1 May 26, 2009

Significant New Alternatives Policy Program

Refrigeration and Air Conditioning Sector

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

Refrigeration.

Substitute: Propane

This risk screen contains no Clean Air Act (CAA) Confidential Business Information (CBI) and, 

therefore, may be disclosed to the public.

1. INTRODUCTION

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

diplomatic and legislative efforts that have taken place over the past decade, including the Montreal 

Protocol and the Clean Air Act Amendments of 1990 (CAAA). The U.S. Environmental Protection 

Agency (EPA), as authorized by Section 612 of the CAAA, is developing a program to evaluate the 

human health and environmental risks posed by alternatives to ODS. The main purpose of EPA's 

program, called the Significant New Alternatives Policy (SNAP) Program, is to identify acceptable and 

unacceptable substitutes for ODS in specific end uses. 

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

assessment of potential human health and environmental risks posed by the substitute in specific 

applications. EPA has already screened a large number of substitutes in many end uses within all of the 

major ODS-using sectors, including refrigeration and air conditioning, solvent cleaning, foam blowing, 

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

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

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

conditioning sector (EPA 1994) (hereinafter referred to as the Background Document) by adding to the 

list of potential substitutes for specific end-uses of CFC-12, HCFC-22 and R-502 in this sector. The 

proposed end-use application considered in this analysis is retail food refrigeration, specifically ice cream 

cabinets. The specific proposed CFC-12, HCFC-22 and R-502 substitute examined in this report is 

propane (R-290). The substitute would only be used in new equipment, not in retrofitted equipment. 

The proposed substitute, propane, may contain minute quantities of impurities. Table 1 details the 

impurities which may be present in the substitute and notes the maximum estimated concentrations of 

these impurities.

Table 1. Composition of the Substitute.

Substitute Percent by Weight 

Propane 99.5%

Potential Impurities Maximum Concentration (ppm v/v)

Ethane 1700

Propylene 300

n-Butane 1000

Sulphur 1

Water 12
2 May 26, 2009

The potential risks associated with use of substitutes in retail food refrigeration have been examined at 

length in the Background Document. The reader is referred to this reference for a detailed discussion of 

the methodologies used to conduct this risk screen. Presently, EPA’s SNAP Program has not approved 

any hydrocarbons as a substitute in retail food refrigeration end uses. Of particular concern are the 

flammability risks associated with hydrocarbons during manufacturing, use, servicing, and disposal of 

retail food refrigeration appliances. Occupational exposure modeling was performed to ensure that use of 

the proposed substitute in the application listed above did not pose unacceptable risk to workers during 

equipment manufacture. Modeling was performed at the end-use to ensure that potential catastrophic 

releases of the substitute did not pose unacceptable risk to store employees and customers in locations 

where the ice cream cabinets are in use. Lastly, general population exposure modeling was performed to 

ensure that the proposed substitute would not pose unacceptable risk to the population at large. 

Section 2 of this report summarizes the results of the risk screen for the proposed substitute. The 

remainder of the report is organized into the following sections:

 Section 3: Atmospheric Assessment

 Section 4: Flammability Assessment

 Section 5: Asphyxiation Assessment

 Section 6: Toxicity Assessment

 Section 7: Volatile Organic Compound Assessment 

 Section 8: References

2. SUMMARY OF RESULTS

Propane is recommended for SNAP approval for retail ice cream cabinets. EPA's risk screen indicates 

that the use of the proposed substitute will be less harmful to the atmosphere than the continued use of 

CFC-12, HCFC-22 and R-502. No significant toxicity risks to workers, consumers, or the general 

population are expected according to occupational and end-use exposure modeling. Flammability models 

indicate that risks of explosions are not a concern for store employees or customers. To further protect 

against the limited risk of explosion, it is recommended that the cabinets not be used in small, poorly 

ventilated spaces (see Section 4). Caution must be used in manufacturing facilities and by refrigeration 

technicians to minimize explosion risk while in the presence of large quantities of the substitute. This 

includes installation of proper safety equipment during manufacturing, transportation, and storage and 

providing proper training and certification to technicians. EPA recommends that American Society of 

Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standards 15 and 34 be followed.

3. ATMOSPHERIC ASSESSMENT

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

propane in the retail food refrigeration sector. The ODP, GWP, and atmospheric lifetime (ALT) of the 

proposed substitute are presented in Table 2.

The environmental impacts resulting from use of propane are generally in the range of those predicted for 

other substitutes examined in the Background Document. The substitute is substantially less harmful to 

the ozone layer, has less climate impact, and a shorter atmospheric lifetime compared to CFC-12, HCFC22 and R-502.
3 May 26, 2009

Table 2. Atmospheric Impacts of Propane Compared to CFC-12, HCFC-22 and R-502.

Refrigerant Ozone Depleting Potential 

(ODP)

Global Warming Potential 

(GWP)

Atmospheric Lifetime

years (ALT)

Propane 0

a 3

a <1b

CFC-12 1

c 8,100d 100c

HCFC-22 0.055 c 1,500 d 12 c

R-502 e 0.33 5,478 NA

NA = Not Available

a Propane SNAP Submission (Ben and Jerry’s/Unilever 2008).

b Atmospheric lifetime (ALT) not provided in SNAP submission. Wuebbles (2003) indicates that propane has an ALT of 5 – 21 

days.

c Available at: http://www.epa.gov/ozone/ods.html.

d IPCC, Second Assessment Report (1996).

e R-502 is a blend consisting of HCFC-22 (49%) and CFC-115 (51%). The ODP and GWP presented for this blend were

calculated using values from http://www.epa.gov/ozone/ods.html and IPCC’s Second Assessment Report (1996), respectively.

4. FLAMMABILITY ASSESSMENT

Propane is flammable when its concentration in air is in the range of 2.1%-9.5% by volume (this is equal 

to 21,000 ppm to 95,000 ppm). In the presence of an ignition source (e.g., static electricity, a spark 

resulting from a closing door, or a cigarette), an explosion or a fire could occur when the concentration of 

propane is within these flammability limits. The remainder of this section addresses the potential for 

flammability risks at the end-use, and during manufacture and servicing and provides a discussion of 

measures to be taken to ensure safe use.

The proposed use of this substitute is in ice cream cabinets which could reasonably be expected to be 

located either in the main area of a store, or in a storage room. Because a storage room could be much 

smaller than the main area of a store, a reasonable worst-case scenario analysis was performed to model 

catastrophic release of the refrigerant in a storage room. For the analysis, a storage room with a volume 

of 42 m3 was assumed.1 In the analysis, the full charge2of the unit is assumed to be emitted over the 

course of one minute and the model conservatively assumes 2.5 air exchanges occur per hour. Horizontal 

stratification is also assumed since propane is denser than air and will settle in higher concentrations 

closer to the ground. In order to simulate the horizontal concentration gradient that will occur because of 

the weight differential between the refrigerant and air, it is assumed that 95 percent of the leaked 

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

evenly in the remaining volume (Kataoka 1999).

Under catastrophic release scenarios,3the maximum instantaneous concentration of propane in the lower 

stratum of the room would be approximately 66 percent of its lower flammability limit (LFL) for the 

room size assumed, as shown in Table 3. The maximum instantaneous concentration is lower in the 

upper stratum of the room, as only five percent of the leaked refrigerant is present in this stratum, and this 

stratum has a greater volume than the lower stratum. For flammability to be of concern under the 

conservative (protective) assumptions described above, the volume of the storage room would have to be 

28.5 m3 (1,006.5 ft3). Assuming a square room with a ceiling height of 3 m (9.8 ft), this equates to a 3.1 x 

3.1 m (10.1 x 10.1 ft) storage room. As storage rooms can be of varying size, and because boxes and 

 

1 This room was considered a ‘high risk room’ due to its small size and poor ventilation. (Ben and Jerry’s/Unilever 

2008)

2 The charge size used in all models in this analysis is 150g of propane. The submitter notes that the cabinets will 

have a charge size of about 90g; however the maximum charge will be 150g (Ben and Jerry’s/Unilever 2008). To 

ensure all models address a reasonable “worst-case,” the maximum charge size was chosen for use in the models.

3 The submitter notes that “catastrophic leaks during operation have not been recorded.” 
4 May 26, 2009

other equipment in the room may reduce the effective volume of the room, it is therefore recommended 

that propane cabinets not be installed in small, poorly ventilated spaces, to avoid the risk of fire and 

explosion. However, for average sized rooms the risk of explosion is minimal. Cutting a hole in the 

bottom of storage room doors (to act as a vent and increase air circulation) and the installation of leak 

prevention devices would further protect against the limited risk of explosion. For example, in 

commercial refrigeration end-uses, refrigerant leak prevention systems can be used to capture leaked 

refrigerant in a receiving tank during over pressure events, rather than venting the refrigerant to the 

atmosphere.4 Additionally, in motor vehicle air-conditioning, an outflow prevention device can be used 

to prevent leakage events when the heat exchanger of a unit is damaged.5ICF recommends that similar 

safety devices be installed within units containing propane to further reduce the risk of explosion.

Table 3. Flammability Assessment

Room Type/Appliance 

Type

Reasonable Worst-Case Scenario Flammability Threshold Scenario

Room Size (m3) Maximum 

Instantaneous 

Concentration 

(ppm) a,b

Room Size (m3) Maximum 

Instantaneous 

Concentration 

(ppm) a,b

Storage Room/Ice Cream 

Cabinet

42 (1,483 ft3) 13,780 28.5 (1,006.5 ft3) 20,308

a Lower Flammability Limit of propane is equal to 21,000 ppm

b Values provided in these columns refer to the concentration in the lower stratum of the room. 

 

Catastrophic releases of large quantities of refrigerant during servicing and manufacturing, especially in 

areas where large amounts of refrigerant are stored, could cause an explosion. For this reason, it is 

important that only properly trained and certified refrigerant technicians handle propane. The submitter 

has provided information regarding their training program for service technicians. The program includes 

detailed information covering important topics such as potential ignition sources, proper tools to use with 

flammable refrigerants, safe workplace behavior and service procedures. At the end of the training, 

technicians must pass a multiple choice assessment (Ben and Jerry’s/Unilever 2008). All technicians who 

will be servicing cabinets using propane should receive this training and be required to pass the 

assessment. As a further precaution, propane storage and transport equipment should be installed with 

safety devices that minimize the likelihood of catastrophic releases. For example, NFPA 58 Liquefied 

Petroleum Gas Code (NFPA 2008) requires the use of overfill protection devices (OPD) on cylinders to 

minimize the likelihood of leaks. The NPFA 58 Code also contains storage and transportation 

requirements/guidelines. Similar equipment safety and procedural requirements should be implemented

for this substitute. 

It is important that the strictest standards be followed during the manufacture of these ice cream cabinets. 

It is recommended that refrigerants be properly stored and caution used within manufacturing facilities to 

minimize explosion risk and that workers adhere to the requirements set by OSHA under 29 CFR 1910. 

OSHA requirements include proper ventilation and storage practices within manufacturing facilities to 

prevent fire and explosion. Proper ventilation should be maintained at all times during the manufacture of 

equipment containing propane through adherence to good manufacturing practices. If refrigerant levels in 

the air surrounding the equipment rise above one-fourth of the lower flammability limit,

6

the space should 

be evacuated and re-entry should only occur after the space has been properly ventilated. Ventilation is 

also of the utmost importance to mitigate the risk of fire or explosion when servicing equipment using 

propane. During servicing operations, technicians should ensure that proper ventilation is in place 

 

4

http://www.freepatentsonline.com/5259204.html

5

http://www.freepatentsonline.com/6966365.html

6 OSHA regulation 29 CFR 1910.110 considers ventilation adequate “when the concentration of the gas in a gas-air 

mixture does not exceed 25 percent of the lower flammable limit.”
5 May 26, 2009

through the use of fans (or other mechanical ventilation devices) and portable refrigerant detectors should 

be used to alert technicians to the presence of flammable gases in the area. 

5. ASPHYXIATION ASSESSMENT

The risk of asphyxiation for a reasonable “worst-case” scenario was investigated for propane. This 

analysis considers the same small storage room as in Section 4. This analysis does not consider conditions 

that are likely to occur that would reduce the levels to which individuals would be exposed, such as open 

doors or windows, fans operating, conditioned airflow (either heated or cooled), or even seepage between 

the door and door frame. 

The maximum charge of propane necessary to reduce the oxygen levels to 12 percent in air,

7

in a storage 

room of volume 42 m3(1,483 ft3), was calculated, assuming horizontal stratification of the refrigerant and 

the air. Horizontal stratification is assumed since propane is denser than air and will settle in higher 

concentrations closer to the ground. Assuming that nitrogen and oxygen retain the same relative volumes 

in the rooms with the balance composed entirely of propane, and that the pressure of the room does not 

increase significantly with the addition of the refrigerant, a charge of approximately 904 g would be 

necessary to reach 12 percent oxygen in the lower stratum. This amount represents more than six times 

the maximum intended charge of approximately 150 g for a single propane ice cream cabinet. Charge 

requirements to reach the same effect in the upper strata would be even higher because of the stratum’s 

larger volume. For asphyxiation to be of concern with the proposed charge size, under the conservative 

(protective) assumptions described above, the volume of the storage room would have to be about 6.96 m

3

(245.8 ft3). Assuming a square room with a ceiling height of 3 m (9.8 ft), this equates to a 1.5 x 1.5

m (5 x 5 ft) storage room.

The results of the asphyxiation assessment are summarized in Table 4 below. EPA does not believe that 

the use of propane in this end-use poses a significant risk of asphyxiation or impaired coordination to 

store employees or customers. 

Table 4. Asphyxiation Assessment

Room 

Type/Appliance 

Type

Appliance 

Charge (g)

Reasonable Worst-Case Scenario Asphyxiation Threshold Scenario

Room Size (m3) Charge Causing 

Impairment (g)a

Room Size (m3) Charge Causing 

Impairment (g)a

Storage Room/ 

Ice Cream 

Cabinet

150 42 (1,483 ft3) 904 6.96 (245.8 ft3) 150

a Values provided in these columns refer to the charge required to cause impairment in the lower stratum of the room.

6. TOXICITY ASSESSMENT

6.1 TOXICITY REFERENCE VALUES

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

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

different scenarios. For the occupational exposure analysis, potential risks from chronic and acute worker 

exposure were evaluated by comparing exposure concentrations to available occupational exposure limits. 

Occupational exposure limits are typically established for either an eight-hour or ten-hour time period for 

long-term exposure, such as the Workplace Guidance Levels (WGLs), or for a 10 to 30-minute period for 

short-term exposure, such as the Emergency Guidance Levels (EGLs), as shown in Table 5. Because they 

are designed to assess risks from acute exposure, emergency guidance levels are used to assess risks from 

 

7 Twelve percent oxygen in air is the NOAEL for hypoxia (ICF 1997). 
6 May 26, 2009

short-term consumer exposures. Reference concentrations (RfCs) are used to assess risks to the general 

population from exposure to ambient air releases and to assess potential risks associated with chronic 

consumer exposures. A list of the relevant toxicity limits is shown in Table 5. Table 6 provides 

definitions for acronyms used in Table 5. EPA’s approach for identifying or developing these values is 

discussed in Chapter 3 of the Background Document. 

Table 5. Toxicity Levels of Propane and Potential Impurities

Long-term Exposure

ppm

Short-term Exposure

ppm

Reference Concentration (RfC)

mg/m3

Substitute

Propane 1000 a

(OSHA PEL/NIOSH REL)

2100 a(IDLH) 0.9 b

Potential Impurities

Ethane NA c NA c NA

Propylene NA d NA d NA

n-Butane 800 e(NIOSH REL) NA 0.95 b

Sulphur NA NA NA

NA = Not Available

a "Based on acute inhalation toxicity data in humans (ACGIH 1991; Braker 1980), a value much greater than 10,000 ppm 

would have been appropriate. However, the revised IDLH for propane is 2,100 ppm based strictly on safety considerations 

(i.e., being 10% of the lower explosive limit of 2.1%)." (NIOSH 1996)

b SNAP Refrigerant Background Document (EPA 1994).

c Ethane is a "simple asphyxiant." http://www.osha.gov/dts/chemicalsampling/data/CH_238900.html

d Propylene is a "simple asphyxiant." http://www.osha.gov/dts/chemicalsampling/data/CH_264442.html

e http://www.cdc.gov/niosh/npg/npgd0068.html

Table 6. Explanation of Toxicity-Related Acronymsa

Organization Definition

OSHA Occupational Safety and Health Administration

NIOSH National Institute for Occupational Safety and Health

Exposure Limit Definition Explanation

IDLH Immediately Dangerous to Life and 

Health

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

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

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

REL Recommended Exposure Limit This is a 10-hour time-weighted average exposure limit set by NIOSH.

RfC Reference Concentration A concentration “designed to protect the general population against 

adverse systemic (i.e., noncancer) effects.”

aAll information in this table taken from EPA (1994).

6.2 OCCUPATIONAL EXPOSURE 

Occupational exposure modeling was performed for the proposed substitute to ensure that use of the 

substitute does not pose an unacceptable risk to workers. The methodology used for this screening 

assessment is based on the one used in the occupational exposure and hazard analysis described in 

Chapter 5 of the Background Document. A box-model approach was used to evaluate potential worker 

exposure to alternative refrigerants. This approach 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). This model takes into consideration the 

duration and magnitude of the resulting exposure which is influenced by 1) duration and intensity of the 
7 May 26, 2009

release, 2) rate at which contaminated air is diluted with uncontaminated air, 3) proximity of the worker 

to the source of the release, and 4) the length of time the worker remains in the affected space. 

Estimates of refrigerant release per event for various release scenarios and data on number of events were 

obtained from the Vintaging Model.8 The release per event was conservatively assumed to be 1 percent 

of the equipment charge during manufacturing and 3 percent of the equipment charge during disposal.9 

The release rate per event 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 

containing the substitute produced per plant per year divided by 365 workdays per year. For the purposes 

of this model, it is assumed that propane will have a market penetration rate of 23%

10 and that one

production facility will be in operation. These assumptions result in approximately 274

events/manufacturing facility/workday. For disposal, it was conservatively assumed that 100 units are 

disposed during an 8-hour work day nationwide. 

The maximum time weighted average (TWA) exposure was estimated for each exposure scenario, and 

this value compared to the Workplace Guidance Levels (WGLs) for propane and the potential impurities 

in the substitute. The modeling results indicate that the short-term (15-minute and 30-minute) and longterm (8-hour) worker exposure concentrations are at a maximum, about 50 percent of the WGLs. Table 7 

displays the maximum estimated 15-minute TWA occupational exposure levels of propane and the 

potential impurities in the substitute. Even these maximum estimated short-term occupational levels are 

significantly lower than the 8-hour or 10-hour long-term WGLs, and therefore occupational exposure to 

propane and the potential impurities is not considered a toxicity threat.

Table 7. Occupational Risk Assessment

Maximum 15-

minute TWA 

Occupational 

Exposure Levels 

(ppm)

Workplace 

Guidance Levels 

(ppm) a

Workplace 

Guidance Levels 

Time Period

Substitute

Propane 502 1000 10-hour TWAb

Potential Impurities

Ethane 0.9 NA NA

Propylene 0.2 NA NA

n-Butane 0.5 800 10-hour TWA

Sulphur 5.4 x 10-4 NA NA

NA = Not Available

a. See Table 5 for more information.

b. The WGL for Propane is set as a 1000 ppm 8-hr TWA by OSHA and a 10-hr TWA by NIOSH. 

6.3 END-USE EXPOSURE

This section presents estimates of potential store employee and customer exposures to propane in ice 

cream cabinets. An exposure analysis was performed to examine potential catastrophic release of the 

 

8

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

the use and emissions of various fluorocarbons and their substitutes over a period of several years across more than 40 different 

applications. The model tracks the use and emissions of various compounds for the annual vintages of new equipment that enter 

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

in operation, and the initial ODS substance that the equipment contained. 

9 During disposal it is assumed that only 90 percent of the refrigerant charge remains in the unit. 

10 This number conservatively assumes that all Unilever cabinets in North America (a figure provided in the SNAP Submission) 

are in the US and that all will be replaced with R290 cabinets by 2010. This number of cabinets was divided by the number of

predicted new small retail refrigeration units produced in 2010, from the Vintaging Model.
8 May 26, 2009

substitute in a small storage room (as in Sections 4 and 5) under a reasonable “worst-case” scenario. The 

analysis was undertaken to determine the 15- and 30-minute TWA exposures for the substitute, which 

were then compared to the standard toxicity limits presented in Table 5 to assess the risk to consumers. 

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

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

which individuals would be exposed.

The model involves a refrigerant leak from an ice cream cabinet into an enclosed storage room of volume

42 m3(1,483 ft3). The model assumes that the individual is present at the start of the leak and the 

individual remains in the room while the refrigerant is released. It is also assumed that horizontal 

stratification causes most of the refrigerant to settle in higher concentrations closer to the ground. In 

order to simulate the horizontal concentration gradient that will occur because of the weight differential 

between the refrigerant and air, it is assumed that 95 percent of the leaked refrigerant mixes evenly into 

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

(Kataoka 1999). Exposure concentrations were calculated using the box model described in the 

Background Document, which was adapted to estimate concentrations on a minute-by-minute basis. In 

the analysis, the full charge of the unit is assumed to be emitted over the course of one minute and the 

model conservatively assumes 2.5 air exchanges occur per hour. 

The highest expected levels of exposure at the end-use based on this analysis occur in the lower stratum 

of the room. The results of the assessment are presented in Table 8.

Table 8. End-Use Exposure Assessment

15-minute TWA 

Exposure (ppm)

30-minute TWA 

Exposure (ppm)

Substitute

Propane 10,414 7,963

Potential Impurities

Ethane 19 15

Propylene 3.4 2.6

n-Butane 11 8.6

Sulphur 0.01 0.009

TWA = Time Weighted Average

While the IDLH for propane is 2,100 ppm, NIOSH (1996) notes that "based on acute inhalation toxicity 

data in humans (ACGIH 1991; Braker 1980), a value much greater than 10,000 ppm would have been 

appropriate. However, the revised IDLH for propane is 2,100 ppm based strictly on safety considerations 

(i.e., being 10% of the lower explosive limit of 2.1%)." Therefore, it is believed that even under the very 

conservative assumptions used in this model, exposures to propane should not pose a toxicity threat. 

Steps to protect against fire or explosion in the space should be taken, as detailed in Section 4. Exposure 

to the minute quantities of the impurities detailed in Table 8 is also not expected to pose a toxicity threat, 

given the low toxicity of these substances. Should catastrophic release from a cabinet located in the main

area of a store occur, exposure levels are not expected to pose a toxicity threat as the room volumes in the 

store would be larger than those used in this model.

11

 Thus, exposure concentrations would be even lower 

in the main area of the store.

 

11 An Armines (2008) study presents data from site visits to California convenience stores, “minimarkets” and 

supermarkets during which the minimum store area encountered was 100 m2. Assuming a 3 m ceiling height (as in 

the scenarios used in this risk screen), this is equal to a volume of 300 m

3

, or more than seven times the volume of 

the store room used in this analysis.
9 May 26, 2009

6.4 GENERAL POPULATION EXPOSURE

In the SNAP Background document for refrigerants (EPA 1994), the RfC value for propane is 0.9 m/m3.

We compared this RfC to estimated factory releases and on-site releases. This gives a ratio of exposure 

concentration to RfC that varies between 1.9 x 10-4to 3.5 x 10-1, depending on the type of release 

scenario.12 Ratios of exposure concentration to RfC for the substitute’s impurities (for which RfCs are 

available) were even lower. Since the exposure concentrations for the substances are lower than the RfC 

values, the substitute is not expected to pose a toxicity threat to the general population.

7. VOLATILE ORGANIC COMPOUND (VOC) ASSESSMENT

Propane has not been exempted as a VOC under the CAA (40 CFR 51.000). However, through 

regulations and standard industry practices, VOC emissions should be controlled. Chapter 8 of the 

Background Document shows that potential emissions of VOCs from all substitutes for all end uses in the 

refrigeration and air conditioning sector are likely to be insignificant relative to VOCs from all other 

sources (i.e., other industries, mobile sources, and biogenic sources). Additional analysis shows that even 

if all ice cream cabinets produced by Unilever/Ben and Jerry’s in one year13 were to leak their entire 

charge over the course of the year (extremely unlikely), the resulting annual VOC emissions would be 

only about 8.5x10-5percent of all annual anthropogenic VOC emissions.14 As these emissions of propane 

are several orders of magnitude less than other anthropogenic emissions, the environmental impacts of 

these VOCs are not considered a threat.

8. REFERENCES

ACGIH. 1991. Propane. In: Documentation of the threshold limit values and biological exposure indices. 

6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 1286-

1287. 

Armines. 2008. Inventory of Direct and Indirect GHG Emissions from Stationary Air Conditioning and 

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

Conditioning. Provisional Final Report. June 2008. Available at: <

http://www.arb.ca.gov/cc/commref/armines_report_03_625.pdf>.

Ben and Jerry’s/Unilever SNAP Submission. 2008. Significant New Alternatives Policy Program 

Submission to the United States Environmental Protection Agency, October 2008. 

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

pp. 615623. 

EPA 2008. Volatile Organic Compounds – National Summary of VOC Emissions. Last updated 21 

October 2008. Accessed 4 March 2009. Available at 

<http://www.epa.gov/air/emissions/voc.htm>.

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

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

Stratospheric Protection Division. March, 1994.

 

12 Release scenarios include factory and on-site releases, with and without recycling of the refrigerant.

13 Conservatively assuming that all Unilever cabinets in North America (a figure provided in the SNAP Submission) 

are in the US and that all will be replaced with R290 cabinets.

14 This figure was calculated using 2002 annual VOC emissions data from EPA (2008).
10 May 26, 2009

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

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

New London, CT.

Kataoka. 1999. “Allowable Charge Limit of Flammable Refrigerants and Ventilation Requirements.” 

Draft Proposal. O. Kataoka/Daikin/Japan, June, 1999.

NFPA. 2008. NFPA 58: Liquefied Petroleum Gas Code. National Fire Protection Agency.

NIOSH. 1996. Propane: IDLH Documentation. August 1996. Accessed 17 Feburary 2009. Available 

online at: < http://www.cdc.gov/niosh/idlh/74986.html>.

Sheldon, L.S., et al. 1989. "An Investigation of Infiltration and Indoor Air Quality." New York State 

Energy Research & Development Authority, Report 90-11.

Wuebbles 2003. Personal communication with Don Wuebbles. E-mail. July 21, 2003.