Document ID: EPA-HQ-OAR-2009-0286-0010
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-05-10T04:00Z

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.

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   SEQ Table \* ARABIC  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

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

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.

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, HCFC-22 and R-502.

Table   SEQ Table \* ARABIC  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	0a	(3a	<1b

CFC-12	1c	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.

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.  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.  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, the 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 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.  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.    ICF
recommends that similar safety devices be installed within units
containing propane to further reduce the risk of explosion.

Table   SEQ Table \* ARABIC  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, 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 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.  

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, 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 m3 (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   SEQ Table \* ARABIC  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.

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
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   SEQ Table \* ARABIC  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   SEQ Table \* ARABIC  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 escape-impairing 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 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.  
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.  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% 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 long-term (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 substitute in
a small storage room (as in Sections   REF _Ref222646985 \r \h  \*
MERGEFORMAT  4  and   REF _Ref222646989 \r \h  \* MERGEFORMAT  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   REF _Ref222646985 \r \h 
\* MERGEFORMAT  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.  Thus, exposure
concentrations would be even lower in the main area of the store.

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 10-4 to 3.5 x 10-1,
depending on the type of release scenario.  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.

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 year were to leak their entire charge over the course
of the year (extremely unlikely), the resulting annual VOC emissions
would be only about 8.5x10-5 percent of all annual anthropogenic VOC
emissions.  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. 12861287. 

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.

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.

 This room was considered a ‘high risk room’ due to its small size
and poor ventilation. (Ben and Jerry’s/Unilever 2008)

 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.

 The submitter notes that “catastrophic leaks during operation have
not been recorded.”  

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

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

 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.”

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

 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.    

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

 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. 

   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 m3, or more than seven times the volume of the store
room used in this analysis.

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

 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.

 This figure was calculated using 2002 annual VOC emissions data from
EPA (2008).

	 				   May 26, 2009