and storage systems, which are already kept small 

for reasons of worker safety.

Based on these considerations, EPA does not believe that the use of chlorine as a 

refrigerant in this limited application C the manufacture of chlorine C poses significant 

incremental risk to the general population.

7.4 LITHIUM BROMIDE AND AMMONIA IN ABSORPTION SYSTEMS

Lithium bromide is used in commercial absorption systems, where it serves as an 

absorbent. Such systems operate at very low pressure to allow water to act as a refrigerant. The 

lithium bromide is in the form of an ionic salt having a negligible vapor pressure, so there is no 

possibility of a gaseous release in other than catastrophic circumstances. Lithium is also a 

relatively nontoxic, nonflammable, nonexplosive, chemically stable chemical, and poses little 

incremental risk to the general population.

Absorption refrigeration systems employing a mixture of ammonia and water have been 

used for many years. Small refrigeration units are popular in recreational vehicles and hotel 

refrigerators as they need no electrically-driven mechanical pump. Domestic absorption type 

systems use hydrogen to maintain a system pressure high enough to allow the ammonia refrigerant 

to evaporate at low pressure and temperature (and condense at room temperature), and are 

ruggedly constructed; the absorption mechanism itself is a sealed unit, which usually needs no 

servicing over its operating life. Commercial ammonia absorption systems are used for air 

conditioning comfort cooling, particularly in instances where waste heat is available. These 

produce chilled water, which is circulated to the space being cooled. The same standards and 

guidelines that apply to ammonia vapor compression equipment also apply to commercial 

ammonia absorption systems. In a well-maintained system, it is unlikely that ammonia emissions 

would pose a problem.
145

CHAPTER 7 REFERENCES

Anderson, Kent. 1992. May 5. Phone conversation between Mark Radka, ICF Incorporated, 

and Kent Anderson, Chairman of the International Institute of Ammonia Refrigeration.

Aucott, Michael. 1990. December 14. Feasibility of CFC-12 Reclamation from Salvaged 

Vehicles. Department of Environmental Protection, Division of Solid Waste 

Management, State of New Jersey.

Pillis, J. 1992. May 5. Phone conversation between Mark Radka, ICF Incorporated, and J. 

Pillis, Chief Engineer, The Frick Company.

Shephard, James. 1992. May 4. Phone conversation between Mark Radka, ICF Incorporated, 

and James Shephard, Vice President of Engineering, Lewis Energy Systems, and Chair of 

the ASHRAE Technical Committee on Custom Refrigeration Systems.

U.S. EPA. 1992. Regulatory Impact Analysis: Compliance with Section 604 of the Clean Air 

Act for the Phaseout of Ozone Depleting Chemicals. Office of Air and Radiation. March 

12, 1992.

U.S. EPA. 1990a. External Review Draft, Hydrofluorocarbons and Hydrochlorofluorocarbons, 

Interim Report. Office of Toxic Substances. November, 1990.

U.S. EPA. 1990b. Potential Ambient Inhalation Exposures for Chlorofluorocarbon Substitutes. 

Office of Toxic Substances. Exposure Evaluation Division, Exposure Assessment 

Branch. November 7, 1990.

U.S. EPA. 1990c. Revised Draft: Occupational Exposure and Environmental Release Data for 

Chlorofluorocarbons (CFCs) and Their Substitutes. Office of Toxic Substances.
ATTACHMENT 7-A

DETAILED CATEGORIZATION OF REFRIGERATION END USES

AND EQUIPMENT TYPES

("Near-Term" Substitutes In Italics) 

1. Retail Food - Parallel Systems

 CFC-12 (medium temperature) HFC-134a 

HCFC-22 

HCFC-22/HFC-152a/HCFC-124

HFC-125/HFC-143a/HFC-134a

ammonia

 CFC-502 (low temperature) HFC-125 

HFC-143a

HCFC-22 

HCFC-22/propane/perfluoropropane

HCFC-22/propane/HFC-125

 HCFC-22 (medium and low temperature) HFC-125

HFC-134a

HFC-23/HFC-134a

HFC-125/HFC-143a

HCFC-22/propane/HFC-125

2. Retail Food - Stand Alone Systems

 CFC-12 (medium temperature) HFC-134a 

HCFC-22 

HCFC-22/HFC-152a/HCFC-124

HFC-125/HFC-143a/HFC-134a

ammonia

 CFC-502 (low temperature) HFC-125 

HFC-143a

HCFC-22 

HCFC-22/propane/perfluoropropane

HCFC-22/propane/HFC-125

3. Cold Storage Warehouses

 CFC-12 (medium/high temperature) HFC-134a 

HFC-152a 

HCFC-22

HCFC-22/HFC-152a/HCFC-124

ammonia
turbochill

 HCFC-22 (medium/high temperature) HFC-134a

HFC-152a

HFC-23/HFC-134a

HCFC-22/HFC-152a/HCFC-124

ammonia

turbochill

 CFC-502 (low temperature) HFC-125 

HCFC-22

HCFC-22/propane/perfluoropropane 

ammonia

4. Reciprocating Chillersa

 CFC-12 HFC-134a 

HFC-152a 

HCFC-22

HCFC-123

HFC-125/HFC-143a/HFC-134a

 HCFC-22 HFC-134a 

HFC-23/HFC-134a

HFC-125/HFC-143a

HCFC-22/propane/HFC-125

ammonia

5. Screw Chillersa

 HCFC-22 HFC-134a

HFC-23/HFC-134a

HCFC-22/propane/HFC-125

ammonia

6. Centrifugal Low Pressure Chillersa

 CFC-11 HFC-134a

HCFC-22

HCFC-123

HCFC-141b

 

 

a

Includes three maintenance profiles: poor, average, above average.
148

lithium bromide/water absorption

ammonia/water absorption
149

7. Centrifugal High Pressure Chillersa

 CFC-12 HFC-134a

HCFC-22

HCFC-123

lithium bromide/water absorption

 CFC-114 HCFC-124

HCFC-142b

R200b

R200c

R200d

R200e

R200f

R200g

R200i

R200j

 CFC-500 HFC-134a

HCFC-22/HFC-152a/HCFC-124 

HFC-134a/HFC-152a

ammonia

 HCFC-22 HFC-134a 

ammonia

8. Industrial Process Refrigeration - Low Pressure Systems

 Centrifugal Package Systems (CFC-11) HCFC-123

HCFC-141b

 Centrifugal Built-Up Systems (CFC-11) HCFC-123

HCFC-141b
150

9. Industrial Process Refrigeration - High Pressure Package Systems

 CFC-12 Reciprocating HFC-134a 

HFC-143a

 HCFC-22 Reciprocating HFC-152a

HCFC-22 

 CFC-502 Reciprocatinga HFC-23/HFC-134a

HFC-125/HFC-143a

HCFC-22/HFC-152a/HCFC-124

HFC-125/HFC-143a/HFC-134a

HCFC-22/propane/HFC-125

propane 

butane 

ammonia 

10.Industrial Process Refrigeration - High Pressure Built-Up Systems

 

 

a This end use includes extra large ice makers.
151

 CFC-12 Reciprocating HFC-134a 

HFC-152a

 HCFC-22 Centrifugal HCFC-22

HFC-23/HFC-134a

 CFC-500 Centrifugal HFC-125/HFC-143a

HCFC-22/HFC-152a/HCFC-124

 CFC-12 Reciprocating HFC-125/HFC-143a/HFC-134a

HCFC-22/propane/HFC-125

 HCFC-22 Reciprocating propane 

butane 

ammonia 

chlorine

11.Ice Skating Rinks

 CFC-12 HFC-134a

HFC-152a

 HCFC-22 HCFC-22

HFC-23/HFC-134a

 CFC-502 HCFC-22/HFC-152a/HCFC-124

ammonia

12.Medium Ice Makers

 CFC-12 HCFC-22

HFC-134a

HFC-152a

HCFC-22/HFC-152a/HCFC-124

ammonia

13.Large Ice Makers

 CFC-12 HCFC-22

HFC-134a

HFC-152a

HCFC-22/HFC-152a/HCFC-124

ammonia

14.Refrigerated Transport Units

 CFC-12 HFC-134a

HCFC-22

HCFC-22/HFC-152a/HCFC-124

HFC-125/HFC-143a/HFC-134a
152

 CFC-500 HFC-134a

HCFC-22

HCFC-22/HFC-152a/HCFC-124 

HCFC-22/propane/HFC-125

 CFC-502 HFC-125

HFC-134a

HCFC-22

HCFC-22/propane/HFC-125

15.Window Air Conditioners

 HCFC-22 HFC-125

HFC-134a 

HFC-23/HFC-134a

HFC-125/HFC-143a

16.Central Air Conditioners and Home Heat Pumps

 Package Terminal Air HFC-125

Conditioners (HCFC-22) HFC-134a

HFC-23/HFC-134a

 Residential Unitary Air HFC-125/HFC-143a

Conditioners (HCFC-22) HFC-125/HFC-143a/HFC-134a

HCFC-22/propane/HFC-125

 Unitary Heat Pumps (HCFC-22)

 Water Source Heat Pumps (HCFC-22)
153

17.Commercial Direct Expansion Air Conditioning Systems

 Small Commercial Air HFC-125 

Conditioners (HCFC-22) HFC-134a

HFC-23/HFC-134a

 Large Commercial Air HFC-125/HFC-143a

Conditioners (HCFC-22)

18.Refrigerators and Freezers

 Refrigerators (CFC-12) HFC-134a 

HFC-152a

 Freezers (CFC-12) HCFC-22

R200b

 HCFC-22/HFC-152a/HCFC-124 

HCFC-22/HCFC-142b 

ammonia/water absorption

19.Other Refrigerated Appliances

 Dehumidifiers (CFC-12) HFC-134a 

HFC-152a 

 Vending Machines (CFC-12) HCFC-22/HFC-152a/HCFC-124

 Small Ice Makers (CFC-12) HCFC-22

 Water Coolers (CFC-12)

 Small Ice Makers (CFC-502) HCFC-22

20.Mobile Air Conditioners

 CFC-12 HFC-134a 

HCFC-22/HFC-152a/HCFC-124
ATTACHMENT 7-B:

ASSUMPTIONS FOR AMBIENT AIR RELEASE CALCULATIONSa

RETAIL FOOD SYSTEMS

Type/Site of Release Parallel Systems Stand-Alone 

Systems

MANUFACTURING RELEASES - FACTORY

No. of units manufactured per plant per year 2,900 30,000b

Release per unit manufactured (kg) 6.0 2.0

ON-SITE RELEASES

No. of units per site 1 2

Release per unit installed (kg) 93 3.0

Release per unit serviced (kg)

without recycling 7.7 20

with recycling 3.1 1.2

recycling efficiency 99% 99%

Release per unit operating (kg/yr) 130 1.9

Release per unit disposed (kg)

without recycling 470 19

with recycling 4.7 0.19

recycling efficiency 99% 99%

 

 

a

Data from ICF's Vintaging Model and supplemental analysis performed by ICF.

 

b

The largest manufacturer of retail food refrigeration equipment (Hussman) manufactures approximately 30,000 units per year in

one factory.
155

COLD STORAGE WAREHOUSES

Type/Site of Release Cold Storage 

Warehouses

MANUFACTURING RELEASES - FACTORY

No. of units manufactured per plant per year 

57a

Release per unit manufactured (kg) 15

ON-SITE RELEASES

No. of units per site 

4

b

Release per unit installed (kg) 3.5

Release per unit serviced (kg)

without recycling 52

with recycling 5.0

recycling efficiency 99%

Release per unit operating (kg/yr) 50

Release per unit disposed (kg)

without recycling 250

with recycling 2.5

recycling efficiency 99%

 

 

a

Based on approximately 43,140,000 cubic feet of new cold storage warehouse space per year, an average warehouse volume of 

1,000,000 cubic feet, and an estimated four refrigeration units per warehouse, 173 units of equipment are produced per year. One 

manufacturer estimates that there are 15 manufacturers of cold storage refrigeration equipment, and another reports that there are three. 

We assume that there are three manufacturers, each producing 57 units per year.

 

b

Assumes that a typical warehouse has 1,000,000 cubic feet of refrigerated space, requiring a total size of 1000 kg that is provided 

by four units (250 kg each).
156

CHILLERS

Type/Site of Release

Reciprocating 

Chillers

Screw 

Chillers

Centrifugal Chillers

Low 

Pressur

e

High 

Pressure

MANUFACTURING RELEASES -

FACTORY

No. of units manufactured per plant per 

year

3,000a 230b1,200c 370c

Release per unit manufactured (kg) 5.0 5.1 16d52

ON-SITE RELEASES

No. of units per site 1 1 1 1

Release per unit installed (kg) 1.1 1.1 2.0 2.0

Release per unit serviced (kg)

without recycling 5.1e 11e 28e 37e

with recycling 0.15 0.21 1.3 1.4

recycling efficiency 99% 99% 99% 99%

Release per unit operating (kg/yr) 23f 54f 110f 260f

Release per unit disposed (kg)

without recycling 73 230 450 900

with recycling 0.73 2.3 4.5 9.0

recycling efficiency 99% 99% 99% 99%

 

 

a

This estimate is based on three chiller manufacturers (Trane, York, Carrier) producing 90 percent of new chillers in approximately 

equal proportion.

 

b

Assumes that all screw chillers are manufactured at the same factory.

 

c

Assumes that three manufacturers (Trane, York, Carrier) produce nearly all chillers, and that one manufacturer has 50 percent of 

the market share.

 

d

According to Trane, only 20% or less of the units manufactured are charged at the factory.

 

e

The more frequently a chiller is serviced, the greater its servicing related emissions will be. Above average maintenance is

assumed for the purpose of estimating servicing releases.

 

f

Reports from chiller manufacturers indicate that refrigerant leakage from operating equipment varies significantly depending on 

whether the chiller's level of maintenance is poor, average, or above average. Poor maintenance is assumed for the purpose of estimating 

operating releases.
157

INDUSTRIAL PROCESS REFRIGERATION

Type/Site of Release

Low 

Pressure

High 

Pressure 

Package

High 

Pressure 

Built Up

Ice 

Skating 

Rinks

Medium 

Ice 

Makers

Large Ice 

Makers

MANUFACTURING RELEASES - FACTORY

No. of units manufactured per plant per year 32a 130a 130a 41a50,000b 

8.0c

Release per unit manufactured (kg) 24 13 190 1.0 0.19 2.1

ON-SITE RELEASES

No. of units per site 1 1 1 1 1 1

Release per unit installed (kg) 11 11 11 11 0 0.68

Release per unit serviced (kg)

without recycling 140 19 910 28 2.3 34

with recycling 15 2.8 10 1.3 0.05 0.68

recycling efficiency 99% 99% 99% 99% 99% 99%

Release per unit operating (kg/yr) 68 27 1,800 57 0.15 2.2

Release per unit disposed (kg)

without recycling 680 180 9,100 1,400 2.3 34

with recycling 6.8 1.8 91 14 0.02 0.34

recycling efficiency 99% 99% 99% 99% 99% 99%

 

 

a

Assumes that three manufacturers (Trane, York, Carrier) produce nearly all of the equipment in this table (excluding ice makers) and that one manufacturer has 50 percent of the market 

share.

 

b

There are ten manufacturers of medium size ice makers. Assumes that the largest manufacturer has one third of total annual production.

 

c

Assumes a single manufacturer of large ice makers.
158

TRANSPORT REFRIGERATION

Type/Site of Release

Transport 

Refrigeration

MANUFACTURING RELEASES - FACTORY

No. of units manufactured per plant per year 

14,100a

Release per unit manufactured (kg) 1.0

ON-SITE RELEASES

No. of units per site 1

Release per unit installed (kg) 0.25

Release per unit serviced (kg)

without recycling 2.0

with recycling 0.02

recycling efficiency 99%

Release per unit operating (kg/yr) 0.20

Release per unit disposed (kg)

without recycling 8.1

with recycling 0.08

recycling efficiency 99%

 

 

a

Based on Carrier Transicold and Thermo King, each with one manufacturing facility, equally sharing an estimated 90 percent of 

1992 production.
159

HOUSEHOLD AND OTHER REFRIGERATED APPLIANCES

Type/Site of Release

Window 

A/C Units

Central A/C 

& Home 

Heat Pumps

Commercial 

Direct 

Expansion 

A/C

MANUFACTURING RELEASES - FACTORY

No. of units manufactured per plant per year 300,000a 400,000a 38,600b

Release per unit manufactured (kg) 0.05 0.23 0.33

ON-SITE RELEASES

No. of units per site 1 1 1

Release per unit installed (kg) 0 0 11

Release per unit serviced (kg)

without recycling 1.8 3.8 33

with recycling 0.04 0.08 0.66

recycling efficiency 99% 99% 99%

Release per unit operating (kg/yr) 0.38 0.80 6.9

Release per unit disposed (kg)

without recycling NA 3.8 33

with recycling NA 0.04 0.33

recycling efficiency NA 99% 99%

DISPOSAL RELEASES -

RECYCLING/SALVAGING CENTER

No. of units processed per site per year 26,000c NA NA

Release per unit processed (kg)

without recycling 1.8 NA NA

with recycling 0.02 NA NA

recycling efficiency 99% NA NA

NA = Not applicable

 

 

a

There are 40 manufacturers of home air conditioning units. We assume the largest manufacturer has 10 percent of the total 

market share.

 

b

Assumes five manufacturers of commercial air conditioning equipment with an equal market share for each.

 

c

Actual processing data for Appliances Recycling Centers of America (ARCA) facility in Minneapolis, MN.
160

HOUSEHOLD AND OTHER REFRIGERATED APPLIANCES

Type/Site of Release Refrigerator

s and 

Freezers

Other 

Refrigerated 

Appliances

MANUFACTURING RELEASES - FACTORY

No. of units manufactured per plant per year 750,000a170,000b

Release per unit manufactured (kg) 0.04 0.04

ON-SITE RELEASES

No. of units per site 1 1

Release per unit installed (kg) 0 0

Release per unit serviced (kg)

without recycling 0.41 0.50

with recycling 0.02 0.03

recycling efficiency 95% 95%

Release per unit operating (kg/yr) 

0.40c

 

0.50c

Release per unit disposed (kg)

without recycling NA 0.50

with recycling NA 0.03

recycling efficiency NA 95%

DISPOSAL RELEASES - RECYCLING/SALVAGING 

CENTER

No. of units processed per site per year 17,000d2,400e

Release per unit processed (kg)

without recycling 0.40 0.41

with recycling 0.02 0.02

recycling efficiency 95% 95%

NA = Not applicable

 

 

a

There are 25 manufacturers of domestic refrigerators and freezers. We assume the largest manufacturer has 10 percent of the total 

market share.

 

b

There are 25 manufacturers of other refrigerated appliances. Assumes that the largest manufacturer has 10 percent of total market 

share.

 

c

Refrigerators and freezers and other refrigerated appliances have hermetically sealed systems and rarely leak. If they do leak, 

however, they are likely to lose their entire charge--the value represented in this table.

 

d

Actual processing data for Appliances Recycling Centers of America (ARCA) facility in Minneapolis, MN.

 

e

Data for dehumidifiers only.
161

MOBILE AIR CONDITIONERS

Type/Site of Release

Mobile Air 

Conditioners

MANUFACTURING RELEASES - FACTORY

No. of units manufactured per plant per year 325,000a

Release per unit manufactured (kg) 0.11

INSTALLATION RELEASES - SERVICE STATION

No. of units per site 

63b

Release per unit installed (kg) 0.11

SERVICING RELEASES - SERVICE STATION

No. of units serviced per site per year 

165c

Release per unit serviced (kg)

without recycling 1.2

with recycling 0.06

recycling efficiency 95%

DISPOSAL RELEASES - RECYCLING/SALVAGING CENTER

No. of units processed per site per year 

4,250d

Release per unit processed (kg)

without recycling 1.2

with recycling 0.06

recycling efficiency 95%

 

 

a

The Motor Vehicle Manufacturers Association (MVMA) reports that the capacity of one of the largest auto manufacturing plants 

(Honda Civic plant in Marysville, Ohio) is 360,000 cars per year. Eighty five percent of new cars are assumed to have factory-installed 

MACs.

 

b Mobile air conditioners installed after car purchase at the customer's request (referred to as after-market MACs) would experience 

leak testing and fill-related emissions at the installation site instead of the auto factory. We assume that all dealerships that service MACs 

also install MACs (23,550 dealerships [MACs RIA]).

 

c

This is the numbers of MACs typically serviced in a large shop (MACs RIA)

 

d

Assumes that 17 MACs are processed per day, 250 days per year.


ATTACHMENT 7-C

METHODOLOGY FOR ESTIMATING GENERAL POPULATION EXPOSURES TO 

AMBIENT AIR RELEASES OF SUBSTITUTES FOR CLASS I SUBSTANCES

FOR SNAP RISK SCREENS

The approach used to estimate general population exposures to ambient air releases of 

substitutes for Class I ozone-depleting substances (ODSs) for the SNAP risk screens is patterned 

after the approach EPA used previously (EPA 1990a) for the interim report on HFCs and HCFCs 

(EPA 1990b). The sections below summarize EPA's earlier approach and discuss how it was 

applied to the SNAP risk screens. 

SUMMARY OF EPA'S EARLIER APPROACH FOR ESTIMATING GENERAL 

POPULATION EXPOSURES

EPA's approach for estimating general population exposures for the interim report on HFCs 

and HCFCs is summarized in the two documents referred to above. EPA used information 

developed by PEI (EPA 1990c), combined with engineering judgment, to develop estimates of 

ambient air releases from each of the activities shown in Exhibit 7-C-1. EPA then used the 

Industrial Source Complex Long Term (ISCLT) Dispersion Model to estimate ambient air 

concentrations at an assumed exposure point.

The ISCLT model is a steady-state Gaussian plume model which can be used to assess 

pollutant concentrations from a wide variety of sources associated with an industrial source 

complex. Additional information on the model can be found in EPA's Industrial Source Complex 

(ISC) Dispersion Model User's Guide (EPA 1986) and addendum (EPA 1987). The model has 

not been through Science Advisory Board or formal external peer review, but it has been reviewed 

and recommended for general use by EPA's Office of Air Quality Planning and Standards for 

applications similar to this. 

To run the ISCLT model, it was necessary for EPA to develop inputs for source characteristics 

and meteorological factors.

! EPA used engineering judgment to develop assumptions about the characteristics of the 

facilities (e.g., stack height, surface area) from which the ODSs are released.

! EPA used meteorological conditions for a "generic" site, which was selected based on an 

analysis of maximum exposed individual concentrations calculated for an identical release 

from each of 392 sites across the U.S. The meteorological conditions at this generic site 

were known to cause conservative estimates of exposure point concentrations.

EPA then used the ISCLT model outputs to estimate concentrations at the fenceline of the release 

site. Distances to the fenceline varied depending on the type of release site, and were based on 

professional judgment. EPA points out that for some types of release sites, the model was unable 

to predict concentrations as close as the assumed fenceline distance. In these cases, the exposure 

estimates were based on the highest concentrations predicted by the model.

EPA documents several areas of uncertainty associated with the release, concentration, and 

exposure estimates; these are not repeated here.
APPLYING EPA'S EARLIER APPROACH TO THE SNAP RISK SCREENS

For the SNAP risk screens, general population exposures to ambient air releases of Class I 

substances were estimated using three basic steps:

(1) The first step was to update the ambient air 

release information presented in the EPA 

report (EPA 1990c) using more recent data. 

Conservative estimates were made of annual 

ambient air releases of ODS substitutes from 

different types of facilities (e.g., chemical 

manufacturing plants, factories that produce 

equipment containing the substitutes, sites at 

which the substitutes are used, service 

stations, centralized recycling or disposal 

facilities);

(2) Each type of release site was "matched up" 

with one that was modeled earlier by EPA; 

and

(3) The results of the previous ISCLT runs were 

used to determine the relationship between 

the release rate and exposure point 

concentration for each type of release site; 

that factor was then applied to the revised 

release estimates to derive a new fenceline 

concentration.

Steps (1) and (3) were straightforward. The approach used to calculate releases from different 

types of facilities (Step 1) is described in the section documenting the general population exposure 

analysis for each use sector. To determine the relationship between releases and fenceline 

concentrations (Step 3), EPA's contractor for the earlier analysis (Versar) provided a table 

identifying the "normalized maximum concentration at the fenceline, g/m3" for each of the runs 

conducted for the interim report. These normalized maximum concentrations, shown in Exhibit 

7-C-1, are the maximum fenceline concentrations that result from the release of one gram per 

second (g/sec) of ODS from a source. Using them is simply a matter of converting estimated 

annual releases to g/sec and multiplying them by the normalized concentration, yielding maximum 

fenceline concentrations in g/m3.

Some difficulties were encountered in the second step, however, which add to the uncertainties 

associated with the ambient air modeling. These difficulties arise from two factors, discussed 

below.

! First, it was sometimes difficult to identify the type of facility associated with each 

normalized concentration listed in Exhibit 7-C-1. This is because the normalized 

concentrations are presented by type of activity (e.g., manufacturing, servicing) rather than 

type of source (e.g., factory, operating site, service station). To cross-walk the normalized 

concentrations provided in Exhibit 7-C-1 with different types of release sites for the SNAP 
4

risk screens, EPA examined the model input parameters and patterns among the normalized 

concentrations themselves. EPA believes that the types of release sites associated with 

each normalized concentration were identified accurately using this approach.

! Second, and more importantly, the SNAP risk screens cover certain end uses that were not 

covered in the general population exposure portion of the interim analysis because the end 

uses were believed to consume relatively small amounts of ODSs. Because the SNAP risk 

screens attempt to cover all end uses, normalized concentrations were needed for source 

types not previously modeled. Professional judgment was used to select which normalized 

concentrations (among those listed in Exhibit 7-C-1) to use for source types that were not 

modeled earlier. 

Exhibit 7-C-2 lists the normalized concentrations that EPA used for each source type in the 

SNAP analyses of general population exposure to ambient air releases.
5

EXHIBIT 7-C-1

NORMALIZED FENCELINE CONCENTRATIONS (EPA/VERSAR)

SECTOR ACTIVITY TYPE OF 

RELEASE

NORMALIZED 

MAX. 

FENCELINE 

CONC. (g/m3)

CHEMICAL 

MANUFACTURING

Manufacture of CFCs Stack 8.9

Manufacture of CFCs Area 60.4

REFRIGERATION Retail Food: Manuf./Install. Volume 166.3

Retail Food: Servicing Volume 864.8

CSW: Manuf./Install. Volume 102.5

CSW: Servicing Volume 102.5

Chillers: Manuf./Install. Volume 166.3

Chillers: Servicing Volume 40.7

Ice Makers: Manuf. Volume 166.3

Ice Makers: Servicing Volume 864.8

Ice Skate Rinks: Manuf. Volume 254.8

Ice Skate Rinks: Servicing Volume 254.8

MACs: Manuf. Volume 58.8

MACs: Servicing Volume 864.8

Chem. Proc. & Refineries: 

Manuf.

Area 56.7

Chem. Proc. & Refin.: Servicing Area 56.7

FOAM BLOWING Foam Blowing: Rigid & Flexible Stack 6.2

Foam Blowing: Rigid & Flexible Volume 62.4

SOLVENTS PC Board Cleaning Stack 9.6a

PC Board Cleaning Volume 166.3

Other Electronics Cleaning Stack 9.6a

Other Electronics Cleaning Volume 472.7

Metal Cleaning Stack 9.6a

Metal Cleaning Volume 166.3

STERILIZATION Sterilization Volume 40.7

a Normalized maximum concentrations for stack releases for the solvents sector were not provided 

by Versar. These values were back-calculated based on the releases and fenceline concentrations 

provided in the earlier EPA reports.
6

EXHIBIT 7-C-2

NORMALIZED MAXIMUM CONCENTRATIONS (g/m3) APPLIED TO DIFFERENT 

TYPES OF RELEASE SITES FOR SNAP RISK SCREENS

SECTOR END USE FACTORY 

RELEASE

S

OPERATING 

SITE 

RELEASES

SERVICE 

STATION 

RELEASE

S

DISPOSAL 

SITE 

RELEASES

b

CHEMICAL 

MANUFACTURE

Manufacture 

of CFCs

Stack: 8.9

Area: 60.4

 NA NA NA

REFRIGERATION Retail Food 166.3 864.8 NA NA

CSW 166.3 102.5 NA NA

Chillers 166.3 40.7 NA NA

Ice Makers 166.3 864.8 NA NA

Ice Rinks 166.3 254.8 NA NA

MACs 58.8 NA 864.8 56.7

ChProc & 

Ref

166.3 56.7 NA NA

Transport 

Ref

166.3 864.8 NA NA

Home 

Appliances

166.3 864.8 NA 254.8

Commercial 

A/C

166.3 254.8 NA NA

FOAM BLOWING Flexible 

Foam

 6.2 NA NA NA

Other End 

Uses

 62 NA NA NA

SOLVENT 

CLEANING

Cleaner 

Formulation

Stack: 8.9

Area: 60.4

 NA NA NA

PC Board 

Cleaning

 NA Stack: 9.6

Volume: 

166.3

 NA NA

Other 

Electron. 

Cleaning

 NA Stack: 9.6

Volume: 

472.7

 NA NA

Metal 

Cleaning

 NA Stack: 9.6

Volume: 

166.3

 NA NA

STERILIZATION Sterilization NA 40.7 NA NA

AEROSOLS Propellants 166.3 NA NA NA

Solvents 166.3 472.7 NA NA

HALONS Processing 

and 

Equipment

173 NA NA NA

ADHESIVES, 

COATINGS, AND 

INKS

All End Uses 166.3 166.3 NA NA
7

a

Entries in bold were developed for the SNAP risk screens based on a review of EPA and Versar 

documents; those not in bold were taken directly from Versar (see Exhibit 7-C-1).

b Applies to cases in which equipment is transported to a centralized location (e.g., recycling center or 

salvaging yard) before the ODS substitute is removed.
8

REFERENCES FOR ATTACHMENT 7-C

U.S. EPA. 1990a. Potential Ambient Inhalation Exposures for Chlorofluorocarbon Substitutes. 

Office of Toxic Substances, Exposure Evaluation Division, Exposure Assessment Branch. 

November 7, 1990.

U.S. EPA. 1990b. External Review Draft, Hydrofluorocarbons and Hydrochlorofluorocarbons, 

Interim Report. Office of Toxic Substances. November, 1990.

U.S. EPA. 1990c. Revised Draft: Occupational Exposure and Environmental Release Data for 

Chlorofluorocarbons (CFCs) and Their Substitutes. Office of Toxic Substances.

U.S. EPA. 1986. Industrial Source Complex (ISC) Dispersion Model User's Guide, Second Edition, 

Volumes 1 and 2. Publication Nos. EPA-450/4-86-005a, and -005b. U.S. Environmental 

Protection Agency, Research Triangle Park, NC. (NTIS PB86 234259 and PB86 234267).

U.S. EPA. 1987. Industrial Source Complex (ISC) Dispersion Model. Addendum to the User's 

Guide. U.S. Environmental Protection Agency, Research 

Triangle Park, NC.
9

ATTACHMENT 7-D

NOTE

The disposal scenario for household and other refrigerated appliances included emissions from the 

refrigerators and freezers, dehumidifiers (part of the "other refrigerated appliances" category), and 

window air conditioners sectors. Since all three kinds of equipment could conceivably be disposed of at 

the same salvage location, for the purposes of maintaining the conservative nature of this analysis, ratios 

should be summed for any substitutes that are common across these sectors. The resulting ratios are:

Substitute Ratio w/Recycling Ratio w/o 

Recycling Cancer Risk

HCFC-22 9.7E-05 N/A

 3.8E-08

HCFC-124 2.2E-06 N/A

 N/A

HFC-134a 4.9E-04 4.4E-02

 N/A

HFC-152a 1.2E-04 1.1E-02

 N/A

None of the resulting summed ratios are high enough to be considered of concern.
10

ATTACHMENT 7-E

Percent of Equipment with Assumed Charge Size

END USE Charge Size

(Kgs)

Percent of

Total in End

Use Category

Comments

Retail Food - Parallel 466 100

Retail Food - Stand alone 19 50 other 50% are 10 kg

Cold Storage Warehouses 250 100

Reciprocating Chillers 73 100

Screw Chillers 230 100

Centrifugal Chillers - LP 450 100

Centrifugal Chillers - HP 900 70 25% are 820 kg,

5% are 540 kg

Industrial Process - LP 680 100

Industrial Process

High Pressure Package

180 89 11% are 145 kg

Industrial Process

High Pressure Built Up

9100 7 58% are 4550 kg

6% are 2200 kg

29% are 1800 kg

Ice Skating Rinks 1360 52 48% are approx. 350 kg

Medium Ice Makers 2.3 100

Large Ice Makers 34.1 100

Transport Refrigeration 8.1 100

Window A/C 1.8 100

Central A/C and Heat Pumps 3.8 20 75% are approx. 3 kg

5% are 0.7 kg

Commercial Direct A/C 33 10 90% are 10.2 kg

Refrigerators and Freezers 0.4 8 92% are between 0.19 kg 

and 0.33 kg

Other Refrigerated Appliances 0.5 10 42% are 0.4 kg

14% are 0.2 kg

34% are 0.1 kg

Mobile Air Conditioners 1.2 40 60% ar 0.88 kg
8. VOLATILE ORGANIC COMPOUND ANALYSIS

This chapter examines volatile organic compound (VOC) emissions from substitutes to Class I 

ozone-depleting substances (ODSs) that may be used for some end uses within the refrigeration and air 

conditioning sector. The VOCs of concern for this sector are the hydrocarbons. VOCs are important to 

investigate as they can lead to the formation of ground-level ozone and, thus, degradation of ambient air 

quality and adverse health effects.

This is a screening-level assessment where overly conservative, worst-case scenarios are presented. 

The general approach used in this analysis was to compare total nationwide potential emissions from 

sources using VOC substitutes in the refrigeration and air conditioning industry with total VOCs from all 

other sources (e.g., other industries, mobile sources, and biogenic sources). Next, a hypothetical sample 

area (the Trane facility in the city of Indianapolis) was chosen to demonstrate a worst-case air emission 

situation. The estimated potential emissions from a facility that had switched to VOCs were added to a 

per-capita emissions amount (to account for releases from refrigeration and air conditioning units 

already in operation) and compared with the total VOC emissions from all other sources. 

These comparisons give an indication of the potential impact of Class I substitutes in this sector on 

VOC emissions and the resulting formation of ground-level ozone.

8.1VOC EMISSIONS FROM SUBSTITUTES TO CLASS I ODSs

To estimate VOC releases from ODS substitutes in the refrigerant and air conditioning industry, the 

estimated 1992 nationwide release of ODSs were examined in all refrigerant and air conditioning end 

uses for which hydrocarbons have been suggested as substitutes. The year 1992 was chosen based on 

the assumption that the effects of the CAA phaseout mandate would not begin until after 1991 or 1992.

The release estimates are from the Vintaging Model.w For the purposes of this screening-level 

analysis, it was assumed that hydrocarbons would capture 100 percent of the market share for substitutes 

to Class I ODSs in 1992, and that the replacement factor for substituting a Class I substance with a VOC 

alternative is one. EPA believes that these assumptions grossly overestimate the amount of VOCs that 

could potentially be released, which is consistent with the objective of conducting a screening-level 

assessment.

8.2VOC EMISSIONS FROM ALL SOURCES

The VOCs from both anthropogenic and biogenic sources are considered for purposes of this analysis 

as emissions of VOCs from all sources (i.e., background). Attachment 8-A provides details on the 

calculation of total (background) VOCs from all sources. Refer to Attachment 8-A for the breakdown 

of total emissions for the nation, for each of the six areas as taken from the Urban Airshed Model 

(UAM), and for a description of the UAM.

 

 

w

See Chapter 4 for description of the Vintaging Model.
8.3COMPARISON OF VOCS FROM SUBSTITUTES TO VOCS FROM ALL SOURCES

The comparison between total nationwide VOC emissions from all sources (21,070,000 MT) and 

VOC emissions from ODS substitutes in the refrigeration and air conditioning industry in 1992 (67,295 

MT) results in a national increase in total VOCs of no more than about 0.32 percent. 

EPA does not expect to see any significant difference between the national ratio and the regional 

ratios, and therefore has not estimated VOC increases in detail for each region in Attachment 8-A (as 

was done for several other sectors). However, releases from refrigerant and air conditioning use in a 

concentrated area were roughly evaluated by placing several of the "worst" possible hypothetical 

factories in that area, assessing emissions, adding this to a per-capita emissions amount (to account for 

releases from units in operation), and comparing the potential VOC emissions to the total VOC 

emissions from all sources in that area.

In the sample region, Trane was chosen as the factory with the highest estimated potential air 

emissions (because of its size). It was assumed that Trane manufactures all industrial process 

equipment in one factory. (Industrial process equipment factories account for some of the highest VOC 

releases of any equipment-producing factories; see the general population analysis for more details.) 

From the analysis on general population risk for the refrigeration and air conditioning sectors, VOC 

releases from three of these facilities were estimated to be 74 MT/yr. Next, the per-capita emissions 

were added in to account for non-factory sources. To do this, the 67,295 MT/yr emissions estimated 

from the vintaging model were used and it was assumed that there are 250 million people in the United 

States. Indianapolisahas a population of 780,000 people, yielding a total annual release of 210 MT/yr 

for non-factory sources. Total VOCs from hydrocarbon substitutes in the refrigerant and air 

conditioning sector in Indianapolis thus is estimated at 284 MT/yr. This increase is 0.43 percent of the 

total VOCs from all sources in Indianapolis (66,640 tons). Using data from Systems Applications 

International (SAI),band the assumption that one month of VOC emissions (23.67 MT) occurs 

instantaneously and enters a 3,000 foot high column of air over Indianapolis (which has an area of 

approximately 10

12 m2

), ozone levels would increase by about 12.8 ppt. When added to Indianapolis' 

current ozone level of 0.121 ppm, the increase would be insignificant, especially compared to the 

amount needed to change Indianapolis' ozone classification to the next worse nonattainment level (i.e., 

moderate at 0.138 ppm ozone). 

8.4CAVEATS AND LIMITATIONS

EPA believes that actual VOC increases due to refrigerants will be less than presented here for 

several reasons, including:

 VOC emissions controls required by EPA and the states will likely be used (Attachment 8-B 

describes the expected impact of VOC controls);

 Improved waste minimization and other housekeeping techniques will likely be used;

 

 

a

Indianapolis was chosen because it was the area from Attachment 8-A with the smallest amount of 

total VOCs, and thus is the most sensitive to percent changes in total VOCs.

 

b This mass-balance model was developed by ICF Incorporated as a simple screening-level tool for 

calculating a "bounding" estimate of VOC increases from ODS substitutes. This model was not 

peer-reviewed by EPA, nor was it developed for purposes of determining a central tendency or even a high 

end estimate of potential increases in VOC concentrations.
13

 VOCs will not have 100 percent of the market share.
14

CHAPTER 8 REFERENCES

Reid, Steven. Systems Applications International (SAI). 1990. May-June. San Rafael, CA. 

Personal communication.
ATTACHMENT 8-A

ESTIMATION OF TOTAL VOC EMISSIONS FROM ALL SOURCES IN 1995

The estimates for total VOC emissions from all sources incorporate both anthropogenic (including 

mobile sources) and biogenic sources. For Los Angeles, Philadelphia, Atlanta, and Dallas, estimates of 

VOC emissions for 1995 were extracted directly from the latest Urban Airshed Modelaresults (June 

1990). For Indianapolis and Hennepin, VOC emissions estimates for 1995 were not available (nor were 

estimates for any other marginal nonattainment or attainment area). Similarly, anthropogenic and 

biogenic estimates were not readily available for nationwide 1995 VOC emissions. Therefore, 

anthropogenic emissions for 1985 were first obtained from the National Acid Precipitation Assessment 

Program (NAPAP) emissions inventory. These 1985 figures then were adjusted for 1995 using 

economic indicator data from the Bureau of Economic Analysis (BEA) Regional Projections Data 

System (June 1990). The biogenic emissions were obtained by averaging seasonal biogenic VOC data 

from the Regional Biogenic Emissions Inventory System (1990)b. These biogenic emissions were 

assumed to remain the same for 1995. The figures obtained from this analysis are presented in Exhibit 

8-A-1.

EXHIBIT 8-A-1

TOTAL VOC EMISSIONS FROM ALL SOURCES IN 1995 (TONS)

Area

Current

Status

Anthropogenic

Emissions

Biogenic

Emissions

Total VOC

Emissions

Los Angeles, 

CA

Extreme

Nonattainment

762,485 295,285 1,057,770

Philadelphia, 

PA

Severe

Nonattainment

760,295 230,315 990,610

Atlanta, GA Serious

Nonattainment

244,550 466,105 710,655

Dallas, TX Moderate

Nonattainment

360,620 253,310 613,930

Indianapolis, IN Marginal

Nonattainment

71,588 1,718 73,306

Hennepin, MN Attainment 82,022 2,078 84,100

United States -- -- -- 23,176,700

 

 

a UAM, managed by Systems Application International (SAI), is a three dimensional photochemical 

grid model designed to calculate concentrations of both inert and chemically reactive pollutants by 

simulating physical and chemical processes that occur in the atmosphere. UAM is EPA's recommended 

model for photochemical pollutant modeling applications involving entire urban areas. For more 

information, see: Systems Applications, Inc., User's Guide for the Urban Airshed Model, developed by 

SAI for Office of Air Quality Planning and Standards, June 1990.

 

b

Systems Applications International. 1990. VOC Analysis Support. Memorandum from Steve 

Reid, SAI, to Shailendra Reddy, ICF. March 19, 1990.

ATTACHMENT 8-B

VOC CONTROLS

Facilities in ozone nonattainment areas switching from ODSs to VOCs may be required to offset the 

VOC emissions from their facility so that net VOC emissions decrease within the nonattainment area. 

Within nonattainment areas, major sources of emissions are subject to the provisions of the New Source 

Review (NSR) program. This program requires affected sources to reduce emissions to the lowest 

achievable emissions rate (LAER), and to offset new VOC emissions increases with reductions obtained 

within the facility or at other facilities located within the nonattainment area.

The NSR program affects "major sources" in nonattainment areas, and the definition of major 

source depends primarily upon the potential of the source to emit pollutants (potential emissions). 

Potential emissions are the amount of pollutant the source is capable of emitting in the absence of any

federally enforceable emission limitation. These amounts are similar to those estimated for individual 

facilities in the SNAP analyses. The potential emissions necessary for a source to be defined as major is 

a function of the classification of the ozone nonattainment area, with the amount of emissions necessary

to be defined as a major source becoming smaller as ozone nonattainment problems of the area become 

greater (Exhibit 8-B-1). 

EXHIBIT 8-B-1

MAJOR SOURCE DEFINITION AND OFFSET REQUIREMENTS

Nonattainment Area 

Classification 

Major Source Definition

(Tons per Year)

Offset Ratios

(VOC reduct.:VOC incr.)

Marginal 100 TPY 1.1 : 1

Moderate 100 TPYa1.15 : 1

Serious 50 TPYa1.2 : 1

Severe 25 TPYa1.3 : 1

Extreme 10 TPYa1.5 : 1

a

States have the option of electing to define major source at 5 tons/yr (and accepting other conditions) as opposed to demonstrating 

further reasonable progress. See text.

It should be noted that some states may elect to opt out of the reasonable further progress (RFP) 

demonstration required by the CAA, which requires states with some classifications of nonattainment 

areas to demonstrate a 15 percent reduction in VOC emissions within the first six years of enactment 

(i.e., by November 1996). States electing to opt out of the RFP demonstration must define major source 

at the 5 ton/yr level and accept other conditions. 

The CAA also requires that major sources in nonattainment areas any offset any new VOC emissions 

with reductions in VOC emissions from within their facility or from other facilities located within the 

nonattainment area. This offset requirement results in a net decrease in VOC emissions for sources 

affected by the NSR program. As shown in Exhibit 8-B-1, the required offsets are a function of the 

classification of the nonattainment area and increase with increasing ozone nonattainment status.

Sources affected by the NSR program are also required to reduce emissions to LAER. LAER 

determinations are typically based on the minimum expected performance of air pollution control 
devices. The reductions achievable by control devices are well established and as shown in Exhibit 

8-B-2 exceed 95 percent.

EXHIBIT 8-B-2

EFFECTIVENESS OF COMMON VOC CONTROL DEVICES

Control Device Minimum Expected Reduction 

Efficiency (Percent)

Thermal Oxidizer 98%

Carbon Absorber 95%

Condenser 95%

Because facilities switching to VOCs would be required to install LAER, and controls are capable of 

reducing emissions by 95 percent, EPA would expect the projected increases in VOC from NSR affected 

facilities to be reduced by at least 95 percent. These facilities must offset any residual emissions (i.e., 

the remaining 5 percent) by the amount specified in Exhibit 8-B-2, thus mitigating any impacts from 

switching from ozone depleting substances to VOCs.