Transitioning to Low-GWP Alternatives in Residential and Commercial Air Conditioningand Chillers


TRANSITIONING TO LOW-GWP ALTERNATIVES
in Residential and Commercial Air Conditioning
and Chillers
Background
This fact sheet provides current information on low global
warming potential (GWP)1 alternative refrigerants to high-GWP
hydrofluorocarbons (HFCs)for use in residential and commercial
air conditioning (AC) equipment, including chillers. Ill Cs are
powerful greenhouse gases (GHGs) with GWPs hundreds to
thousands of times more potent per pound than carbon dioxide
(C02); however, more low GWP alternatives are becoming
available.
Globally, approximately 80% of HFCs are emitted in the
refrigeration, AC, and motor vehicle AC (MVAC) sectors, with
the remainder accounted for by the foam-blowing, aerosols,
fire suppression, and solvents sectors. While developed
nations have historically accounted for the majority of global
HFC emissions, total HFC emissions in developing nations are
projected to quadruple by 2030. This rapidly increasing rate of
HFC emissions is largely driven by the increased demand for
refrigeration and AC, particularly in the tropical climates of
much of the developing world, and the transition away from
ozone depleting substances (ODS).
HFC refrigerant emissions from AC applications are released
to the atmosphere throughout the lifecycle of equipment—i.e.
during equipment manufacture, installation, operation,
maintenance, and at end ol lile.
Figure 1. Global HFC Emissions in 2020 by Sector
MVAC
/ 13%
Aerosols,
Solvents,
Foams,
and Fire Ext
21%
Other Ref
12%
Commercial
Ref
26%
Global HFC Emissions: 1,084 MMT C02 Eq.
Global HFC Emissions in AC: 306 MMT C02 Eq.
Source: Estimates based on U.S. EPA (2013).
AC Equipment
Residential and commercial AC equipment used iri households
and commercial buildings contain one or more factory-made
assemblies that normally include an evaporator or cooling coil(s),
compressor(s), and condenser(s). These include small AC systems
(self-contained AC and split AC), large AC systems (single
split and multi-split, variable refrigerant flow, and ducted and
packaged rooftop units), as well as chillers. Descriptions of each
of these AC equipment categories are provided below, followed
by Table II, which lists the typical capacity, refrigerant charge, and
annual operational leak rate for each equipment type.

i
1 GWP is a measure of a substance's climate warming impact compared to COn.

-------
Small AC Systems
Source: U.S. EPA (2015d)
Small Self-Contained AC
•	Small hermetically sealed AC units
are used for cooling small rooms
in residential and commercial
buildings
•	The compressor, evaporator, and
condenser are all housed within
a single unit
•	Includes portable units, window-mounted units, through-the-
wall units, and packaged terminal air conditioning
(PTAC) units
•	Portable units utilize flexible ductwork to supply outside air
to the condenser and return heated air to outside of
the room
•	PTAC units are often used in the hospitality industry
(e.g., inside hotel rooms)
•	Packaged terminal heat pumps (PTITI's) are similar to
PI AOs and also provide treating
Small Split AC
•	Small split AC units are used
for cooling single rooms in
residential and commercial
buildings
•	Systems contain two factory-
built units interconnected by a
Source: UNEP (2015c)
refrigerant line; the indoor unit includes the evaporator,
installed inside conditioned room ori the wall, ceiling,
or floor; the outdoor unit includes a compressor and a
condenser
Some systems can operate in reverse and provide heating
in cold weather
Large AC Systems
Large Single Split and Multi-Split AC
•	Larger versions of the
small split system
described above
•	Multi-split systems have
several indoor units connected
to a single outdoor unit
•	Some models are designed to
provide both heating and cooling
Variable Refrigerant Flow
(VRF) Systems
•	More complex multi-split
systems
•	One or more air source
outdoor compressor units
serving multiple indoor fan
coil refrigerant evaporator units

Source: UNEP (2015d)
Source: Pacific Northwest National
Laboratory (2012)
•	Heated or cooled refrigerant moves throughout building
in small diameter pipes and passes through coils in each
conditioned room
•	Systems can deliver heating and/or cooling to different
rooms of the same building simultaneously through
various units
Ducted and Packaged Rooftop Systems
•	In ducted systems, the
evaporator is located in an air
handling unit to cool air
•	In packaged rooftop systems,
the compressor, evaporator,
and condenser are all housed
within a single unit
•	Air is circulated throughout the
building via a ducted air ventilation system
Source: U.S. EPA (2015d)

-------
Chillers
Comfort Cooling
•	Large buildings are often cooled
by a central chiller that pumps
chilled water to heat exchangers
in air handling or fan-coil units
that deliver conditioned air
•	Often located in a machinery
room (large buildings) or
outdoors (small buildings)
•	Small and medium-sized chillers typically use a vapor
compression cycle with positive displacement compressors
(i.e., reciprocating, rotary, scroll, or screw), while large
chillers typically use screw or centrifugal compressors
Source: UNEP (2015e)
Source: AEC Online (2007)
District Cooling
•	Uses a centralized cooling
plant to deliver chilled water
via underground insulated
pipes to several buildings
using a single system
•	Provides AC to multiple buildings
in a central location (e.g., hospitals, universities,
shopping malls, airports)
•	Chillers using vapor compression technology and centrifugal
compressors often used in cooling plant
•	Increasing in popularity; commonly used in the Middle East;
some installations in China, the United States, Northern
Europe, and coastal sites such as Hawaii, Malaysia, and
Mauritius, with sufficient deep water resources
Table 1. Typical AC Equipment Characteristics
Equipment Type
Capacity
(kW)
Refrigerant Charge (kg)
Annual Operational
Leak Rate" (%)
Small Sell Contained AC
2-7
0.2-2
<1
Small Split AC
2-12
0.5-3
1-4
Single Split and Multi-Split (Large)
10-40
3-10
1-4
VRF Systems (Large)
12-150
5-100
1-5
Ducted Systems (Large)
12-750
5-200
2-6
Small/Medium Chillersb
50-750
40-500
2-4
Large Chillers0
750-21,000
500-36,000
2-4
Sources: UNEP (2015a - e) and Johnson Controls (2014).
8 Typical annual operational leak rate does not include additional refrigerant ieaks that can occur during equipment installation, maintenance, servicing, and disposal
B Typically use positive displacement compressors (i.e., reciprocating, rotary, scroll, or screw).
• Typically use screw or centrifugal compressors.
HFC Alternatives and Market Trends
Many residential and commercial AC systems in use contain
ozone-depleting refrigerants CFC-11, CFC-12, and HCFC-22,
which are being phased out globally under the Montreal
Protocol. Many new units sold today contain HFCs, or HFC
blends, namely R-410A and R-407C, with GWP values of
2,088 and 1,774, respectively. A number of lower GWP
alternative refrigerants are available and currently in use or
under development for use in residential and commercial AC
systems—including hydrocarbons, carbon dioxide, ammonia,
water, as well as HFC and III O blends. These alternatives and
their potential applications are described on the next page and
summarized in Table 2.
* HFOs (hydrofluoroolefins) are unsaturated HFCs (i.e., containing a carbon-carbon double bond).

-------
TRANSITIONING TO LOW-GWP ALTERNATIVES in Residential and Commercial Air Conditioning and Chillers
R-290 (Propane) and Hydrocarbon Blends (e.g., R-441A)
•	Successfully used in some regions including China and
India in small AC units that utilize less than 1 kilogram of
refrigerant
•	Used in small self-contained AC and small split AC in Europe,
Far East, Japan, and India
•	Used in small capacities and outdoor applications in
air-cooled chillers in Indonesia, Malaysia, the Philippines,
Europe, and New Zealand
•	R-290 and R-441A are listed acceptable substitutes
(subject to use conditions) in room AC units by the U.S. EPA
Significant New Alternatives Policy (SNAP) program
•	Efficiency and performance expected to be equal to or better
than R-410A, particularly in regions with warmer climates
•	Safety concerns for flammable refrigerants require
technician training and can increase installation costs
Carbon Dioxide (C02, R-744)
•	Can be used in large AC equipment, typically in ducted
systems
•	Air-cooled chillers using R-744 have been introduced in
northern Europe
Ammonia (R-717)
•	Suitable in chillers for numerous building AC applications
and district cooling
•	Used in medium and large chillers with screw or
reciprocating compressors
•	Central comfort cooling chiller plant installations exist in the
Middle East, China, Europe, and the United States
•	Ammonia is listed as an acceptable substitute by the U.S.
EPA SNAP program in vapor compression chillers (with a
secondary loop)
•	Ammonia is also used in absorption systems, which are
listed as acceptable by the U.S. EPA SNAP program for
chillers and in residential and light commercial AC equipment
•	Safety concerns in comfort cooling applications can increase
installation costs and require technician training; restrictions
often apply in some countries due to certain building codes
or regulations
Water (R-718)
•	Developmental chillers demonstrated in the Middle East,
South Africa, and Europe
•	Requires large space and use of complex
compressor technology
HFC-32
•	Small self-contained and split AC systems produced with
HFC-32 are commercially available in 30 countries, including
Japan, India, Indonesia, Australia, and soon in China and the
United States
•	HFC-32 is listed as an acceptable substitute (subject to use
conditions) in room AC units by the U.S. EPA SNAP program
•	Efficiency and performance expected to be equal to or better
than R-410A
Low-GWP Fluorinated Compounds
•	HFO-1234yf and HFO-1234ze(E) have similar properties to
HFC-134a and are under development for ducted and rooftop
unit systems
•	Use of HFO-1234ze(E) is currently under development in
large centrifugal chillers and large AC equipment and
commercially available in small and medium-sized positive
displacement chillers
•	Chillers using HFO-1234ze(E) are available in the
European market
•	HFO-1234ze(E) is listed as an acceptable substitute in
centrifugal, reciprocating, and screw chillers by the U.S. EPA
SNAP program
•	Solstice™ 1233zd(E) is currently used in centrifugal chillers
in Europe, the Middle East, and Japan
•	Solstice™ 1233zd(E) is listed as an acceptable substitute in
centrifugal chillers by the U.S. EPA SNAP program
•	HFO-1336mzz(Z) is under development for use in low
pressure centrifugal chillers
•	HFO-1336mzz(Z) is listed as an acceptable substitute in
centrifugal and positive displacement chillers by the U.S.
EPA SNAP program
HFC/HFO Blends
•	Various blends of HFCs and HFOs (i.e., unsaturated HFCs) are
being developed for all types of AC equipment
•	R-450A and R-513A are listed as acceptable substitutes in
centrifugal, reciprocating, and screw chillers by the U.S. EPA
SNAP program
•	Testing and trials using blends of R-444B, R-446A, and
R-447A, in both small and large AC systems, are ongoing,
with manufacturers in Japan, Korea, China, and New
Zealand developing prototypes
•	Safety regulations may be required for lower flammability
blends (e.g., R-444B, R-446A and R-447A), especially in
larger AC equipment

-------
TRANSITIONING TO LOW-GWP ALTERNATIVES in Residential and Commercial Air Conditioning and Chillers
Table 2. Lower-GWP Alternatives for Residential and Commercial ACa
Refrigerant
GWP"
Small
Self-Contained
ACC
Small Split
ACC
Single &
Multi- Split AC
(Large)0
VRF (Large)0
Ducted
Systems
(Large)0
Chillers0
HFC-32
675
~+
~
~
~
~
~
R-513A
630





~+
R-450A
601





~+
HFO-1336mzz(Z)
9





~+
HFO-1234ze(E)
6




~
~+
R-441A
<5
~+





Solstice™ 1233zd(E)
4.7-7





~+d
HFO-1234yf
4




~

R-290
3
~+
~



~
R-744 (C02)
1




~
~
R-717 (ammonia)
0





~+
Note: R-444B, R-446A, R-447A, and R-718 are currently under development for use in various residential and commercial AC applications.
3 ~ = Available now; ~ = Under Development; + = U.S. EPA SNAP-approved
b GWP values are from IPCC Fourth Assessment Report (2007) and U.S. EPA (2015c).
i: UNEP (2015a-e).
d U.S. EPA SNAP-approved for centrifugal chillers only.
Reducing Emissions from Servicing and Disposal
Refrigerant emissions from AC equipment occur during various
events, including manufacture, operation (i.e., leaks from
fittings, joints, shaft seals, etc.), servicing (i.e., due to loss
of refrigerant from fugitive emissions), and end-of-life (i.e.,
equipment disposal). When leaks are fixed during servicing,
refrigerant recovery is necessary for certain applications.
During servicing events and end-of-life, the refrigerant
losses depend on various factors including the existence of
or compliance with refrigerant recovery laws, the technical
efficiency of refrigerant recovery equipment, and the technical
performance of technicians. Improvements in the technologies
and practices associated with the use of these gases by
manufacturers and technicians, the introduction of alternative
gases and technologies, implementation of refrigerant recovery
laws and standards, and market/policy drivers that provide
financial incentives for recovery may help to offset most HFC
refrigerant emissions from residential and commercial
AC equipment.
Case Study: Hydrocarbon Refrigerants in China
With support from the United Nations Industrial Development Organization (UNIDO) and approval for funding by the Executive Committee
of the Multilateral Fund for the Implementation of the Montreal Protocol in July 2010, two manufacturers in China—Guangdong Meizhi
Co. Ltd and Guangdong Midea Refrigeration Equipment Co. Ltd—conducted a demonstration project to convert R-22 compressors and
split AC units to R-290. The Meizhi production line, which has an annual production capacity of 1.83 million rotary compressors for split AC
systems, was converted to produce R-290 compressors. The Midea production line was converted to an advanced mechanized line producing
200,000 R-290 split units annually. After 30 months of factory conversion the project was completed by the end of 2013 and two types
of compressors (fixed and variable speed) and two types of AC units (split and portable) became available for mass production by these
manufacturers. The R-290 AC units also meet both national and international performance standard requirements.
In converting the plants, engineering controls and safety measures were implemented into the production lines to address the flammability
of R-290, including modified products, tools, parts, equipment, installation procedures, leak detection and containment, staff training, and
technology dissemination. The success of this project and advancement of hydrocarbon-based AC technologies has already influenced other
Chinese manufacturers to invest in conversion activities. For example, in 2015, nine AC manufacturers in China were designated by the
Chinese Ministry of Environmental Protection to receive subsidies to convert to R-290. These advancements are expected to encourage other
manufacturers in other developing countries to invest in alternative AC technologies.

-------
TRANSITIONING TO LOW-GWP ALTERNATIVES in Residential and Commercial Air Conditioning and Chillers
Future Outlook
Together, the suite of known alternative chemicals, new
technologies, as well as better process and handling practices,
can significantly reduce HFC use in both the near and long term.
Many countries are transitioning to lower-GWP alternatives
in AC applications while satisfying the various international
energy efficiency, safety, and environmental standards. The
equipment manufacturers and chemical producers for the AC
References
AEC Online. 2007. "Empower and Logstor to build the UAE's largest pre-
insulated pipe manufacturing facility." Available online at: http://www.
aeconline.ae/13/pdcnewsitem/00/98/45/index 13.html
European Parliament and the Council of the European Union (EU). 2014.
"Regulation (EU) No 517/2014 on fluorinated greenhouse gases and repealing
Regulation (EC) No 842/2006." Official Journal of the European Union. 16
April 2014. Available online at: http://eur-lex.euroDa.eu/leaal-content/EN/
TXT/PDF/?uri=CELEX:32014R0517&from=EN
Intergovernmental Panel on Climate Change (IPCC). 2006. "2006 IPCC
Guidelines for National Greenhouse Gas Inventories." The National
Greenhouse Gas Inventories Programme, The Intergovernmental Panel
on Climate Change, H.S. Eggleston, L. Buendia, K. Miwa, T. Ngara, and K.
Tanabe (eds.). Hayama, Kanagawa, Japan.
Intergovernmental Panel on Climate Change (IPCC). 2007. "Climate Change
2007: The Physical Science Basis." Contribution of Working Group I to
the Fourth Assessment Report of the Intergovernmental Panel on Climate
Change. Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt,
M. Tignor, and H.L. Miller (Eds.). Cambridge University Press, Cambridge,
United Kingdom and New York, NY, USA. September 2007. Available online
at: http://www.iDcc.ch/publications and data/ar4/wa1/en/contents.html
Johnson Controls. 2015. "Model YD Dual Centrifugal Compressor Chillers."
Available online at: http://cgproducts.iohnsoncontrols.eom/YorkDoc/160.69-
EG3.pdf
McNeil, M.A. and V.E. Letschert. 2007. "Future air conditioning energy
consumption in developing countries and what can be done about it: the
potential of efficiency in the residential sector." ECEEE 2007 Summer Study.
Available online at: http://www.eceee.org/librarv/conference proceedings/
eceee Summer Studies/2007/Panel 6/6.306/paper
Pacific Northwest National Laboratory. 2012. "Variable Refrigerant Flow
Systems." Prepared for the General Services Administration by Pacific
Northwest National Laboratory. December 2012. Available online at: http://
www.gsa.gov/portal/mediald/169771/fileName/GPG VRF Report -
FINAL DRAFT 4-16-13
Shecco. 2016. Manufacturers see openings for natural refrigerants in China.
Hydrocarbons 21 Industry News. 14 April 2016. Available online at: http://
www.hvdrocarbons21.com/news/view/6948.
Schwarz, W., B. Gschrey, A. Leisewitz, A. Herold, S. Gores, I. Papst, J.
Usinger, D. Oppelt, I. Croiset, PH. Pedersen, D. Colbourne, M. Kauffeld, K.
Kaar, and A. Lindborg. 2011. "Preparatory study for a review of Regulation
(EC) No 842/2006 on certain fluorinated greenhouse gases." Prepared for the
European Commission. September 2011.
industry are continuing to work on developing new alternatives
that can be marketed worldwide. Although much work remains
to fully develop and adopt some of these low-GWP
alternatives, and some unknowns still remain, the affected
industries have proven through the ODS phaseout that they
can move quickly to develop low-GWP alternatives that protect
the environment.
Technology and Economic Assessment Panel (TEAP). 2013. "Decision
XXIV/7 Task Force Report: Additional Information to Alternatives on ODS."
September 2013. Available online at: http://ozone.unep.org/Assessment
Panels/TEAP/Reports/TEAP Reports/TEAP TaskForce%20XXIV-7-
September2013.pdf
Technology and Economic Assessment Panel (TEAP). 2014. "Decision
XXV/5 Task Force Report: Additional Information to Alternatives on ODS
(Final Report)." October 2014. Available online at: http://ozone.unep.org/
en/Assessment Panels/TEAP/Reports/TEAP Reports/TEAP Task%20
Force%20XXV5-0ctober2014.pdf
Technology and Economic Assessment Panel (TEAP). 2015. "Decision XXVI/9
Task Force Report: Additional Information to Alternatives to ODS." June
2015. Available online at: http://conf.montreal-protocol.org/meeting/oewg/
oewg-36/presession/Background%20Documents%20are%20available%20
in%20English%20onlv/TEAP Task-Force-XXVI-9 Report-June-2015.pdf
United Nations Environment Programme (UNEP). 2011. "2010 Report of
the Refrigeration, Air Conditioning and Heat Pumps Technical Options
Committee." February 2011. Available online at: http://ozone.unep.org/
Assessment Panels/TEAP/Reports/RT0C/RT0C-Assessment-report-2010.
Edf
United Nations Environment Programme (UNEP). 2014. Addendum: Status
Reports and Compliance. Executive Committee of the Multilateral Fund for
the Implementation of the Montreal Protocol, Seventy-third Meeting Paris,
9-13 November 2014. UNEP/0zL.Pro/ExCom/73/17/Add.1. Available online at:
http://www.multilateralfund.Org/73/English/1/7317a1.pdf.
United Nations Environment Programme (UNEP). 2015a. "2014 Report
of the Refrigeration, Air Conditioning and Heat Pumps Technical Options
Committee." February 2015. Available online at: http://conf.montreal-
protocol.org/meeting/mop/mop-27/presession/Background%20
Documents%20are%20available%20in%20English%20onlv/RT0C-
Assessment-Report-2014.pdf
United Nations Environment Programme (UNEP). 2015b. "Fact Sheet 7:
Small Self-Contained Air-Conditioning." UNEP Ozone Secretariat Workshop
on HFC management: technical issues. Bangkok, 20 and 21 April 2015.
Available online at: http://conf.montreal-protocol.org/meeting/workshops/
hfc management-02/presession/English/FS%207%20Small%20self%20
conta ined%20ai r-conditionin g%20final.pdf
United Nations Environment Programme (UNEP). 2015c. "Fact Sheet 8:
Small Split Air-Conditioning." UNEP Ozone Secretariat Workshop on HFC
management: technical issues. Bangkok, 20 and 21 April 2015. Available
online at: http://ozone.unep.org/sites/ozone/files/Meeting Documents/
HFCs/FS 8 Small split air-conditioning Oct 2015.pdf

-------
TRANSITIONING TO LOW-GWP ALTERNATIVES in Residential and Commercial Air Conditioning and Chillers
United Nations Environment Programme (UNEP). 2015d. "Fact Sheet 9: Large
Air-Conditioning (air-to-air)." UNEP Ozone Secretariat Workshop on HFC
management: technical issues. Bangkok, 20 and 21 April 2015. Available
online at: http://ozone.unep.org/sites/ozone/files/Meetina Documents/HFCs/
FS 9 Large air to air air-conditioning Oct 2015.pdf
United Nations Environment Programme (UNEP). 2015e. "Fact Sheet 10:
Water chillers for air-conditioning." UNEP Ozone Secretariat Workshop on
HFC management: technical issues. Bangkok, 20 and 21 April 2015. Available
online at: http://ozone.unep.org/sites/ozone/files/Meeting Documents/HFCs/
FS 10 Water chillers for air-conditioning Oct 2015.pdf
United Nations Industrial Development Organization (UNIDO). Demonstrating
the Feasibility of R-290 Based AC Manufacturing: China's Midea and Meizhi
Case. OzonAction Fact Sheet. Available online at: http://www.unep.org/
ozonaction/Portals/105/documents/events/MQP26/Fact%20Sheet%20
UNI D0%20Meizhi%20Nov%2013.pdf.
United States Environmental Protection Agency (U.S. EPA). 2010a. "Federal
Register Vol. 75, No. 115." Available online at: https://www.gpo.gov/fdsvs/
pkg/FR-2010-06-16/pdf/2010-14510.pdf
United States Environmental Protection Agency (U.S. EPA). 2010b. "Summary
of Substitute Refrigerants Listed in SNAP Notice 25." Available online
at: http://www2.epa.gov/sites/production/files/2014-11/documents/
notice25substituterefrigerants.pdf
United States Environmental Protection Agency (U.S. EPA). 2011. "Federal
Register Vol. 76, No. 60." Available online at: http://www.gpo.gov/fdsvs/pkg/
FR-2011-03-29/pdf/2011 -6268.pdf
United States Environmental Protection Agency (U.S. EPA). 2012. "Federal
Register Vol. 77, No. 155." Available online at: http://www.gpo.gov/fdsvs/pkg/
FR-2012-08-10/pdf/2012-19688.pdf
United States Environmental Protection Agency (U.S. EPA). 2013. "Global
Mitigation of Non-CO, Greenhouse Gases: 2010-2030." EPA Report 430-
R-13-011. September 2013. Available online at: https://www3.epa.gov/
climatechange/Downloads/EPAactivities/MAC Report 2013.pdf
United States Environmental Protection Agency (U.S. EPA). 2014. "Federal
Register Vol. 79, No. 203." Available online at: http://www.gpo.gov/fdsvs/pkg/
FR-2014-10-21/pdf/2014-24989.pdf
United States Environmental Protection Agency (U.S. EPA). 2015a. "Federal
Register Vol. 80, No. 136." Available online at: http://www.gpo.gov/fdsvs/pkg/
FR-2015-07-16/pdf/2015-17469.pdf
United States Environmental Protection Agency (U.S. EPA). 2015b. "Federal
Register Vol. 80 No. 69." Available online at: http://www.gpo.gov/fdsvs/pkg/
FR-2015-04-10/pdf/2015-07895.pdf
United States Environmental Protection Agency (U.S. EPA). 2015c. "Substitutes
by Sector." Significant New Alternatives Policy (SNAP) Program. Available
online at: http://www.epa.gov/snap/substitutes-sector
United States Environmental Protection Agency (U.S. EPA). 2015d.
"Transitioning to Low-GWP Alternatives in Residential & Light Commercial
Air Conditioning." Available online at: http://www.epa.gov/sites/production/
files/2015-09/documents/epa hfc residential light commercial ac.pdf
Velders, G.J.M., D.W. Fahey, J.S. Daniel, S.O. Andersen, and M. McFarland.
2015. Future atmospheric abundances and climate forcings from scenarios
of global and regional hydrofluorocarbon (HFC) emissions. Atmospheric
Environment. Volume 123, Part A. December 2015. Available online at:
http://dx.doi.Org/10.1016/i.atmosenv.2015.10.071.
SNAP
SIGNIFICANT NEW ALTERNATIVES POLICY
PRO^°
EPA-430-F-15-028 • www.epa.gov • December 2016

-------