*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 1 of 58 **EO 12866_SNAP_CO2MVA C**  **- RIN2060_AM54_FINAL_RULE_20120405**  **.docx ENVIRONMENTAL PROTECTION AGENCY**  **40 CFR Part 8 2**  **[** EPA - HQ - OAR - 2 004 - 0488 **; FRL -** **XXXX -** **X ]**  [RIN 20 60 - AM54 ] Protection of S tratospheric Ozone: Alternative for the Motor Vehicle Air Conditioning Sector under the Significant New Alternatives Policy (SNAP) Program **AGENCY:** Environmental Protection Agency (EPA) **ACTION:** Final Rule

---------------------------------------------------------------------------------- ----------------------------------- **SUMMARY** : Pursuant to the U.S. Environmental Protection Agency (EPA)’s Significant New Alternatives Policy

(SNAP) program, this action lists carbon dioxide (CO 2 ) or R - 744, as acceptable substitute , subject to use conditions, in the motor vehicle air conditioning (MVAC) end - use for motor vehicles (i.e., passenger cars, light - duty and heavy- duty vehicles) within the refrigeration and air- conditioning sector. This final rule only concerns the use of C O 2 in MVAC sy stems designed specifically for the use of CO 2 refrigerant . The substitute is non - ozone depleting and therefore does not contribute to stratospheric ozone depletion. **DATES:** This final rule is effective on [I NSERT 6 0 DAYS FROM DATE OF PUBLICATION INTHE FEDERAL REGI STER]. **ADDRESSES:** EPA has established a docket for this action under Docket ID No . EPA - HQ OAR - 2 004 - 0488. All documents in the docket are listed on the www.regulations.gov web site. Although listed in the index, some information is not publicly available, e.g., confidential business information ( CBI) or other information whose disclosure is restricted by statute. Certain*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 2 of 58 other material, such as copy righted material, is not placed on the Internet and will be publicly available onl y in hard copy form. Publicly

available docket materials are available either electronically

through www.regulations.gov or in hard copy from the EPA Air and Radiation Doc ket, EPA/DC, EPA West, Room 3334 , 1301 Constitution Ave., NW, Washington, DC. This Public Reading Room i s open from 8:30 a.m. to 4:30 p.m., Monday through Friday , excluding legal holiday s. The telephone number for the Public Reading Room is (202) 566 - 1744, and the telephone number for the Air and Radiation Docket is ( 2 02) 566 - 174 2 . **FOR FURTHER INFORMATION CONTACT:** Yaidi Cancel , Stratospheric Protection Division, Office of Air and Radiation, MC 6 2 05J, Environmental Protection Agency, 1 2 00 Pennsylvania Ave ., NW, Washington, DC 2 0460; t elephone number: ( 2 0 2 ) 343 - 951 2 ; fax number: ( 2 0 2 ) 343 - 2 338 ; email address: cancel. ya idi @epa.gov. **SUPP LEMENTARY INFORMATION:**  This final action provides motor vehicle manufacturers and their suppliers with a refrigerant option subject to use conditions for motor vehicle air conditioning sy stems for use in new vehicles

. The refrigerant discussed in this action , carbon dioxide (R- 744, CO 2 ) is non ozone - depleting and has a global warming potential (GWP) 1 of 1. **TABLE OF CONTENTS** I. Does this action appl y to me? II. What abbreviations and acronym s are used in this action? III. How does the SNAP program work? A. What are the statutory requirements and authority for the SNAP program?

1 GWP, is defined as the ratio of heat trapped by one unit mass of the greenhouse gas to that of one unit mass of CO 2 over a over a specified period of time. Consistent with the international standards under the United Nations Framework Convention on Climate Change (UNFCCC), all GWPs in this rule are given using a 100 - year period ( IPCC, 1996 ) .*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 3 of 58 B. What are EPA's regulations implementing section 612 of the Clean Air Act ? C. How do the regulations for the SNAP program work? D. Where can I get additional information about the SNAP program? IV . What is EPA's f

inal d ecision for CO 2 as an alternative for MVAC? V. Why is EP A establishing these final use conditions for the use of CO 2 in MVAC ? , VI . Why is EPA listing CO 2 acceptable subject to use conditions? VII. What is the relationship between this SNAP rule and other EPA rules? VI I I . What is EPA's response to public comments on the proposal? A. Use c onditions B. Risk m itigation s trategies C. Industry s tandard s D . Servicing IX . Statutory

and e xecutive o rder r eviews A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improvi ng Regulation and Regulatory Review B. Paperwork Reduction Act C. Regulatory

Flexibility

Act D. Unfunded Mandates Reform Act E. Executive Order 13132: Federalism F. Executive O rder 13175: Constitution and Coordination with Indian Tribal Governments G. Executive O rder 13045: Protection of Children from Environmental Health Risks and Safety Risks H. Executive O rder 13211: Actions that Significantly Affect Energy

Supply , Distribution, or Use*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 4 of 58 I. National Technology

Transfer Advancement Act K. Congression al Review Act X . References **I. Does This Action Apply to Me?**  This final rule lists carbon dioxide (CO 2 ) 2 , also known as R - 744, as an acceptable substitute subject to use conditions for use as a refrigerant in new motor vehicle air conditioning (MVAC) sy stems designed specifically for the use of CO 2 refrigerant in motor vehicles 3 . Businesses in this end - use that may want to use CO 2 in MVAC systems include:

 m otor vehicle manufacturers

 motor vehic le air conditioning service and repair shops Regulated entities may

include: Table 1

–

Potentially Regulated Entities, by North American Industrial Classification System (NAICS) Code Category NAI CS code Description of regulated entities Industry 336111 , 336 112, 336120 Motor Vehicle Manufacturing Services 8111 98 Vehicle Air Conditioning Repair This table is not intended to be exhaustive, but rather a guide regarding entities likely to be regulated b y this action. If you have any questions about whether this action applies to a particular entity , consult the person listed in the preceding section, “FOR FURTHER IN FORMAT ION CONTACT.”

2 Chemical Abstracts Servic e [CAS] Registry: No. 124 - 38 - 9 3 This final action applies only to air conditioning systems in motor vehicles consistent with the definition of light duty vehicles and heavy - duty vehicles under 40 CFR §86.1803 - 01, with the exception of passenger busses .*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 5 of 58 **II. What abbreviations and acronyms are used in this action?**  ACGIH - American Conference of Governmental Industrial Hygienists ASE-National Institute for Automotive Service Excellence CAA - Clean Air Act CAS - Chemical Abstracts Service CBI - confidential business information CFC- chlorofluorocarbon CFC - 12 - the chemical dichlorodifluoromethane, CAS Reg. No. 75 - 71 - 8 CFD - computational fluid dy namics CFR - Code of Federal Regulations CNS

– central nervous s ystem CO2 - carbon dioxide, CAS Reg. No. 124 - 38 - 9, also known as R - 744 CRP- Cooperative Research Program EPA - the United States Environmental Protection Agency EO - Executive Order FMEA - Failure Mode and Effect Anal ys is FR - Federal Register FTA - fault - tree anal ys is GW P- Global warming potential HCFC - 22

– the chemical chlorodifluoromethane, CAS Reg No. 75 - 45 - 6 HCFC - 142b

– the chemical 1 - chloro - 1,1 - difluoroethane, CAS Reg No. 75 - 68 - 3 HFC - hydrofluorocarbon HFC - 134a - the chemical 1,1,1,2 - tetrafluoroethane, CAS Reg. No. 811 - 97 - 2*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 6 of 58 HFC - 152a - the chemical 1,1 - difluoroethane, CAS Reg. No. 75 - 37 - 6 HFO- hydrofluoroolefin HFO- 1234yf

- the chemical 2,3,3,3 - tetrafluoroprop - 1 - ene, CAS Reg. No. 754 - 12 - 1 IDLH - Immediatel y Dangerous to Life and Health MVAC- motor vehicle air conditioning NIOSH -National Institute for Occupational Safety and Health NODA - Announcement of Data Availability , formerly known as Notice of Data Availability NPRM -Notice of Proposed Rulemaking NTTAA -National Technology Transfer and Advancement Act ODP- ozone depletion potential ODS - ozone - depleting substance OEM - original equipment manufacturer OMB - the United States Office of Management and Budget OSHA - the United States Occupational Safety and Health Administration PEL - Permissible Expos ure Level p p m -parts per million RDECOM

- U.S. Army Research, Development and Engineering Command REL - Recommended Exposure Level RFA - Regulatory

Flexibility

Act SAE- SAE International, formerl y the Society of Automotive Engineers SAE CRP- SAE Cooperative Research Program SBREFA - Small Business Regulatory Enforcement Fairness Act SNAP- Significant New Alternatives Policy*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 7 of 58 STEL - Short Term Exposure Limit TW A - Time Weighted Average UMRA - Unfunded Mandates Reform Act **III. How does the SNAP program work?**  A. What are the statutory requirements and authority for the SNAP program? Section 612 of the Clean Air Act ( CAA) requires U.S. Environmental Protection Agency ( EPA) to develop a program for evaluating alternatives to ozone - depleting substances (ODS) . EPA refers to this program as the Significant New Alternatives Policy (SNAP) program. The major provisions of section 61 2 are: 1. Rulemaking Section 612(c) requires EPA to promulgate rules making it unlawful to replace any class I ( i. e., chlorofluorocarbon, halon, carbon tetrachloride, methyl chloroform, methyl bromide, and hydrobromofluorocarbon) or class II ( i.e., hydrochlorofluorocarbon) substance with any substitute that the Administrator determines may present adverse effects to human health or the environment where the Administrator has identified an alternative that (1) reduces the overall risk to human health and the environment, and (2) is currentl y or potentiall y available. 2. Li sting of Unacceptable/Acceptable Substitutes Sec tion 61 2 (c) requires EPA to publish a list of the substitutes unacceptable for specific uses and to publish a corresponding list of acceptable alternatives for specific uses. The list of acc eptable substitutes is found at http://www.epa.gov/ozone/snap/list s/index.html and the lists of “unacceptable , ” “acceptable subject to use conditions , ” and “acceptable subject to narrowed use limits” substitutes are found in the appendices to 40 CFR part 82 subpart G.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 8 of 58 3. Petition Process Section 61 2 (d) grants the right to any person to petition EPA to add a substance , add or delete use restrictions , or delete a substance from the lists published in accordance with section 61 2 (c). The Agency

has 90 day s to grant or deny a petition. Where the Agency grants the petition, EPA must publish the revised lists within an additional six months. 4. 90 - day Notification Section 61 2 (e) directs EPA to require any person who produces a chemical substitute for a class I substance to notify the Agency

not less than 90 day s before new or existing chemicals are introduced into interstate commerce for significant new uses as substitutes for a class I substance. The producer must also provide the Agency with the producer's unpublished health and safety studies on such substitutes. 5. Outreach Section 61 2 (b)(1) states that the Administrator shall seek to maximize the use of federal research facilities and resources to assist users of class Iand II substances in identifying and developing alternatives to the use of such substances in key commercial applications. 6. Clearinghouse Section 61 2 (b)(4) requires the Agency to set up a public clearinghouse of alternative chemicals, product substitutes, and alternative manufacturing processes that are available for products and manufacturing processes which use class Iand II substances. B. What are EPA’s regulations implementing section 612? On March 18, 1994, EPA published the original rulemaking (59 FR 13044) which established the process for administering the SNAP program and issued EPA's first lists*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 9 of 58 identifying acceptable and unacceptable substitutes in the major industrial use sectors (40 CFR part 82, subpart G). These sectors include: refrigeration and air conditioning; foam blowing; solvents cleaning; fire suppression and explosion protection ; sterilants; aerosols; adhesives, coatings and inks; and tobacco expansion. These sectors compri se the principal industrial sectors that historically

consumed the largest volumes of ODS . Section 612 of the CAA requires EPA to list as acceptable those subs titutes that do not present a significantly

greater risk to human health and the environment as compared with other substitutes that are currently or potentiall y available. C. How do the regulations for the SNAP program work? Under the SNAP regulations , anyone who produce s a substitute to replace a class I or II ODS in one of the eight major industrial use sectors must provide notice to the Agency , including health and safety information on the substitute at least 90 days before introducing it into interstate commerce for significant new use as an alternative. 40 CFR 82.176(a). This requirement applies to the person planning to introduce the substitute into interstate commerce, 4 ty picall y chemical manufacturers, but may also include importers, formulator s, equipment manufacturers, or end - users 5 when they are responsible for introducing a substitute into commerce. The 90 - day

SNAP review process begins once EPA receives the submission and determines that the submission includes complete and adequate da ta. 40 CFR 82.180(a). The CAA and the SNAP regulations, 40 CFR 82.174(a), prohibit use of a substitute earlier than 90 -

**4** As defined at 40 CFR 82.104 “interstate commerce” means the distribution or transportation of any product between one state, territory, possession or the District of Columbia, and another state, territory, possession or the District of Columbia, or the sale, use or manufacture of any product in more than one state, territory, possession or District of Columbia. The entry points for which a product is introduced into interstate commerce are the release of a product from the facility in which the product was manufactured, the entry into a warehouse from which the domestic manufacturer releases the product for sale or distribution, and at the site of United States Customs clearance. 5 As defined at 40 CFR 82.17 2 “end - use” means processes or classes of speci fic applications within major industrial sectors where a substitute is used to replace an ozone - depleting substance.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 10 of 58 day s after notice has been provided to the Agency. The Agency

has identified four possible decision categories for substitutes: acceptable; acceptable subject to use conditions; acceptable subject to narrowed use limits; and unacceptable. 6 40 CFR 82.180(b). Use conditions and narrowed use limits are both considered “use restrictions” and are explained below. Substitutes that are deemed acceptab le with no use restrictions (no use conditions or narrowed use limits) can be used for all applications within the relevant end - uses within the sector. Substitutes that are acceptable subject to use restrictions may be used onl y in accordance with those re strictions. After reviewing a substitute, the Agency may determine that a substitute is acceptable only if certain conditions in the way that the substitute is used are met to minimize risks to human health and the environment. EPA describes such substitutes as "acceptable subject to use conditions." Entities that use these substitutes without meeting the associated use conditions are in violation of section 612 of the Clean Air Act and EPA’s SNAP regulations. 40 CF 82.174(c). For some substitutes, the Ag ency may permit a narrow range of use within an end - use or sector. For example, the Agency may limit the use of a substitute to certain end - uses or specific applications within an industry sector. The Agency

requires a user of a narrowed use substitute to demonstrate that no other acceptable substitutes are available for their specific application b y conducting comprehensive studies. EPA describes these substitutes as “acceptable subject to narrowed use limits.” A person using a substitute that is acceptabl e subject to narrowed use limits in applications and end - uses that are not consistent with the narrowed use limit is using these substitutes in an unacceptable manner and is in violation of section 612 of the CAA and EPA’s SNAP regulations. 40 CFR 82.174(c ).

6 The SNAP regulations also include “pending,” referring to submissions for which EPA has not reached a determination, under this provisio n.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 11 of 58 The Agency

publishes its SNAP program decisions in the Federal Register (FR). EPA publishes decisions concerning substitutes that are deemed acceptable subject to use restrictions (use conditions and/or narrowed use limits), or for substitutes deemed unacceptable, as proposed rulemakings to allow the public opportunity to comment, before publishing final decisions. In contrast, EPA publishes substitutes that are deemed acceptable with no restrictions in “notices of acceptability ,” rather than as proposed and final rules. As described in the preamble to the rule initially

impl ementing the SNAP program (59 FR 13044 ; March 18, 1994 ) ), EPA does not believe that rulemaking procedures are necessary to list alternatives that are acceptable without restrictions because such listings neither impose any sanction nor prevent anyone from using a substitute. Many SNAP listings include “comments” or “further information” to provide additional information on substitutes. Since this additional information is not part of the regulatory decision, these statements are not binding for use of the substitute under the SNAP program. However, regulatory

requirements so listed are binding under other regulatory programs. The “further information” classification does not necessarily include all other legal obligations pertaining to the use of the substi tute. While the items listed are not legally binding under the SNAP program, EPA encourages users of substitutes to apply all statements in the “further information” column in their use of these substitutes. In many instances, the information simply refers to sound operating practices that have already been identified in existing industry and/or building - codes or standards. Thus, many of the statements, if adopted, would not require the affected user to make significant changes in existing operating practic es. D. Where can I get additional information about the SNAP program? For copies of the comprehensive SNAP lists of substitutes or additional information on*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 12 of 58 SNAP, refer to EPA’s Ozone Depletion web site at www.epa.gov/ozone/snap/index.html. For more inf ormation on the Agency's process for administering the SNAP program or criteria for evaluation of substitutes, refer to the SNAP final rulemaking published March 18, 1994 (59 FR 13044), codified at 40 CFR part 82, subpart G. A complete chronology of SNAP d ecisions and the appropriate citations are found at http://www.epa.gov/ozone/snap/chron.html . **IV. What is EPA's final decision for CO**  **2 as an alternative for MVAC?** 

In this final rule, EPA is modifying its previous determination that listed CO 2 a s an acceptable substitute for CFC - 12 in new MVAC sy stems ( 59 FR 13044 ; March 18, 1994 ) and is listing CO 2 acceptable, subject to use conditions, as a substitute for CFC - 12 in new MVAC sy stems . This final action does not apply to the use of CO 2 as a conversion or retrofit for existing MVAC sy stems. In addition, it does not apply to the use of CO 2 in the air conditioning or refrigeration s ys tems of buses , trains, rail or subway cars, or appliances such as refrigerated transport . Th is refrigerant may be used only

in equipment designed specifically and clearl y identified for this refrigerant (i.e., it may not be used as a conversion or “retrofit” refrigerant for existing equipment). EPA is not mandating the use of CO 2 or any other alternative to ODS in MVAC sy stems. Vehicle m anufacturers have the option of using any refrigerant listed as acceptable for this end - use, so long as they meet the applicable use conditions. This action removes CO 2 from the list of acceptable substitutes for MVAC s ys tems and instead li sts it as acceptable subject to the following use conditions: 1. Engineering strategies and /or mitigation devices shall be incorporated such that in the event of refrigerant leak s the resulting CO 2 concentrations do not exceed:

 The short term exposure level (STEL) of 3% or 30,000 ppm averaged over 15 minutes in the passenger free space ; and*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 13 of 58  The ceiling limit of 4% or 40,000 ppm in the passenger breathing zone . 2. Vehicle manufacturers (i.e., original equipment manufacturers [OEMs]) must keep records of the tests performed for a minimum period of three ye ars demonstrating that CO 2 refrigerant levels do not exceed the STEL of 3% averaged over 15 minutes in the passen ger free space, and the ceiling limit of 4% in the breathing zone. 3. The use of CO 2 in MVAC sy stems must adhere to the standard conditions identified in SAE 7 Standard J639 (2011 version) including :  Installation of a high pressure system warning label;

 Installation of a compressor cut - off switch 8 ; and

 U se of unique fittings with : i. O utside diameter of 16.6 +0/ - 0.2 mm (0.6535 +0/ - 0.0078 inches) for the MVAC low - side service port ; ii. Outside diameter of 18.1 +0/ - 0.2 mm (0.7126 +0/ - 0.0078 inches) for the MVAC high - side service port ; and iii. O utside diameter of 20.955 +0/ - 0.127 mm ( 0.825 +0/ - 0.005 inches ) and right - hand thread direction for C O 2 refrigerant service container s 9

. To help ensure that the first use condition is met, we are including several recommendations in the listing decision. First, OEMs should conduct and keep on file Failure

7 SAE International, formerly the Society of Automotive Engineers . 8 A compressor cut - off switch causes a device to stop compressor operation before activation of any pressure relief device. **9** The refrigerant service containers fitting requirement applies only to refrigerant service containers used during servicing of the MVAC, in accordance with the provisions established for MVAC servicing under 40 CFR part 82, subpart B .*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 14 of 58 Mode and Effect Analysis ( FMEA) on the MVAC as stated in SAE J1739 (Potential Failure Mode and Effects Analy sis in Design [Design FMEA], Potential Failure Mode and Effect Analy sis in Manufacturing and Assembly Process [Process FMEA]) , or equivalent. Second , OEMs should factor in background CO 2 concentrations that come about from no r mal respiration by the maximum number of vehicle occupants. 10 Third, EPA reco mmends the use of the following industry

standards as additional references wh en locating the driver’s and passengers’ breathing zone consistent with the head and seating position, measuring refrigerant concentrations at different locations in side the passenger compartment including the breathing zone, and addressing risks associated with MVAC use:

 SAE J1052 - Motor Vehicle Driver and Passenger Head Position;

 SAE J2772 - Measurement of Passenger Compartment Refrigerant Concentrations under Sy stem Refrigerant L eakage Conditions; and

 SAE J2773 - Standard for Refrigerant Risk Analy sis for Mobile Air Conditioning Sy stems . Fourth, EPA recommends additional training for MVAC ser vice technicians that will service MVAC s ys tems using CO 2 as the refrigerant . **V. Why is EPA**  **establishing these final use conditions**  **for the use of CO**  **2 in**  **new MVAC**  **?** Summary of SNAP actions on the use of CO2 as a refrigerant in MVAC In the initial SNAP rulemaking issued on March 18, 1994 (59 FR 13044), EPA found CO 2 acceptable as a substitute for CFC - 12 in new MVAC sy stems . In that final rule, EPA also found other substitutes (i.e . , HFC - 134a and R - 401C, evaporative cooling and stirring cycle)

**10** Maximum number of vehicle occupants include s the maximum number of passeng ers in a normal seating position inside the passenger compartment . This may vary between vehicle types .*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 15 of 58 acceptable for use in new MVAC sy stems . On June 13, 1995 (60 FR 31092) and October 16, 1996 (61 FR 54040) EPA took two separate actions requiring the use of unique fittings for several refrigerants then currentl y listed as acceptable for use in new MVAC sy stems (60 F R 31092) and for refrigerants subsequently found acceptable for use in MVAC ( 61 FR 54040 ). The use conditions requiring unique fittings were codified at 40 CFR Part 82, Subpart G, Appendix D. N one of these actions applied to CO 2 . However, in th e preamble to the October 16, 1996 SNAP rule, EPA stated that for any decision made under SNAP, the Agency may , on its own, determine that additional conditions or restrictions should be added or removed through future rulemaking (61 FR 54032). Also, EPA stated in the October 16, 1996 SNAP rule that due concerns about potential cross - contamination as a result of the large number of MVAC refrigerants, the Agency

may choose to list a substitute as acceptable subject to use the conditions listed (in that rule, i.e., use of unique fittings) while proceeding with notice - and comment rulemaking to impose other restrictions (61 FR 54034). Although the initial SNAP rulemaking listed CO 2 as acceptable for use in new MVAC sy stems, at that time, EPA was not aware of any interest in using CO 2 in MVAC sy stems and did not receive any submission for unique fittings to be used on CO 2 MVAC sy stems or any information specified in 40 CFR Part 82, Subpart G, Appendix D . EPA was subsequently made aware through risk screens of concerns regarding health risks to exposure of CO 2 from refrigerant leaks into the passenger compartment (EPA - HQ - OAR - 2004 - 0488 - 0025.2). EPA was also made aware of potential interest in using CO 2 as a refrigerant for MVAC sy stems and of technology

being developed ( 71 FR 55141; September 21, 2006 ) . O n September 21, 2006 , we issued a Notice of Proposed Rulemaking (referred to hereinafter as “the proposal” or NPRM) proposing to find CO 2 acceptable as a substitute for CFC - 12 in new MVAC sy stems , subject to*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 16 of 58 the use conditions specified at 40 CFR Part 82, Subpart G, Appendix D (71 FR 55140) . In addition, due to concerns regarding the possibility of driver performance decrement and adverse effects on passengers if exposed to concentrations of CO 2 above 3% during a short period of time (e.g., 15 minutes), we proposed use conditions restricting CO 2 refrigerant concentrations to a STELof 3% averaged over 15 minutes in the passenger free space caused by leaks from the MVAC. **11** Subsequently , on September 17, 2009 (74 FR 47774) , EPA issued a n otice of data availability

(NODA) making available to the public additional information received supporting a ceiling limit of 4% CO 2 as a level that should not be exceeded for any period of time due to possible adverse health effects. We also requested public comment on whether EPA should include in a final rule , listing CO 2 as acceptable subject to use conditions for new MVAC sy stems , a ceiling limit of 4% CO 2 in addition to the proposed STEL of 3% averaged over 15 minutes inside the passenger compartment, and whether the proposed use conditions should apply when the ignition is off. Basis for use conditions included in this final rule EPA proposed three use conditions in the NPRM. One use condition required that sy stems be designed to avoid occupant exposure to CO 2 concentrations above a STEL of 3% CO 2 averaged over 15 minutes in the passenger free space , during the event of a leak . The passenger free space is the space inside the passenger compartment excluding the space enclosed by the ducting in the HVAC module (71 FR 55149). The proposal also stated that a breathing zone ceiling limit may

provide additional assurance regarding vehicle driver alertness and requested comment on whether a maximum limit should be applied in the driver and passenger breathing zone, in addition to the 3% CO 2 free space lim it averaged over 15 minutes. In the

11 In the same NPRM, EPA also proposed to find HFC - 152a acceptable subject to use conditions. On June 12, 2008, EPA published a final rule listing HFC - 15 2a as an acceptable substitute , subject to use conditions, for new MVAC (73 FR 33304), but deferred final ruling on the use of CO 2 in new MVAC systems.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 17 of 58 NODA , we defined the breathing zone as the space where p eople breathe (74 FR 47775) , and data received during the public comment period defined this zone as the area inside the passenger compartment where the driver’s an d passengers’ heads are located during a normal sitting position. 12 The other proposed use conditions required OEMs to: 1) keep records of the test performed to ensure that MVAC sy stems are safe and designed with sufficient safety mitigation devices so that occupants are not exposed to levels above the CO 2 STEL ; and 2) adhere to all the safety requirements listed in the SAE Standard J639, in addition to the use conditions already established under Appendix D to Subpart G of 40 CFR Part 82 , for MVAC substitutes: unique fittings **13** , label, and a compressor cut - off switch. We received a number of public comments on the proposed use conditions and subsequent data announced in the NODA regarding the 4% CO 2 ceiling limit. Some commenters claimed that the proposed STELof 3% CO 2 averaged over 15 minutes was enough to protect passengers and ensure driver alertness (EPA - HQ - OAR - 2004 - 0448 - 0025.1, - 0032, - 0044). Other commenters stated that there are sufficient arguments for choosing percent concentration limits higher than the proposed STELof 3% CO 2 averaged over 15 minutes (EPA - HQ - OAR - 2004 - 0448 - 0043, - 0049). Alternatively , some commenters requested a maximum CO 2 ceiling limit in the passenger breathing zone (EPA - HQ - OAR - 2004 - 0448 - 0030, - 0035, - 0047.1) and one commenter considered appropriate the 4% CO 2 ceiling limit as an additional use condition (EPA HQ - OAR - 2004 - 0448 - 0047.1). After considering the information in the docket at the time of proposal, comments

12 This was the location considered in the U.S. Army risk assessment, in addition to the rest of the ve hicle occupant compartment (EPA - HQ - OAR - 2004 - 0488 - 0025.2) 13 The unique fittings provision applies for MVAC service ports and co ntainers intended for servicing of the MVAC (Appendix D to Subpart G of 40 CFR Part 82, 61 FR 54040; October 16, 2006).*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 18 of 58 received on the proposed rule, and additional information we have received in response to the NODA, we have decided to finalize the use conditions as proposed in the September 21, 2006, NPRM, and to add a ceiling limit of 4% CO 2 , which would apply in addition to the 3% averaged over 15 - minute CO 2 STEL. We believe that requiring a CO 2 ceiling limit is necessary because it is possible for a time - weighted average concentration, such as the STEL , to be under 3%, while peak concentrations could reach higher limits resulting in possible hearing and vision effects that could distract and endanger a driver, or cause other, potentially more severe adverse health effects ( EPA - HQ - OAR - 2004 - 0488 - 0041 ). Thus, the proposed use condition requiring mitigation strategies for MVAC sy stems, to prevent leaks of CO 2 refrigerant reaching concentrations above 3% averaged over 15 minutes inside the passenger compartment free space, may not be sufficient on its own to protect drivers and passengers. This further protective limit is necessary to ensure that overall ri sks to human health and the environment from CO 2 will be similar to or less than those of other available refrigerants that EPA has already listed as acceptable for MVAC. In the final rule, we also revised the proposed use condition on recordkeeping to refer to the 4% ceiling limit. The September 21, 2006 NPRM proposed requiring OEMs to keep records demonstrating they

have met the use condition requiring safety mitigation devices to avoid occupant exposure above the 3% CO 2 STELin the passenger compartment. The final use condition addressing recordkeeping requires OEMs to keep records of the tests performed for a minimum period of three years demonstrating that MVAC sy stems are designed incorporating engineering devices or mitigation strategies so that in the event of refrigerant leak, the resulting concentrations of CO 2 in the passenger free space do not exceed the STEL of 3% averaged over 15 minutes and do not exceed the c eiling limit of 4% in the passenger breathing zone. Keeping records of tests performed evaluating system safety is a customary

practice for OEMs while*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 19 of 58 vehicles are in production and for several ye ars afterward (EPA - HQ - OAR - 2004 - 0488 - 0057). For purposes of the final rule, we are referencing to the 2011 version of SAE J 639 instead of the 2005 version referenced in the proposed rule. The SAE J639 2011 version added new provisions designed specifically to address use of another refrigerant, HFO - 1234yf (EPA - HQ OAR - 2004 - 0488 - 0059). The provisions under the 2011 version of SAE J639 for h igh pressure sy stem warning label, compressor cut - off switch , and unique fittings , remain unchanged. C onsistent with the proposed rule , the criteria for uniqueness of fittings under Appendix H to S ubpart G of 40 CFR Part 82, and the provisions of Appendix D to Subpart G of 40 CFR Part 82 and SAE J639 (2011 version), in this final rule we specify that the CO 2 refrigerant fitting s must have: 1) an o utside diameter of 16.6 +0/ - 0.2 mm (0.6535 +0/ - 0.0078 inches) for the MVAC low side, 2) an o utside diameter of 18.1 +0/ - 0.2 mm (0.7126 +0/ - 0.0078 inches) for the MVAC high side, and 3) an o utside diameter of 20.955 +0/ - 0.127 mm (0.825 +0/ - 0.005 inches) and right - hand thread direction for refrigerant service containers . 14 Wh y is EPA listing CO2 acceptable subject to use conditions? EPA is listing CO 2 acceptable subject to use conditions because the use conditions are necessary to ensure that use of CO 2 will not present greater risk to human health and the environment than other available substitutes acceptable for use in new MVAC sy stems . Examples of other substitutes that EPA has already found acceptable subject to use conditions for use in new MVAC systems include HFC - 152a and HFO - 1234yf. 15 A list of acceptable substitutes subject to use conditions for use in new MVAC sy stems can be found at Appendix B 14 The SAE J639 standard specifies unique fittings for high - side and low- side service ports and makes reference to SAE J2683 “Refrigerant Purity and Container requirements for Carbon Dioxide (CO 2 R- 744) Used in Mobile Air Conditioning Systems” which specifies that the unique fitting for CO 2 refrigerant service containers must be consistent with the Cylinder Gas Association’s fitting CGA 320 (for 0 - 3000 psi) w hich has an outside diameter of 0.825 +0/ - 0.005 inches (20.955 +0/ - 0.127 mm) and right - hand thread direction (EPA - HQ - OAR - 2004 - 0488 - 0059, - 0060). 15 HFO - 1234yf was found acceptable only for MVAC systems in new passenger cars and light duty trucks ( 76 FR 17488, March 29, 2011).*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 20 of 58 to Subpart G of 40 CFR, Part 82 and http://www.epa.gov/ozone/snap/refrigerants/lists/mvacs.html . EPA is requiring the use of unique fittings for CO 2 refrigerant consistent with Appendix D to Subpart G of 40 CFR P art 82 (61 FR 54040 ; October 16, 1996). A ll acceptable substitutes for use in MVAC sy stems are subject to thos e use conditions ( and thus are identified as acceptable subject to use conditions ) . For CO 2 , the unique fittings that must be used for MVAC sy stems are those identified in the industry standard SAE J639 (2011 version) . In addition to the use conditions regarding unique fittings, EPA is requiring OEMs to adhere to all the safety requirements of SAE J639 (2011 version) for the safe design of new MVAC sy stems using CO 2 . We are establishing this as a use condition to ensure that new MVAC sy stems that use CO 2 are specificall y designed to minimize release of the refrigerant into the passenger cabin . A dherence to the standard will minimize the risk s that CO 2 refrigerant levels in the passenger compartment and breathing zone would exceed the CO 2 limits of 3% averaged over 15 minutes in the passenger cabin free space and the 4% ceiling limit in the passenger breathing zone. Environmental impacts EPA finds that CO 2 does not pose greater risk to the environment than other substitutes that are currentl y available in the end - use being evaluated in this rulemaking . In at least one aspect, CO 2 is significantly

better for the environment than most alternatives currently listed as acceptable subject to use conditions in the MVAC end - use . CO 2 has a hundred - ye ar time horizon (100 - yr) global warming potential (GWP) of one, c ompared with a GWP of four for HFO - 1234yf, 124 for HFC - 152a, and 1 , 430 for HFC - 134a. Further, CO 2 has an ozone depletion potential (ODP) of zero, comparable to HFO - 1234yf, HFC - 152a, and HFC - 134a. Other SNAP - approved refrigerant blends*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 21 of 58 containing HCFCs have ODP s ranging from 0.065 to 0.022 . Additionally, CO 2 is excluded from the definition of volatile organic compound (VOC) under CAA regulations (see 40 CFR 51.100(s)). Human health and safety impacts Carbon dioxide is not flammable, similar to HFC - 134a and most other acceptable alternatives for MVACs. Therefore, it does not add risks of fire in a vehicle when used. For the MVAC end - use, the EPA has listed two flammable alternatives (HFC - 152a and HFO - 1234yf) acceptable, subject to use conditions to mitigate flammability risks. CO 2 is an asphy

xiant that obstructs the oxygen flow into the body (OSHA, 1996; as cited in EPA - HQ - OAR - 2004 - 0488 - 0041). However, it is not the only gas that may

cause asphy

xia. Releasing almost any

gas 16 into an unventilated or poorly ventilated space can lower the oxygen concentration to a level that poses significant he alth risk s (EPA - HQ - OAR - 2004 - 0488 - 0041). Health risks could occur to drivers or vehicle occupants during release of CO 2 refrigerant into the passenger compartment. Additionally , occupational risks could occur during the manufacture of the refrigerant, initial installation of the refrigerant into the MVAC sy stem at the vehicle assembly plant, servicing of the MVAC sy stem, or final dispo sition of the MVAC sy stem (i.e., recycling or disposal). We evaluated potential human health and safety i mpacts , including the short - and long term toxicity

of CO 2 and risk of injury to service personnel from high - pressure CO 2 MVAC sy stems , and considered detailed risk assessments with fault - tree anal ys is (FTA), (EPA - HQ OAR - 2004 - 0488 - 0017, - 0022, and - 0025.2), scientific data provided in public comments (EPA HQ - OAR - 2004 - 0488 - 0037.1) and other information obtained during the notice of data

16 Any refrigerant can act as an asphyxiant by limiting available oxygen in a space. When oxygen levels in air are reduced to 12 - 14% by displacement, symptoms of asphyxiation, loss of concentration, increased pulse rate and deeper respiration will occur.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 22 of 58 availability (EPA - HQ - OAR - 2004 - 0488 - 0041). W e also reviewed a risk assessment with fault tree analy sis from the SAE Corporate Research Program (CRP) for HFO - 1234yf and CO 2 , submitted during the public comment period for another SNAP rulemaking 17 (EPA - HQ - OAR 2004 - 0488 - 0051, E PA - HQ - OAR - 2008 - 0664 - 0008, and - 0056). We also evaluated and provided additional information on the health effects and risks to CO 2 exposure through a contractorauthored report “ Review of Health Impacts from Short - Term Carbon Dioxide Inhalation Exposures ” (EPA - HQ - OAR - 2004 - 0488 - 0041) . This report revealed that exposures over 4% (40,000 ppm) CO 2 are likely to cause discomfort and signs of intoxication that could impair the driver’s respon se to road and driving conditions , and could create safety and health ri sks to the passengers. In addition to this report, a revised risk anal ys is performed by the U.S. Army Research, Development and Engineering Command (herein referred as U.S. Army risk anal ys is ) 18 , submitted during the public comment period, indicated that limiting passenger exposure to 4% CO 2 is sufficientl y protective to avoid serious or irreversible health effects in potentially

sensitive subpopulations ( EPA - HQ - OAR - 2004 - 0488 - 0025 .2). Also, the U.S. Army risk anal ys is selected the 4% CO 2 level based on the lowest level at which performance decrements were observed in studies by Wong, 1992 ( EPA - HQ - OAR - 2004 - 0488 - 0025 .2) . Vehicle driver and passenger risks EPA’s review of vehicle driver and passenger risks from CO 2 refrigerant exposure indicated that a potential refrigerant leak into the vehicle passenger compartment is not expected to present an unreasonable exposure risk if engineering strategies or mitigation strategies are applied (EPA - HQ - OAR - 2004 - 0488 - 0025, - 0037.1). The U.S. Army risk assessment indicated a **17** SNAP rule listing as acceptable subject to use conditions HFO - 1234yf fo r MVACs in new passenger cars and light - duty vehicles ( 76 FR 17488, March 29, 2011). **18** Blackwell et. al 2006; Risk Analysis for Alternative Refrigerant in Motor Vehicle Air Conditioning (r evised risk analysis made in collaboration with EPA and several stakeholders, EPA - HQ - OAR - 2004 - 0488 - 0025.2) . The original risk screen referred in the NRPM (71 FR 55140) contained technical errors (EPA - HQ - OAR- 2004 - 0488 - 0017). This final rule relies on the results of the revised U.S. Army risk analysis.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 23 of 58 possible strategy

to limit refrigerant leakage into the passenger compartment by installing a device referred as a “3 - second squib valve” to discharge refrigerant to a location outside the passenger compartment three seconds after a major leak is detected. 19 The assessment showed that for CO 2 MVAC sy stems, using a squib valve to evacuate the charge in three seconds after a leak is detected kept passenger exposure to below levels of concern ( i.e., 3% over 15 minutes in the passenger compartment, as a whole, and 4% in the breathing zone ).We list ed in the proposal additional possible mitigation strategies that may reduce the likelihood of exceeding refrigerant levels of concern inside the passenger compartment , including within the breathing zone . We also received information from commenters on ad ditional engineering strategies and mitigation strategies (EPA - HQ - OAR - 2004 - 0488 - 0037.1, - 0025.2, - 0030, - 0050). In this final rule, we are not establishing a use condition requiring a specific mitigation strategy , but instead leav ing to vehicle manufacture rs the choice of which mitigation strategy to use in order to ensure that in the event of refrigerant leak, the resulting concentrations of CO 2 in the passenger free space above 3% or 30,000 ppm averag ed over 15 minutes are avoided and the resulting concentrations of CO 2 in the passenger breathing zone do not exceed the ceiling limit of 4% or 40,000 ppm at any time. Occupational risks EPA evaluated risks of injury and refrigerant exposure to workers by examining risk screens, published research information and data made available during the public comment period (EPA - HQ - OAR - 2004 - 0017, - 0025.2, - 0041, 0022, - 0015, - 0051). We compared long term occupational exposures to CO 2 to a workplace exposure limit of 5,000 ppm (or 0.5%) time weighted average CO 2 concentration over a period of eight hour s , consistent with the Occupational Safety and H ealth Administration (OSHA) Permissible Exposure Limit

–Time

19 Refers to the assessment by Blackwell, et. al, 2006 (EPA - HQ - OAR - 2004 - 0488 - 0025).*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 24 of 58 Weighted Average (PEL - TWA) 20 , the Centers for Disease Control and Prevention’s (CDC’s) National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit Time Weighted Average (REL - TWA) 21 , and the American Conference of Governmental Industrial Hygi enists (ACGIH) Threshold Limit Value - Time Weighted Average (TLV TWA). 22 , 23 Additionally, we compared short - term occupational worker exposures to CO 2 to a workplace short - term exposure limit of 30,000 ppm (or 3%) time weighted average CO 2 concentration over a 15 - minute period during a workday , consistent with NIOSH’s Recommended Exposure Limit - Short term Exposure Limit (REL - STEL) 24 and ACGIH’s Threshold Limit Value - Short Term Exposure Limit (TLV - STEL). 25 , 26 The U.S. Army risk assessment (EPA - HQ - OAR - 2004 - 0488 - 0025.2) evaluated occupational risks for the MVAC service sector using FTA. The FTA found probabilities of refrigerant exposure while servicing CO 2 MVAC sy stems of approximately 10 - 5 cases per ye ar (i.e., approximately

5 annual cases per 100,000 technicians ) (EPA - HQ - OAR - 2004 - 0488 - 0025) . This figure is significantly lower when compared to the general injury and illness rate for auto repair technicians, which is approximately 4 annual cases per 100 full time technicians (BLS, 2003; EPA - HQ - OAR - 2004 - 0488 - 0025 ); thus risk s from CO 2 exposures in the MVAC service field are expected to be significantl y less than the risks of injury already present in shops (EPA HQ - OAR - 2004 - 0488 - 0025). The U.S. Army risk assessment additionally found that the chances **20** PELs are based on an eight hour TWA exposure (OSHA, 1988a). **21** REL - TWAs are concentrations for up to 10 - hour workday during a 40 - hour workweek (N IOSH, 2005). **22** TLV - TWAs are concentrations for an eight hour workday and a 40 - hour workweek, to which is believed that nearly all workers may be repeatedly exposed, day after day, for a working lifetime without adverse effect (ACGIH, 2005). **23** OSHA’s PEL - TWA, NIOSH’s REL - TWA, and ACGIH’S TLV - TWA are all the same, 5,000 ppm (0.5%), for CO 2 (EPA - HQ - OAR- 2004 - 0488 - 0041). **24** REL - STELs are 15 - minute TWA exposure limits that should not be exceeded at any time during a workday (NIOSH, 2005). **25** TLV - STELs are 15 - minute exposure that should not b e exceeded at any time during a workday , even if the eight hour TWA is within the TLV - TWA (ACGIH, 2005). **26** N IOSH’s REL - STEL, and ACGIH’S TLV - STEL for CO 2 are all 30,000 ppm (3 %) 15 - minute TWA (EPA - HQ OAR - 2004 - 0488 - 0041).*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 25 of 58 of refrigerant exposure for persons servicing an MVAC sy stem do not vary considerabl y b y th e ty pe of refrigerant use d and found similar results for end - of - life (i.e., recycling or disposal) activities (EPA - HQ - OAR - 2004 - 0488 - 0025). EPA notes that occupational risks could occur during the manufacture of the refrigerant and initial installation of the refrigerant into the MVAC sy stem at the vehicle assembly plant . Although we did not analyze the risk of exposure during refrigerant manufacture and initial installation of CO 2 refrigerant into the MVAC s ys tem at the vehicle ass embly plant , we expect risks at the vehicle assembly plant, and at other workplaces were CO 2 refrigerant handling will occur (e.g., service shops, and recycling or disposal facilities ), to be similar to or lower than the risks from other refrigerants used for these purpose s due to occupational safety practices (e.g . , proper ventilation, use of personal protective equipment) established for these ty pe of facilities and subject to occupational safety and health standards under 29 CFR Part 1910 , which are intended to address risk to such workers . Overall conclusion EPA finds that the overall environmental and human health risks posed b y the use of CO 2 in new MVAC sy stems, subject to the use conditions being adopted in this final rule, is lower than or comparable to the risks posed by other substitutes found acceptable subject to use conditions in the same end - use. **VI. What is the relationship between this SNAP rule and other EPA rules?** 

Rules under Sections 609 and 608 of the Clean Air Act This final SNAP rule addresses the conditions for safe use of CO 2 in new MVAC sy stems. Thus, the requirements in this rule apply primarily to OEMs, except for specific requirements for unique fittings required under Appendix D to Subpart G of 40 CFR Part 8 2*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 26 of 58 which also applies for servicing of the MVAC . Section 609 of the CAA establishes standards and requirements regarding servicing of MVAC s ys tems. These requirements include training and certification of any person that services MVAC s ystems for consideration27 **,** as well as standards for certification of equipment for refrigerant recovery and recycling. EPA has issued regulations implementing th ese statutory requirement s and those regulations are codified at subpart B of 40 CFR part 82. MVAC end - of - life disposal and recycling specifications are covered under section 608 of the CAA and our regulations are codified at subpart F of 40 CFR part 82 . The s tatutory and regulatory provision s regarding MVAC servicing , refrigerant recovery , and ref rigerant venting prohibition appl y to any refrigerant alternative and are not limited to refrigerants that are also ODS. CO 2 is exempted fro m the refrigerant venting prohibition provisions promulgated under CAA 608 (40 CFR §82.154 and 70 FR 19278; April 13 , 2005). **VII. What is EPA’s response to public comments on the proposal?** 

This section summarizes EPA’s response to significant comments received during the public comment periods for the NPRM and the NODA. EPA’s response to all comments received can also be found in a response to comments document in docket EPA - HQ - OAR - 2004 - 0488. A. Use Conditions Comment: Some commenters claimed that the proposed STELof 3% CO 2 averaged ov er 15 minutes in the cabin free space is enough to protect passengers and ensure driver alertness . One commenter suggested to consider a 3% CO 2 concentration limit averaged over 15 minutes in the breath level (i.e., breathing zone) instead of 3% in the cabin free space. The commenter considered the breathing zone to be a relevant point for measurement and claimed that high

**27** Service for consideration means receiving something of worth or value to perform service, whether in money, credit, goods, or services (see 40 CFR §82.32 (g)) .*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 27 of 58 refrigerant concentrations lower in the vehicle would not impair vehicle operation. Other commenters supported higher CO 2 concentration limits but over a shorter period of time ( e.g ., 5.5 % CO 2 for 5 minutes and 9% CO 2 as a ceiling limit) . Other commenters requested that EPA include a CO 2 ceiling limit in the passenger breathing zone and one commenter considered appropriate a 4% CO 2 ceiling limit (i.e., a limit not to be exceeded at any time) as an additional use condition. Another commenter stated that use conditions requiring mitigation strategies are not necessary for low probability events (i.e., exceeding 4% CO 2 for any duration) and that requiring such conditions would prevent the use of this refrigerant. Response: After evaluating the comments and risk screens (EPA - HQ - OAR - 2004 - 0488 - 0025.2, - 0041, 0051), EPA is revising the proposed use conditions to add a ceiling limit of 4% CO 2 , in addition to the CO 2 STELof 3% averaged over 15 minutes . We believe that the original proposed use condition requiring mitigation strategies for MVAC s ys tems, to prevent leaks of CO 2 refrigerant reaching concentrations above 3% averaged over 15 minutes inside the passenger compartment free space, may not be sufficient on its own to protect drivers and passengers. We also believe that requiring a CO 2 ceiling limit of 4% is necessary because it is possible for a time - weighted average concentration, such as the STEL, to be under 3%, while peak concentrations could reach higher limi ts for a few minutes. As shown in published data , CO 2 concentration peaks above 4% could result in effects on hearing and vision that could distract and endanger a driver , or other , potentially more severe adverse health effects ( EPA - HQ OAR - 2004 - 0488 - 0041 ). CFD modeling showed that during unmitigated refrigerant leak scenarios , CO 2 refrigerant concentrations in the passenger breathing zone can reach up to 10.2% in 50 seconds (0.83 minutes) and 8.0% in 200 seconds (3.33 minutes) (EPA - HQ - OAR - 2004 - 0488 - 0025 .2) . The U.S.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 28 of 58 Army risk anal ys is ’s FTA showed that unmitigated leak scenario occurrences for CO 2 sy stems (reaching concentrations above 4% CO 2 ) could reach 4,300 per ye ar for the vehicle fleet (EPA HQ - OAR - 2004 - 0488 - 0025.2). Th ese occurrences are about 10,000 higher than the expected occurrences associated with leaks of a fluorinated refrigerant (e.g., HFC - 134a, HFC - 152a, or HFO - 1234yf) breakdown product (i.e., hydrogen fluoride) exposure above health based limits . 28 Several studies reported that exposure ranging from 7% to 10% CO 2 for few minutes (e.g., 2 - 3 minutes) resulted in loss of consciousness (EPA - HQ - OAR - 2004 - 0488 - 0441). 29 EPA disagrees with the commenter stating that use conditions requiring mitigation strategies are not necessary for low probability events and that requiring such conditions would prevent the use of this refrigerant. Consistent with the information above, w e believe that unmitigated exposure occurrences are not rare. We believe the use conditions required in this final rule are necessary to ensure that overall risks to human health and the environment from CO 2 will be similar to or less than those of other available refrigerants that EPA has already listed as acceptable for MVAC. We also believe th at requiring the use conditions listed in this final rule would not make the refrigerant use less practicable. Use conditions imposed on other acceptable alternatives for MVACs (e.g., adherence to all safety requirements under SAE standard J639, use of unique fittings and labels, use of pressure relief devices) has not prevented use of such alternatives. 30

28 T he risk due to exposure to HF when using HFO - 1234yf is approximately the same as that with the current use of HFC - 134a (on order of 10 - 12 occurrences per operating hour, or one in one trillion). (76 FR 17488; March 29, 2011). When this factor is multiplied by the approximate vehicle fleet and annual vehicle operating hours (250 million and 500hr/yr, respectively) the occurrences per year are in the order of 10 - 1

. 29 Unconsciousness caused by short term exposure (e.g., 2 - 3 minutes) of CO 2 concentration ranging from 7 to 10% wa s reported in studies by Aero Medical Association (1953), Flury and Zernik (1931), Hunter (1975), Schaefer (1951), and NIOSH (1996 ), as cited in Review of Health Impacts for Short- Term Carbon Dioxide Inhalation Exposures (2009). EPA - HQ - OAR - 2004 - 0488 - 0041. **30** On March 29, 2011, EPA issued a final rule listing HFO - 1234yf as a cceptable subject to use conditions for MVACs in new passenger car and light duty trucks. One of the use conditions in that rule require OEMs to perform and keep on file an FMEA. In an FMEA vehicle designers analyze all the ways in which parts of the MVAC system could fail and identify how they will address those risks in design of the system. (76 FR 17488). If the FMEA*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 29 of 58 Comment: Several commenters indicated that concentration measurements of CO 2 inside the passenger compartment should consider passenger respiration in addition to a refrigerant leak from the A/C sy stem. Another commenter indicated that the MVAC recirculation mode operates with at least 1% of fresh air. One commenter suggested chan ging the text of the proposed use condition indicating the STEL for CO 2 refrigerant inside the passenger compartment to state that the STELis “3% v/v fully- occupied - volume, time averaged over 15 minutes” and to clarify that the calculation of such value i s based on a double average consisting of the average CO 2 concentration over the air volume of a full y occupied car and a time - average of volume - average over 15 minutes. 31 Another commenter suggested alternative language for the use condition specifying a ceiling limit of 4% CO 2 applicable in any part of the free space inside the passenger compartment for a time period of 60 se conds when the car ignition is on . The suggested language reads: “Engineering strategies and/or devices shall be incorporated into the s ys tem such that foreseeable leaks into the passenger compartment do not result in R744 concentrations of 4.0% v/v or above in any part of the free space inside the passenger compartment for more than 60 seconds when the car ignition is on . ” Response: EPA notes that the U.S. Army risk analy sis assumed that a maximum number of passengers were in the vehicle before the release of refrigerant into the passenger compartment, allowing for some build - up of respiratory CO 2 (EPA - HQ - OAR - 2004 - 0488 - 0025.2). Thus, that anal ysis recognized that CO 2 concentrations can occur from human respiration in a space with limited exchange of outside air and may consequently

build up in the reports that mitigation strategies are necessary in the MVAC for safety reasons, manufacturers are required to design safety components (e. g., mitigation strategies) to comply with the use condition of that rule. In the U.S. an OEM publicly announced that it will be using HFO - 1234yf in some vehicles starting 2013 model year (EPA - HQ - OAR 2004 - 0488 - 0062). 31 Fully occupied is defined as the maxi mum design occupancy de termin ed by the number of sets of seat belts (EPA HQ - OAR - 2004 - 0488 - 0025.1

– 0025.2).*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 30 of 58 passenger cabin. For that reason, in the proposal, we indicated that OEMs should account for background CO 2 concentrations in the passenger compartment that can result from human respiration when designing their s ys tems and mitigation devices (71 FR 55140; September 21, 2006 ). However, we did not specify whether the vehicle should be full y occupied to account for CO 2 background concentrations. We believe that CO 2 refrigerant concentrations may reach levels of concern (i.e., above 4% CO 2 ) during an unmitigated event of refrigerant leak either when the vehicle is fully

occupied or when not fully occupied (e.g., the vehicle is occupied b y the driver onl y). Thus we do not agree with the commenter’s suggestion to state that the STEL is “3% v/v fully- occupied - volume, time averaged over 15 minutes”. In this final rule, we recommend but do not require , consistent with the NPRM, to account for background CO 2 concentrations from human respiration, in addition to refrigerant leaks when designing the MVAC. EPA notes that the proposal (79 FR 55140; September 21, 2006) specifies the CO 2 STEL as a concentration limit averaged over 15 minutes, in the event of a refrigerant leak. The STEL is determined from the sum of concentration and exposure time products (e.g., concentration 1 times exposure time 1 plus concentration 2 times exposure time 2) , divided by the to tal exposure time which shall not exceed 15 minutes (EPA - HQ - OAR - 2004 - 0448 - 0041). Thus the STELis a time - weighted average concentration and not necessarily a time - average of a volume - average as indicated b y the commenter since STEL refers to a total exposure time (i.e . , 15 minutes) and not an average time . For this reason, we do not agree with the commenter’s suggestion to clarify that the calculation of the 3% STEL is based on a double average consisting of the average CO 2 concentration over the air volume of a full y occupied car and a time - average of volume - average over 15 minutes since the approach does not provide further clarity of the use condition. Inthis*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 31 of 58 final rule, the CO 2 STELof 3% averaged over 15 minutes consid ers the average CO 2 concentration in a passenger cabin o ver a total time period of 15 minutes during the event of refrigerant leak; and the ceiling limit of 4% CO 2 considers the total CO 2 in the passenger breathing zone at any one moment in a passenger compartment during the event of a leak. Regarding the alternative language suggested b y the other commenter specifying a ceiling limit of 4% CO 2 applicable in any part of the free space inside the passenger compartment for a time period of 60 se conds when the car ignition is on, we note that the commenter did not provided information supporting his suggestion that the ceiling limit apply in areas other than the passenger breathing zone for the specified 60 second time period . Comment: Two commenters indicated the nee d for clarity on whether the use conditions apply when the ignition is o ff as well as when the ignition is o n . Other commenters suggested considering the results of a risk assessment performed by SAE’s CRP indicating a significantly low probability

for a leak when the ignition is off, and several other commenters stated that the use conditions should only appl y when the ignition is on. Response: The NODA provided data and requested additional comment on whether the use conditions should apply when the engine is off. In December , 2009 , after the public comment period closed on the NODA, SAE issued a report, “ Risk Assessment for HFO - 1234yf and R - 744 (CO 2 ) Phase III” (referred herein after as SAE CRP report), that evaluated toxicity effects and quantitative risks of CO 2 , similarly to the U.S. Army

risk analy sis . This report was submitted to EPA during the public comment period for another SNAP rulemaking . 32 The report evaluates CO 2 exposure estimations due to le aks into the passenger compartment during different modeled scenarios such as different MVAC operation mode, system failure, and during a collision (EPA -

**32** We refer here to the SNAP rule listing HFO - 1234yf as acceptable subject to use conditions for MVACs in new passenger cars and light duty vehicles (EPA - HQ - OAR - 2008 - 0644 , 74 FR 17488; March 29, 2011 )*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 32 of 58 HQ - OAR - 2008 - 0664 - 0056.2, EPA - HQ - OAR - 2004 - 0488 - 0025.2, - 0051). The SAE CRP report also evaluated refrigerant release into the passenger compartment during a scenario where the engine is expected to be off (EPA - HQ - OAR - 2004 - 0488 - 0051, EPA - HQ - OAR - 2008 - 0664 - 0056.2). For this scenario, which involves passengers sleeping inside a vehicle with the windows closed while refrigerant leaks occur, the SAE CRP report showed a probability for occurrences of CO 2 refrigerant exposure above 6 % ( a threshold limit used by the CRP for this scenario ) to be in the order of 10 - 1 2 per vehicle/hour/occupant (EPA - HQ - OAR - 2004 - 0488 - 0051, EPA - HQ OAR - 2008 - 0664 - 0056.2). We believe that exposures of concern inside the passenger compartment are more likely to result from a large, sudden release of refrigerant inside the passenger compartment and that such a situation is most likely during a collision while the ignition is on, as described on the U.S. Army risk anal ys is ( EPA - HQ - OAR - 2 004 - 0488 - 00 2 5 .2) and consistent with the SAE CRP report (EPA - HQ - OAR - 2004 - 0488 - 0051, EPA - HQ - OAR 2008 - 0664 - 0056.2). In addition, even if a rupture on the evaporator line is large, the overall leak rate is limited to the maximum flow rate of refrigerant through the fixed orifice tube opening of the MVAC ( EPA - HQ - OAR - 2 004 - 0488 - 00 2 5 .2). The maximum flow rate is determine d by the differential compressor discharge pressure, which is only available when the vehicle ignition is on and MVAC sy stem is running. Therefore, EPA finds that the overall risks to human health and the environment from CO 2 will be similar to or less than those of other available refrigerants that EPA has already listed as acceptable for MVAC when the ignition is off. Thus, consistent with a SNAP rule issued in June 12, 2008 (73 FR 33304) listing HFC - 152a 33 as acceptable subject to use conditions for use in new MVAC systems, the use conditions in this final rule apply onl y when the ignition is on.

**33** HFC - 152a poses risks comparable to CO 2 and other available refrigerants found acceptable subject to use conditions under SNAP (73 FR 33304; June 12, 2008).*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 33 of 58 Comment: One commenter suggested that the regulation should precisely define the area in the vehicle being regulated and indicated that SAE is working on a standard to establish standards for passenger compartment refrigerant concentration measurement. Another comm enter indicated that a CO 2 concentration limit should focus on the driver breathing zone rather than the cabin free space. Response: EPA has clarified the regulatory text of the use condition to define the passenger free space as the space inside the pas senger compartment , excluding the space enclosed b y the ducting in the HVAC module . The passenger breathing zone, where the ceiling limit of 4% must be met , is defined as the area inside the passenger compartment where the driver’s and passengers’ heads are located during normal sitting position (i.e., space where people breathe, as defined in the NODA ( 71 FR 47775; September 17, 2009 ) ). Additionally , we not e that the passenger breathing zone is defined in SAE J2772 and the driver’s head position in SAE J 1052. Since the automotive industry often relies on standards for designs and assessments, we recommend the use of the SAE J1052 and SAE J2772 standards as references for further specifications regarding the driver’s and passengers’ head and seating position and to establish the passenger breathing zone consistent with our explanation provided in Section V of the preamble ( i.e. , the area inside the passenger c ompartment where the driver’s and passengers’ heads are located during a normal sitting position) . EPA dis agrees with the comment indicating that a CO 2 concentration limit should only focus on the driver breathing zone rather than the passenger cabin free space . B ased on the risk anal ys es and available data , we include in this final rule a 4% ceiling limit that must not be surpassed at any time in the passenger (and driver) breathing zone (EPA - HQ - OAR - 2004 - 0488 - 0044 - 0025.2). We also include , as proposed , a 3% CO 2 STELaveraged over 15 minutes in the*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 34 of 58 passenger cabin free space as an additional protective measure for passenger exposure to CO 2 . As indicated b y the U.S. Army risk assessment, sensitive subpopulations (e.g., elderl y and children) may

be affected from exposures to high concentrations of CO 2 (EPA - HQ - OAR - 2004 - 0488 - 0025.2) , thus we believe it is necessary to set a limit that would address risk to all people in the passenger compartment and not solely the driver . We also take into consideration that passengers may

not be in a normal sitting position all the time (e.g., passenger may rest in a reclined position) and note CO 2 is heavier than air, thus higher concentrations may be found at lower points of the passenger cabin (EPA - HQ - OAR - 2004 - 0488 - 0025.2, - 0041, - 0051) . As indicated previousl y, the STELis the concentration limit that people can be exposed continuously

for a short period of time (i.e., 15 minutes) without suffering advers e health risks. For these reasons we include both limits (i.e., 4% CO 2 ceiling limit in the passenger breathing zone and 3% CO 2 averaged over 15 minutes in the passenger cabin free space) in this final rule. Comment: Several commenters suggested that a CO 2 ceiling limit shoul d rely on exposure time since potential effects of CO 2 vary with both concentration and duration of the exposure. One commenter stated that if the ceiling limit is exceeded, it is likely due to collision events. Response: EPA agrees the health effects of CO 2 are functions of exposures over time . The commenter appears to misunderstand what a ceiling limit is. A ceiling limit is a limit that shall not be exceeded for any period of time , thus it is not consistent with the concept of a ceil ing limit to also include a period of time during which it cannot be exceeded. As explained previously , we believe that both a ceiling limit and a STELare necessary to ensure that risks posed from CO 2 MVAC sy stems are not greater than risks posed by other available MVAC sy stems.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 35 of 58 While EPA agrees with the commenter that collision events are the most likely cause of a refrigerant leak that could cause CO 2 levels to the exceed the ceiling limit established in the use condition s , there may be other s ys tem failures that could cause the ceiling limit to be exceeded. OEMs should consider risks from all possible events in designing MVACs for use with CO 2 . Comment: Several commenters suggested considering ceiling limits of CO 2 above 4% (e.g., 6%, 9%) based on s tudies showing that visual disturbances occur at concentrations of 6% CO 2 . They

stated that the SAE CRP report’s rationale suggest ed a 9% CO 2 concentration ceiling limit , based on studies showing central nervous s ystem ( CNS ) effects at CO 2 exposure concentrations of 10% (100,000 ppm) . Response: Studies report that human exposures to 6% CO 2 for periods as short as 2 minutes can lead to hearing and visual disturbances, and that exposures to 7.5% for 5 minutes lead to significant reasoning and performance decrements (Gellhorn, 1936; Sayers, 1987 as cited in EPA - HQ - OAR - 2004 - 0488 - 0041). T o provi de a margin of safety, EPA considers it necessary to require a ceiling limit of 4% CO 2 in the passenger breathing zone as indicated in the NODA and suggested b y some commenters , to avoid driver performance decrement and other adverse health effects on pass engers. Comment : Several commenters said that the ceiling limit should rely on NIOSH’s Immediately

Dangerous to Life and Health ( ID LH ) value of 4% CO 2 based on a 30 - minute exposure. B. Response: EPA disagrees with the commenter s to the extent they are suggesting that the 4% limit be based on a 30 minute exposure. The NI OSH IDLH value is a worker’s exposure limit based on the effects that might occur as a consequence of a*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 36 of 58 30 - minute exposure (NIOSH 2005; EPA - HQ - OAR - 2004 - 0488 - 0041). The OSHA regulation (1910.134(b)) defines the term as "an atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability

to escape from a dangerous atmosphere." W e believe NIOSH’ s ID LH is inappropriate as a ceiling limit for the use of CO 2 as a ref rigerant in MVACs because, as indicated above, a ceiling limit is a limit that shall not be exceeded for any period of time. Also, a 4% limit over 30 minutes would not protect drivers and passengers from the effects of CO 2 exposure at concentrations equal or higher than 4% . CO 2 is an asphy

xiant that obstructs the oxygen flow into the body and we believe that 30 minute duration, in particular, where the person affected b y such a concentr ation may

be operating a vehicle and thus posing risk to others, creates a significant risk . Risk Mitigation Strategies Comment: The U.S. Army no ted a CFD parameter error in their 2005 risk analy sis which used an incorrect refrigerant leak angle in their 2005 risk anal ys is (EPA - HQ - OAR - 2004 - 0488 - 0017) . The U.S. Army corrected this error for purposes of their 2006 risk analy sis by using a perpendicular leak angle to the rupture cross - sectional area (EPA - HQ - OAR - 2004 - 0488 - 0025.1) . The 2006 anal ys is finds that an unmitigated discharge of CO 2 , in full recirculation mode, results in CO 2 concentration above 3% for more than 60 minutes. The U.S. Army also indicate d that a 3 - second, rather than a 10 - second squib valve, as originall y determined, would be needed to en sure that CO 2 concentrations remain below the 3% on a 15 - minute average inside the passenger compartment . Response: EPA notes that the U.S. Army is commenting on its own risk assessment performed in collaboration with EPA and several stakeholders, and referenced in the NPRM (71*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 37 of 58 FR 55140) . We also note that the 2005 U.S. Army risk anal ys is referred in the NRPM (71 FR 55140) contained technical errors (EPA - HQ - OAR - 2004 - 0488 - 0017). This final rule relies on the results of the revised (2006) U.S. Army risk anal ysis submitted during the public comment period. Based on the U.S. Army revised assessment, we understand that, in order for a squib valve to be an effective mitigation device, the activation time of such device should be 3 seconds rather than the 10 seconds indicated in the original risk assessment. Since we are not specifying in this final rule what mitigation strategies must be used , we believe the 2006 revised risk anal ys is does not affect the use conditions addressed in this final rule, but may affect the potential risk mitigation strategies OEMs might apply for use with CO 2 refrigerant. Comment: One comment er stated that secondary loop technology is not a viable risk mitigation strategy

f or CO 2 because of reduced s ystem performance and reduced fuel efficiency. Response: This final rule does not specify design options. EPA does not intend to limit engineering innovation by requiring any

specific risk mitigation strategy ; however, EPA notes that secondary

loop technology

could potentiall y reduce the risks of exceeding the ceiling limit of CO 2 in the passenger compartment bec ause the refrigerant charge stays separate from the pa ssenger compartment. OEMs may choose to investigate secondary loops as a risk mitigation strategy , and would have to weigh the pros and cons, including any potential effect on fuel efficiency . H owever, even if secondary loop technology

were not an attractive option, other feasible mitigation technologies could be applied to meet the use conditions of this final rule, such as a squib valve with a 3 - second response time. Comment: One commenter indicated th at squib valves with activation time of less than 10 seconds (e.g., few milliseconds) are available and such devices have been tested. Another*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 38 of 58 commenter stated that a 10 - second squib valve is not technicall y feasible given CO 2 sensor performance . Additionally , the commenter stated that during sharp increases in CO 2 concentration in the passenger compartment , a short activation time for a squib - valve would increase the possibility

of purging the refrigerant from the air conditioning sy stem to outsid e the vehicle when no leak in fact exists . Response : EPA agrees with the first commenter regarding the availability of squib valves and disagrees with the second commenter’s statement regarding feasibility of a squib valve. The 2006 U.S. Army

risk analy sis indicated that a squib valve is one effective strategy and viable engineering option to reduce the amount of charge that could potentially leak into the passenger compartment (EPA - HQ - OAR - 2004 - 0488 - 0025.2). EPA notes that in the proposal, we intended for the squib valve activation time to include : 1) the time the sensor takes to detect a significant leak that would cause CO 2 refrigerant to enter into the passenger compartment , and 2) the time it takes for the squib valve to open ( 71 FR 55140; September 21, 2006) . The 2006 U.S. Army risk assessment evaluated different activation time s (i.e., 30, 10 and 3 seconds) of squib valve during modeled scenarios of CO 2 refrigerant leak. The results showed higher effectiveness of the valve preventing high refrigerant concentration reaching the passenger compartment during the shorter activation time. EPA believes that sharp increases in CO 2 concentration in the passenger compartment will likely

occur onl y when a significant amount of CO 2 refrigerant leaks into the passenger compartment. Risk assessments showed that CO 2 buildup due to passenger respiration occurs slowly (e.g., 60 minutes) to levels up to 2.4% in a fully- occupied 100 cubic feet sealed passenger compartment of a vehicle with no introduction of outside air (EPA - HQ - OAR - 2004 - 0488 - 0025.2,

- 0041) . EPA notes that a passenger compartment in a vehicle is not confined space and*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 39 of 58 infiltration/exfiltration rates of air changes within the passenger compartment and outside air are at least 0.3 air changes per hour (NREL , 2003 as cited in EPA - HQ - OAR - 2004 - 0488 - 0025.2). Therefore, we do not agree that refrigerant purging from the air conditioning s ys tem to outside the vehicle will occur when no leak in fact exists . Comment: A commenter stated that odorants that alert drivers to a leak should be another option for compliance with the rule. Response: EPA did not propose the use of odorants, and this final action neither requires nor prohibits the use of odorants in new CO 2 MVAC sy stems. Odorize d CO 2 may be an effective means to alert the driver and passengers to a refrigerant leak into the passenger compartment. However, EPA does not believe odorants used alone provide sufficient risk mitigation as it may take vehicle occupants a period of time to recognize what the odor signifies . Documentation has not been provided to show how long and how much odorized CO 2 drivers must be exposed to before they recognize that the smell indicates a health and safety risk . Comment: One commenter suggested that EPA consider use of sensors to allow continuous monitoring of refrigerant concentration inside the passenger cabin as a mitigation strategy . Ano ther commenter mentioned that an alarm system or other technical solutions should allow for air renewal and lowering concentration levels below the limits indicated in the use conditions within a reasonable time period Response: As noted previously , EPA is not specifyingthe risk mitigation strategies that must be used to ensure CO 2 levels do not exceed the levels established in the use conditions. W e do not believe that a sensor alone would be sufficient to provide effective protection to the passengers and to ensure that concentrations inside the passenger compartment and passenger breathing zone do not exce ed the established CO 2 concentration limits of this final rule. In*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 40 of 58 response to the commenter stating that an alarm system or other technical solutions should allow for air renewal, EPA believes the use of such tool might be effective but that such strategy would need to rel y on an automatic supply of air, rather than a driver’s response, to ensure CO 2 concentrations do not exceed the exposure limits established in the use conditions . Thus, an additional mitigation device would need to be used in addition to any alarm sy stem. Comment: One commenter said that evaporator isolation valves are not realistic as mitigation devices because of cost . The commenter stated that close - coupled and hermeticall y sealed s ys tems are technically feasible and note d that an automatic increase in air exchange is a possible strategy that is technicall y feasible. Ano ther commenter suggested that switching the MVAC blower to operate on outside air mode on high, rapidl y after CO 2 refrigerant is released, could reduc e the overall refrigerant concentration in the compartment to a peak lower than 4 %. Response: EPA believes the mitigation strategies mentioned by the commenters may all be technically

feasible means to meet concentration levels specified in the use conditions . We note that in the proposed rule we suggested using evaporator isolation valves, close coupled or hermeticall y closed s ys tems that would reduce refrigerant charge size, and increasing air exchange (with outside air) in the passenger compartment upon detection of leaks as some of several potential risk mitigation strategies (71 FR 55140; September 21, 2006). In this final rule we are not requiring a specific mitigation strategy or engineering device. We are allowing OEMs to choose a mitigation strategy that is consistent with the use conditions and that they will employ to protect the driver and passengers in a vehicle from CO 2 exposure above the limits specified in this rule. Comment: One commenter stated that a vehicle crash could be so severe that the MVAC sy stem evaporator could be damaged and possibly reduce a risk mitigation system’s*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 41 of 58 effectiveness. The commenter proposed the inclusion of an evaporator crush resistance standard in this action . Response: EPA agrees that a vehicle crash could reduce the effectiveness of the risk mitigation strategy . However we believe that in such a case, the damage to the car would be so severe as to result in an inflow of ambient air that would negat e the risk s associated with potentially

elevated CO 2 concentrations. A crush - resistant evaporator could be selected as a possible mitigation strategy but, as stated previously , in this final rule we do not specify which engineering device or strategies must be incorporated into the MVAC system and leave this choice to the OEMs. C . In dustry

Standards Comment: Several c ommenters indicated that SAE is developing standards for safety and servicing of CO 2 MVAC sy stems and that it is customary for OEMs to follow those standards . Other commenter claimed that every OEM is responsible for its own safety concept and has to show compliance with already existing and future safety standards. Response: EPA notes and agrees with the important role industry standards play particularl y for the MVAC sector. In addition, we note that the regulatory text reference s the relevant SAE technical standards to promote consistency with established industry practices. Specifically , use conditions in this final rul e reference SAE J639 (2011 version). Other standards such as SAE J1739, which addresses design, safety, and recordkeeping requirements, are recommended to help ensure that the use conditions are met. We disagree with the comment stating that every OEM is responsible for its own safety concept because we believe that in addition to customary business standards and industry practices outside the scope of this rule, OEMs will comply with all the use conditio ns specified*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 42 of 58 in this rule. Comment: Commenters noted that SAE is developing SAE J 2 77 2 standard, “Measurement of Passenger Compartment Refrigerant Concentrations under s ys tem refrigerant leakage conditions” (EPA - HQ - OAR - 2004 - 0448 - 0054) and SAE J 2 773 standard , “Standard for Safety and Risk Anal ys is for Use in Mobile Air Conditioning Sy stems” (EPA - HQ - OAR - 2004 - 0448 - 00553), formerl y known as Refrigerant Guidelines for Safety and Risk Analysis for Use in Mobile Air Conditioning Sy stems. Response: We note that standards J2772 and J2773 were recently published and are readil y available. In the comments column of our listing decision, we recommend the use of J 2772 and J 2 773 standards as well as other available standards such as SAE J1052, Motor V ehicl e Driver and Passenger Head Position (EPA - HQ - OAR - 2004 - 0448 - 0055) . D . Servicing Comment: One commenter indicated CAA Section 609 - certified, independent MVAC service technicians should be consulted before the rule is issued. Response: EPA took comments on a range of topics during the 60 - day public comment period. In addition, EPA contacted the National Institute for Automotive Service Excellence (ASE), which represents a significant number of MVAC service technicians . A summary is in the docket for this final rule. ASE stated they did not see any servicing concerns in the proposal that would impact the service technicians they represent , but would be interested in any follow on rulemaking that will address MVAC servicing for consideration under CAA Secti on 609 and codified at 40 CFR Part 82 Subpart B (EPA - HQ - OAR - 2004 - 0488 - 0031) . Comment: One commenter said risks associated with MVAC service should be considered. Response : EPA agrees with the commenter and notes that risk associated with service*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 43 of 58 were evaluated in the published risk analyses (EPA - HQ - OAR - 2004 - 0488 - 0017, - 0025.2, - 0041, - 0051) and discussed in the preamble to the proposed rulemaking (71 FR 5514 4 September 21, 2006) . Additional details regarding our evaluation of risk associated with MVAC service can be found in Section V I of th is final rule preamble (Why is EPA listing CO 2 acceptable subject to use conditions?). As explained in more detail in Section VI above , we do not believe it is necessary to establish any

use conditions regarding serv icing because the overall environmental and human health risks posed by the use of CO 2 in new MVAC s ys tems, subject to the use conditions being adopted in this final rule, is lower than or comparable to the risks posed b y other substitutes found acceptabl e subject to use conditions in the same end - use. Comment: One commenter requested more information on why CO 2 systems are not found acceptable as a substitute in retrofitted sy stems. Response: In the original SNAP rulemaking (59 FR 13854; March 18, 1994), EPA listed CO 2 as an acceptable substitute for CFC - 12 only for new MVAC s ys tems. We have never receive d a SNAP submission requesting consideration of CO 2 in retrofitted MVAC sy stems . EPA understands that the higher working pressure of CO 2 compared to CFC - 12 and other SNAP acceptable refrigerants could raise significant issues with retrofitting such sy stems to CO 2 . Because we have not received a request to use CO 2 in retrofitted sy stems, which would include the technical and other analyses necessary to determine whether such use would present more risk than other available substitutes, this final rule only applies to the use of CO 2 as a refrigerant in new MVAC sy st ems , consistent with the NPRM (71 FR 55140; September 21, 2006) . When and if the Agency

receives a submission for retrofitting to CO 2, we will consider CO 2 for use as a refrigerant to retrofit existing MVAC s ys tems.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 44 of 58 **VIII. Statutory and Executive Order Reviews** 

A . Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review Under Executive Order (EO) 12866, (58 FR 51735; October 4, 1993) this action is a “significant regulatory

action.” It raises novel legal or policy issues arising out of legal mandates, the President’s priorities, or the principles set forth in the Executive Order. Accordingl y, EPA submitted this action to the Office of Management and Budget (OMB) for review under Executive Orders 12866 and 13563 (76 FR 3821, January 21, 2011) and any

changes made in response to OMB recommendations have been documented in the docket for this action. B. Paperwork Reduction Act This action does not impose any new information collection burden under the Paperwork Reduction Act ( 44 U.S.C. 3501 et seq) . This action is an Agency determination. Itcontains no new requirements for reporting. The onl y new recordkeeping requirement involves customary business practice. This rule requires minimal recordkeeping of studies done for three ye ars to ensure that MVAC s ys tems using CO 2 meet the requirements set forth in this rule. Because it is customary

business practice that OEMs conduct and keep on file records of the tests they perform , consistent with a widel y recognized industry standard, SAE J1739 ( Potential Failure M ode and Effect Analy sis in Design [ Design FMEA ], Potential Failure Mode and Effect Analy sis in Manufacturing and Assembly Processes [Process FMEA]), on any potentiall y hazardous part or s ys tem from the beginning of production of a vehicle model until three years or more after production of the model ends , we believe this requirement will not impose an additional paperwork burden. However, the Office of Management and Budget (OMB) has previously

approved the information collection requirements contained in the existing*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 45 of 58 regulations in subpart G of 40 CFR part 82 under the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq . and has assigned OMB control numbers 2060 - 0226 . The OMB control numbers for EPA's regulations are listed in 40 CFR Part 9. C. Regulatory

Flexibility

Act The Re gulatory

Flexibility

Act (RFA) generall y requires an agency to prepare a regulatory

flexibility

analy sis of any

rule subject to notice and comment rulemaking requirements under the Administrative Procedure Act or any other statute unless the agency certifies that the rule will not have a significant economic impact on a substantial number of small entities. Small entities include small businesses, small organizations, and small governmental jurisdictions. For purposes of assessing the impacts of today's rule on small entities, small entity is defined as: (1) a small business , as defined b y the Small Business Administration’s (SBA) regulations at 13 CFR 121.201;” (2) a small governmental jurisdiction that is a government of a city , county, town, school district or special district with a population of less than 50,000; and (3) a small organization that is any not - for- profit ent erprise which is independently owned and operated and is not dominant in its field. After considering the economic impacts of this final rule on small entities, I certify that this action will not have a significant adverse economic impact on a substantial number of small entities. This final rule modifies the current listing of CO 2 as an acceptable alternative refrigerant subject to use conditions necessary for the safe use of CO 2 in MVAC in new motor vehicles. The use conditions will need to be met by large entities (i.e., OEMs) that manufacturer motor vehicles if these choose to use CO 2 as a refrigerant in new MVACs. This final rule does n ot mandate the use of CO 2 as a refrigerant in new MVAC sy stems, thus will not impose significant*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 46 of 58 requirements on s mall entities such as MVAC service shops . This final rule effectivel y ensures c onsistency

with current practices in MVAC service shops regarding the use of unique fittings. It is not clear that there would be any cost differential between the unique fittings required for the use of CO 2 and those used with the current automotive refrigerant, HFC - 134a, or other fittings that the industry

could adopt instead , for other refrigerants . It is possible that the fittings required in the revised use co ndition will be equally or less expensive than those required for other acceptable alternative refrigerants because they are a standard shape and size and can be easily pro duced in a metal - working shop. Thus, cost impacts of this final rule on small entiti es are expected to be small. Although this final rule will not have a significant economic impact on a substantial number of small entities, EPA nonetheless has tried to reduce the impact of this rule on small entities. EPA has worked together with SAE International and with groups representing professional service technicians such as the Mobile Air Conditioning Society Worldwide, which conducts regular outreach with technicians and owners of small businesses such as retail refrigerant suppliers and automobile repair shops. D. Unfunded Mandates Reform Act This action contains no Federal mandates under the provisions of Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), 2 U.S.C. 1531 - 1538 for State, local, or tribal governments or the private sector . This action does not affect State, local, or tribal governments. The enforceable requirements of this action related to integrating risk mitigation devices and documenting the safety of alternative MVAC systems affect only a small number of OEMs. The impact of this action on the private sector will be less than $100 million per year. Thus, this action is not subject to the requirements of sections 202 and 205 of the UMRA. This action is*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 47 of 58 also not subject to the requirements of section 203 of UMRA because it contains no regulatory requirements that might significantl y or uniquely affect small governments. This action applies directly to facilities that use these substances and not to governmental entities. E. Executive Order 13132: Federalism This action does not have federalism implications. It will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government, as specified in EO 1313 2 (64 FR 43 2 55, August 10, 1999) . This regulation applies directly to facilities that use these substances and not to governmental entities. Thus, E O 1313 2 does n ot apply to this rule. F. Executive O rder 13175: Consultation and Coordination with Indian Tribal Governments This final rule does not have tribal implications, as specified in EO 13175 (65 FR 67 2 49, November 6, 2 000) . It does not significantl y or uniquely affect the communities of Indian tribal governments, because this regulation applies directly to facilities that use these substances and not to governmental entities. Thus, EO 13175 does not apply to this rule. G. Executive O rder 13045: Protection of Chi ldren from Environmental Health Risks and Safety Risks This final rule is not subject to the EO 13045 ( 6 2 FR 19885, April 2 3, 1997) because it is not economicall y significant as defined in Executive Order 1 2 866, and because the Agency does not have reason to believe the environmental health or safety risks addressed by this action present a disproportionate risk to children. This action’s health and risk assessments are*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 48 of 58 discussed in sections V I and VIII of the preamble and in documents EPA - HQ - OAR - 2004 - 0488 - 0025.2 , EPA - HQ - OAR - 2004 - 0488 - 0041 and EPA - HQ - OAR - 2004 - 0488 - 0051 in the docket for this rulemaking . H. Executive O rder 13211: Actions that Significantly Affect Energy

Supply , Distribution, or Use This rule is not a “significant energy action” as defined in Executive Order 13 2 11 (66 FR 28355 ; May 22, 2001 ) because it is not likely to have a significant adverse effect on the suppl y, distribution, or use of energy . This action would impact manufacturers of CO 2 MVAC systems for new vehicles . Preliminary information indicates that these new s ys tems are equally or more energy efficient than currently

available s ys tems in some climates. Therefore, we conclude that this rule is not likely

to have any

adverse effects on energy suppl y, distribution or use. I. National Technology

Transfer Advancement Act Section 1 2 (d) of the National Technology Transfer and Advancement Act of 199 5, Public Law No. 104 - 113, Section 1 2 (d) (15 U.S.C. 2 7 2 note) directs EPA to use voluntary consensus standards in regulatory

activities unless to do so would be inconsistent with applicable law or otherwise impractical. Voluntary consensus standards are technical standards (e.g., materials specifications, test methods, sampling procedures, and business practices) that are developed or adopted b y voluntary consensus standards bodies. NTTAA directs EPA to provide Congress, through OMB, explanations when the Agency decides not to use available and applicable voluntary consensus standards. This rulemaking involves technical standards. EPA has decided to use, by reference , the 2011 version of SAE standard J639 which is a voluntary consensus standard. This standard can be obtained from http://www.sae.org/technical/st andards/ . This standard addresses safety and*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 49 of 58 reliability issues of CO 2 MVAC sy stems. J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low - Income Populations Executive Order 12898 (59 FR 7629 ; February 16, 1994) establishes federal executive po licy on environmental justice. It s main provision directs federal agencies, to the greatest extent practicable and permitted by law, to make environmental justice part of their mission by identifying and addressin g, as appropriate, disproportionately high and adverse human health or environmental effects of their programs, policies, and activities on minority populations and low income populations in the United States. EPA has determined that this final rule will not have disproportionatel y high and adverse human health or environmental effects on minority or low - income populations because it increases the level of environmental protection for all affected populations without having any disproportionately

high and adverse human health or environmental effects on any population, including any minority or low - income population. The refrigerant CO 2 is a non ozone - depleting substance with a GWP of 1.0 . Based on the toxicological and atmospheric data described earlier, the use of CO 2 subject to the use conditions specified in this final rule will not have any disproportionately

high and adverse human health or environmental effects on any population, including any minority or low - income population. This final rule require s specific use conditions for MVAC s ys tems, if motor vehicle manufacturers cho o se to market MVAC sy stems using this refrigerant alternative. K. Congressional Review Act The Congressional Review Act, 5 U.S.C. 801 et seq., as added b y the Small Business Regulatory

Enforcement Fairness Act of 1996, generall y provides that before a rule may take*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 50 of 58 effect, the agency

promulgating the rule must submit a rule report, which includes a cop y of the rule, to each House of Congress and to the Comptroller General of the United States. EPA will submit a report containing this rule and other required information to the U.S. Senate, the U.S. House of Representatives, and the Comptroller General of the United States prior to publication of the rule in the Federal Register. A Major rule cannot take effect until 60 days after it is published in the Federal Register. This action is not a “major rule” as defined by 5 U.S.C. 804( 2 ). This rule will be effective [ **insert date 6**  **0 days after publication in the Federal Register**  ] . **IX. Referen**  **ces**

The documents below are referenced in the preamble. All documents are located in the Air Docket at the address listed in section titled ``ADDRESSES'' at the beginning of this document. Unless specified otherwise, all documents are available in Docket ID No. EPA - HQ OAR - 2004 - 0488 at http://www.regulations.gov . ACGIH, 2005a. TLVs® and BEIs® Based on the Documentation of the Threshold Limit Values for Chemical Substances and Phy sical Agents & Biological Exposure Indices. American Conference of Governmental Industrial Hygienists (ACGIH), Cincinnati, Ohio. ACGIH, 2005b. Docum entation of the Threshold Limit Values for Chemical Substances: Carbon Dioxide. American Conference of Governmental Industrial Hygi enists (ACGIH), Cincinnati, Ohio. Aero Medical Association, 1953. Committee on Aviation Toxicology , Blakiston, New York. As cited in CDC IDLH documentation for carbon dioxide. Avail able online at: http://www.cdc.gov/niosh/idlh/124389.html . AIHA, 1964. Carbon dioxide, Hygi enic guide series. Am erican Ind ustrial Hyg iene Assoc iation J 25:519-521. Avail able online at: http://www.cdc.gov/niosh/idlh/124389.html . Al - Delaimy W.K., Hay S.M., G ain K.R., Jones D.T., Crane J., 2001 . The effects of carbon dioxide on exercise - induced asthma: an unlikel y explanation for the effects of Buteyko breathing training. Med J Aust. 15,174(2):64 - 5.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 51 of 58 ANSI/ASHRAE, 2007. ASHRAE Standard 62.1 - 2007: Ventilation for Acceptable Indoor Air Quality . American National Standard Institute, American Society for Heating, Refrigerating, and Air- Conditioning Engineers (ASHRAE), Atlanta, GA. ASHRAE, 2006. BSR/ASHRAE Addendum to ANSI/ASHRAE Standard 34 - 2004

– Designation and Safety Classification of Refrigerants, Publication Draft. American Society for Heating, Refrigerating, and Air- Conditioning Engineers (ASHRAE), Atlanta, GA. Atkinson, W., 2002. Consumer Use of A/C S ys tems. SAE Automotive Alternate Refrigerant Sy stems Sy

mposium 2002. Phoenix, Arizona. Amin, J., B . Dienhart, and J. Wertenbach., 1999. Safety Aspects of an A/C Sy stem with Carbon Dioxide as Refrigerant, SAE Subcommittee Safety of Refrigerant Sy stems. Birgfeld, E., 2003. Risk Analy sis for CO 2 , HFC - 152a, and Hydrocarbon Refrigerants in MACs, presented at The Earth Technologies Forum, Washington, DC, April 2003. Beck J.G., P.J. Ohtake, and J.C. Shipherd., 1999. Exaggerated anxiety is not unique to CO2 in panic disorder: A comparison of hy percapnic and hy

poxic challenges. J Abnorm Psychol 108:473 - 482. Blackwell, N., L. Bendixen, E. Birgfield., 2006. Risk Analy sis for A lternative Refrigerant in Motor Vehicle Air Conditioning. Brown. E.W., 1930. The value of high ox ygen in preventing the phys iological effects of noxious concentrations of carbon dioxide. U.S. Naval Med. Bull. 132 , 523 - 553. As cited in Wong 1992. Bureau of Labor Statistics (BLS) , 2003. “Workplace Injuries and Illnesses in 2002,” December 18, 2003. CATAM., 1953. Aviation Toxicology , An Introduction to the Subject and a Handbook of Data. Committee on Aviation Toxicology , Aero Medical Association. The Blakiston Co.: New York, NY. Pp. 6 - 9, 31 - 39, 52 - 55, 74 - 79, 110 - 115. As cited in Wong 1992. Compressed C yl inder Gas (CGA) Association, 1 999 . Properties, Manufacture, Uses, and Special Requirements for Safe Handling. Carbon Dioxide. Handbook of Compressed Gases, 4 th edition. Arlington, VA Klever Academy . Pages 300 - 308. CRP, 2009. Risk Assessment for Alternative Refrigerants HFO - 1234yf and R744 (CO 2 ) Phase II I. Prepared for SAE International Cooperative Research Program 1234 b y T. Lewandowski, Gradient Corporation. December 17, 2009. DOT, Federal Aviation Authority , 1996. Allowable carbon dioxi de concentration in transport category airplane cabins; final rule. Federal Register 61(232):63951 - 63956.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 52 of 58 Dripps, R.D., J.H. Comroe, Jr., 1947 . The respiratory and circulatory

response of normal man to inhalation of 7.6 and 10.4 percent CO 2 with a comparison of the maximal ventilation produced b y severe muscular exercise, inhalation of CO 2 and maximal voluntary hy perventilation. Am J Phy siol 149:43 - 51. As cited in NI OSH, 1976 and NRC, 1996. ERG Inc., 2009. Review of Health Impacts from Short Term Carbon Dioxide Inhalation Exposures. 110 Hartwell Ave. Lexington, MA 02421. February 18, 2009. Froehling, J., M. L orenz - Boernert, F. Schroeder, V. Khetarpal, S. Pitla. (2002) “Component Design for CO 2 ,” presented at 2002 SAE Automotiv e Alternate Refrigerant Systems Sy mposium, Scottsdale, Arizona. Gellhorn, E. ( 1936 ) . The Effect of O2 - Lack, Variations in the Carbon Dioxide - Content of the Inspired Air, and Hy

perpnea on Visual Intensity Discrimination. American Journal of Physiology . 115: 679

– 684. Hunter D. ( 1975 ) . The diseases of occupations . 5th ed. L ondon: Hodder and Stoughton, p. 618 Jetter, J., R. Forte, and F. Delafield. (2001) “Refrigerant Concentrations in Motor Vehicle Passenger Compartments,” ASHRAE Transactions: Research, No. 4466, pp. 99 - 107. Lambertsen, C.J. ( 1971 ) . Therapeutic Gases: Ox yg en, Carbon Dioxide, and Helium. In Drill’s Pharmacology in Medicine , ed. J.R. DiPalma, 1145

– 1179. New York, NY: McGraw - Hill. NI OSH , 1976. Criteria for Document for Carbon Dioxide. NI OSH Publication No. 76

– 194. NI OSH, 1990. Pocket Guide to Chemical Hazards. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institutes for Occupational Safety and Health (NIOSH), Washington, DC . Available online at: http://www.cdc.gov/niosh/npg/ NI OSH, 1996. Documentation for Immediatel y Dangerous to Life or Health Concentrations (IDLHs): Carbon dioxide. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institutes for Occupational Safety and Health (NIOSH), Washington, DC. Available online at: http://www.cdc.gov/niosh/idlh/124389.htm l NI OSH, 2005. Pocket Guide to Chemical Hazards. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institutes for Occupational Safety and Health (NIOSH), Washington, DC . Available online at : http://www.cdc.gov/niosh/npg/ NRC, 1996. Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants: Volume 2. Subcommittee on Spacecraft Maximum Allowable Concentrations, Committee on Toxicol ogy , Board on Environmental Studies and Toxicology , Commission on Life Sciences, National Research Council (NRC).*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 53 of 58 Washington, DC: National Academies Press . Available online at : http://darwin.nap.edu/books/0309054788/html/105.html NRC, 2007. Emergency

and Continuous Exposure Guidance Levels for Selected Submarine Contaminants. Subcommittee on Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants, Committee on Toxicology , Board on Environmental Studies and Toxicology , National Research Council (NRC). Washington, DC: National Academies Press. Available online at: http://www.nap.edu/catalog.php?record_id=11170#toc OSHA , 1989. Carbon Dioxide, Industrial Exposure and Control Technologies for OSHA Regulated Hazardous Substances, Volume I of II, Substance A

–I. Occupational Safety and Health Administration. Washington, DC: U .S. Department of Labor. March 1989. OSHA, 1993. Final R

ule on Air Contaminants: FR 58:35338 - 35351, June 30, 1993. U.S. Department of Labor, Occupational Safety an d Health Administration (OSHA), Washington, DC. Available online at : http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=FEDERAL _REGIS TER&p_id=13306 OSHA, 1996. Hazard Information Bulletin. Potential Carbon Dioxide (CO 2 ) Asphy xiation Hazard When Filling Stationary L ow Pressure CO 2 Supply Sy stems. Available online at: http://www.osha.gov/pls/oshaweb /owadisp.show_document?p_table=HIB_STATI C&p_i d=35791&p_search_ty

pe=CL OBTEXTPOLICY&p_search_str=carbon+dioxide&p_text_ version=FAL SE#ctx1 . OSHA, 1997. Regulations (Standards

– 29 CFR); Table Z - 1 Limits for Air Contaminants

– 1910.1000. U.S. Department of Labor, Occupational Safety and Health Administration (OSHA), Washington, DC. Available online at: http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table= STANDARDS&p_ id=9992 Patterson, J.L ., H. Hey

man, L .L . Battery , R.W. Ferguson., 1955. Threshold of response of the cerebral vessels of man to increases in blood carbon dioxide. Journal of Clinical Investigations . 34:1857

– 1864. Pine, D.S. et al., 2005. Response to 5% carbon dioxide in children and adolescents: relationship to panic disorder in parents and anxiety disorders in subjects. Arch Gen Psychiatry 62:73 - 80. Rebinger, C., 2005. Safety Concept Proposal for R744 A/C Systems in Passenger Cars

— Update 2005. VDA Alternate Refrigerant W inter Meeting 2005 . Saalfelden, Austria. RI SA Sicherheitsanal ys en ., 2002. Safety- Study for a Prototy

pical Mobile R744 A/C System. VDA Alternate Refrigerant W inter Meeting 2002 . Saalfelden, Austria*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 54 of 58 Schaefer K.E. , 1951. Studies of carbon dioxide toxicity . New London, CT: Navy Department, Bureau of Medicine and Surgery , Medical Research L aboratory , U.S. Naval Submarine Base, Vol. 10, Report No.181, pp. 156 - 189. As cited in NIOSH documentation for carbon dioxide. Last accessed January 23, 2009: http://www.cdc.gov/niosh/idlh/124389.html . Sayers, J.A., R.E.A. Smith, R.LHolland, W.R. Keatinge. 1987. Effects of Carbon Dioxide on Mental Performance. Journal of Applied Physiology . 63(1):25

–30. Schneider, E.C., E. Tru esdale. , 1922. The effects on circulation and respiration of an increase in the carbon dioxide content of blood in man. American Journal of Physiology . 63:155

– 175. Schulte, J.H., 1964. Sealed environments in relation to health and disease. Archives of Environmental Health . 8: 438

–452. SAE International, 2002. Surface Vehicle Standard J1052. Motor Vehicle Driver and Passenger Head Position. SAE International, 2005. Surface Vehicle Standard J2683. Refrigerant Purity and Containment Requirements for Carbon Dioxide ( CO2 R - 744 ) Used in Mobile Air- Conditioning Sy stems. SAE International, 2009. Surface Vehicle Standard J1739. Potential Failure Mode and Effect Analy sis in Design (Design FMEA), Potential Failure Mode and Effect Analy sis in Manufacturing and Assembly Processes (Process FMEA). SAE International , 2011 . Surface Vehicle Standard J639. Safety Standards for Motor Vehicle Refrigerant Vapor Compression Sy stems. SAE International, 20 11. Surface Vehicle Standard J2772. Measurement of Passenger Compartment Refrigerant Concentrations Under System Refrigerant Leakage Conditions. SAE International, 2011. Surface Vehicle Standard J2773. Standard for Refrigerant Risk Analy sis for Mobile Air Conditioning Systems. Sumantran, V., B. Khali ghi, K. Saka, and S. Fischer., 1999. An Assessment of Alternative Refrigerants for Automotive Applications based on Environmental Impact. General Motors R&D Center and Oak Ridge National Laboratory . US EPA ., 1994. SNAP Technical B ackground Document: Risk Screen on the Use of Substitutes for Class I Ozone - Depleting Substances: Refrigeration and Air Conditioning. Stratospheric Protection Division. March 1994. US EPA ., 2005. Risk Analy sis for Alternative Refrigerant in Motor Vehicle Air Conditioning. US EPA, 2010 . Email from Yaidi Cancel, EPA to William Hill and Ward Atkinson, SAE*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 55 of 58 **Protection of Stratospheric Ozone: Alternative for**  **the Motor Vehicle Air Conditioning Sector under the Significant New Alternatives Policy (SNAP) Program**  **(Page 55**  **of 58**  **)** Interior Climate Control Committee re: Minimum recordkeeping on SAE J1739. August 16, 2010 White, C.S.; Humm, J.H.; Arm strong, E.D.; Lundgren, N.P.V., 1952. Human tolerance to acute exposures to carbon dioxide. Report No. 1 Six per cent carbon dioxide in air and in oxygen. Aviation Med. Oct. issue. pp439 - 455. As cited in Wong 1992. Wong, K.L. , 1992. Carbon Dioxide. Internal Report, Johnson Space Center in the Group. National Aeronautics and Space Administration, Huston TX. 1987 Yang, Y., S. Changnian, and M. Sun. , 1997. The effect of moderately increased CO 2 concentration on perception of coherent motion. Aviat Space Environ Med 68(3):187 - 191. List of Subjects in 40 CFR Part 82

Environmental protection, Administrative practicable procedure, Air pollution control, Reporting and recordkeeping requirements , Stratospheric ozone layer . Dated: _________________

_____________________

_____________________________________________ Lisa P. Jackson, Administrator*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 56 of 58 For the reasons set out in the preamble, 40 CFR Part 8 2 is amended as follows: **PART 8 2**  **- PROTECTION OF STRATOSPHERIC OZONE**  1. The authority citation for Part 8 2 continues to read as follows: **Authority:** 42 U.S.C. 7414, 7601, 7671 - 7671q. Subpart G -- Significant New Alternatives Policy Program 2. The first table in Appendix B to Subpart G of Part 8 2 is amended b y adding 1 new entry to the following at the end of the table to read as follows: Appendix B to Subpart G of Part 8 2 - Substitutes Subject to Use Restrictions and

Unacceptable Substitutes REFRIGERANTS - ACCEPTABLE SUBJECT TO USE CONDITIONS **Application Substitute**  **Decision Conditions**  **Further Information**

* * * * * * **** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 57 of 58 **Application Substitute**  **Decision Conditions**  **Further Information**

* * * * * * * CFC - 1 2 Motor Vehicle Air Conditioning (New equipment only) Carbon

dioxide ( CO 2 ) as a substitute for CFC - 1 2 Acceptable

subject to use conditions Engineering strategies and/or

mitigation devices shall be incorporated such that in the event of refrigerant leaks , the resulting CO 2 concentrations do not exceed: The short term exposure level (STEL) of 3% or 30,000 ppm averaged over 15 minutes in the passenger free space 34 ; and ; The ceiling limit of 4% or 40,000 ppm in the passenger breathing zone 35

. Vehicle manufacturers must keep records of the tests performed for a minimum period of three years demonstrating that CO 2 refrigerant levels do not exceed the STEL of 3% averaged over 15 minutes in the passenger free space, and the ceiling limit of 4% in the breathing zone. The use of CO 2 in MVAC systems must adhere to the standard conditions identified in SAE Standard J639 (2011 version) including: Installation of a high pressure system warning label; Installation of a compressor cut- off switch; and Use of unique fittings with: Outside diameter of 16.6 +0/- 0.2 mm (0.6535 +0/- 0.0078 inches) for the MVAC low - side; Outside diameter of 18.1 +0/- 0.2 mm (0.7126 +0/- 0.0078 inches) for the MVAC high side; and Outside diameter of 20.955 +0/- 0.127 mm (0.825 +0/- 0.005 inches) and right-hand thread direction for CO 2 refrigerant service containers . 36 Additional training for service technicians is recommended. In designing risk mitigation strategies and/or devices, manufacturers should factor in background CO 2 concentrations in the passenger cabin potentially contributed from normal respiration by the maximum number of vehicle occupants. Use of the standards SAE J1052, SAE J2772, and SAE J2773 is recommended as additional reference. Manufacturers should cond uct and keep on file Potential Failure Mode and Effects Analy sis in Design [Design FMEA], Potential Failure Mode and Effect Analysis in Manufacturing and Assembly Process [Process FMEA] on the MVAC as stated in SAE J1 739.*** E.O. 12866 Review _ Revised Version _ Do Not Cite, Quote, or Release During Review ***

Page 58 of 58 * * * * * [FR Doc. ] BILLING CODE 6560 - 50 - P

34 The passenger free space is the space inside the passenger compartment excluding the space enclosed by the ducting in the HVAC module . 35 Area inside the passenger compartment where the driver’s and passengers’ heads are located during a normal sitting position . Refer to SAE J1052 for information on determining passenger head position. 36 The refrigerant service containers fitting requirement applies only to refrigerant service containers used during servicing of the MVAC, in accordance with the provisions establi shed for MVAC servicing under 40 CFR part 82, subpart B .