Summary of Interagency Working Comments on Draft Language under EO 

12866 and EO 13563 Interagency Review. Subject to Further Policy Review.

Interagency Comments on U.S. Environmental Protection Agency (EPA) draft final rule titled,

“Protection of Stratospheric Ozone: Proposed New Listings of Substitutes; Changes of Listing 

Status; and Reinterpretation of Unacceptability for Closed Cell Foam Products under the 

Significant New Alternatives Policy Program; and Revision of Clean Air Act Section 608’s 

Venting Prohibition for Propane,” (RIN 2060‐AS80)

1. From the commenting agency’s perspective, this rule is a very helpful driver in our efforts to 

secure an HFC amendment in 2016 by showing that HFC alternatives are available, and that the 

US is delivering domestically to reduce HFC use and emissions. This rule would significantly 

help the negotiations if the proposal is out by mid-March, this would be far enough in advance 

of the April 4-8 Open-ended working group meeting that other countries would be aware of it 

and we can speak to the proposal at the meeting. Second, the commenting agency would ask 

that we make utmost efforts to finalize the rule by mid-September, in advance of the October 

10-14 Meeting of the Parties where the commenting agency hopes to adopt an HFC amendment.

EPA Response: We appreciate the commenter’s perspective and agree that there is value in 

issuing the NPRM ahead of the April 4-8 OEWG meeting. It would provide an opportunity for 

the United States to demonstrate the actions we are taking domestically. We also see the value 

in issuing the final rule ahead of the October MOP. 

2. Has EPA considered including window air conditioning units? Or are there other categories of 

equipment that EPA thinks should be included as well?

EPA Response: EPA has reviewed the SNAP end-uses considering the overall risk to human 

health and the environment of the various acceptable alternatives and knowledge of the 

availability and deployment of equipment using alternatives that pose lower overall risk. For 

window air conditioners, in April 2015, EPA found HFC-32, R-290 and R-441A acceptable 

subject to use conditions. We are not aware of any such units being sold in the U.S. market 

currently. Furthermore, recent changes in the UL Standard covering such products have placed 

on these acceptable refrigerants requirements that are stricter than the use conditions EPA 

established. The UL Standard effectively limits use of these flammable refrigerants to a small 

subset of room air conditioners. Because we have no evidence that alternatives have been 

identified that are viable for these units, EPA considers it premature to propose that other 

alternatives that pose lower risk are available in this end-use.

Lower-GWP refrigerants are acceptable in other end-uses; however, similar to window air 

conditioning units at this time we do not have evidence that those alternatives are viable for 

those particular end-uses. EPA will continue to study those end-uses and the availability of 

alternatives that pose lower overall risk to human health and the environment for possible 

changes of status in the future.

3. Table numbers refer to tables in the screening analysis for the following comments:

a. Aggregation in the screening analysis - EPA should not be considering the aggregated 

impacts on small entities to support its RFA certification. This rule is a series of 

separable provisions that do not interact with each other, so aggregation masks 

significant economic effects. In particular, working from table 19 of the screening 
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analysis, if considered separately, two of the product/uses regulated here appear to lead 

to significant economic impacts on a substantial number of small entities. 

EPA Response: Per EPA’s “Final Guidance for EPA Rulewriters: Regulatory Flexibility 

Act as amended by the Small Business Regulatory Enforcement Fairness Act” (2006), 

EPA makes a certification of no SISNOSE for a rule as a whole (i.e., aggregates across 

industries and or types of small entities). EPA does not make separate certifications for 

separate provisions of a single rule, even if the provisions are separable.

b. Annualization in the screening analysis - While annualization may be appropriate in 

cost-benefit analyses, it should not be used in screening analyses. Annualization 

assumes that a small business can effect a loan for the purposes of regulatory 

compliance at a rate of 7% over the annualization period. (In one case, EPA uses 20 

years. In another case, it uses 25 years. Neither would be available to a small business, 

even for productive investment in facilities.) Please express compliance costs in terms 

of capital (or one-time) costs and operating costs to help evaluate the likely economic 

impacts. 

EPA Response: EPA’s “Final Guidance for EPA Rulewriters: Regulatory Flexibility Act as 

amended by the Small Business Regulatory Enforcement Fairness Act” (2006) 

specifically states that “annualizing the compliance costs is appropriate when a stream 

of cash flows or a large capital expenditure is involved with compliance (see section 

2.6.2 on p.20).

c. Energy Efficiency Standards - The interaction between the DOE energy efficiency 

standards and this proposed rule are more significant than discussed and has the 

potential to significantly increase costs. It appears that the cost estimates in the 

screening analysis assumes that replacement with 450 and 513 will have no energy 

efficiency impacts. Are there any other sources for the assertion that 450 and 513 are 

drop-in replacements that require no upfront re-engineering or changes to maintain 

energy efficiency? 

EPA Response: EPA noted in SNAP Rule 20 that R-450A and R-513A were specifically 

designed to be a very close match in the properties and performance of HFC-134a. As 

such, EPA does not believe that the energy efficiency of a given unit will be significantly 

impacted by the choice of these refrigerants. Because the changes of status proposed 

here only affect new equipment, manufacturers will have ample opportunity to assess 

and, if desired, improve the efficiency of equipment using these alternatives. In fact, the 

similarity with HFC-134a is so good that manufacturers are currently offering 

equipment that are equally rated for either refrigerant (e.g., for chillers dual-rated for 

HFC-134a and R-513A, see http://www.trane.com/commercial/europe/be/en/aboutus/newsroom/press-releases/trane-sintesis.html and 

https://www.chemours.com/Refrigerants/en_US/assets/downloads/20160120-pressrelease-johnson-controls-opteon-xp10.pdfu). 
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For small entities, a short gap between energy efficiency standards and SNAP standards 

means that they either have to go through two engineering cycles on their products in a 

very short period of time or their compliance date for SNAP would, in effect, be the 

earlier date for energy efficiency standards. If the practical effect of the two rules 

together is an earlier compliance date, how does that affect EPA’s finding that there is 

enough time to meet the technical challenges of adopting substitutes? If engineering for 

both regulation has to be combined, then it would increase the costs.

EPA Response: Although EPA works under authorities different than DOE, and 

therefore our status change dates may differ from DOE compliance dates, EPA has 

considered the DOE energy conservation standards as part of our analysis of when 

products using alternatives may be available, and has proposed status change dates 

considering those standards. For those products that fall under DOE energy 

conservations standards (e.g., home refrigerator-freezers, some refrigerated food 

processing and delivery equipment, some equipment types applied in cold storage 

warehouses), EPA has considered the existing and likely future cycles of DOE standards, 

and believes the status change dates we have proposed line up reasonably well with 

DOE compliance dates. This will allow manufacturers to choose whether they wish to 

meet the two regulations in series—in which case the costs estimated by EPA would 

apply to meeting our proposed regulation—or whether they want to reduce costs by 

meeting them in a combined fashion. We expect that updated information regarding the 

DOE standards will become available during the comment period on the proposed rule 

and we will consider that information along with comments on this issue as we develop 

the final rule.

d. Cold Storage – The commenter has concerns about the certification for this sector. This 

section leaves the impression that the universe of small entities that produce packaged 

systems with fluorinated refrigerants would be significantly affected (i.e., 4 of 4). Table 

19 implies that all four of these entities would experience a significant economic impact. 

Advocacy encourages EPA to consider alternatives that would significantly reduce the 

burden on these four entities.

EPA Response: While EPA agrees it is appropriate to analyze impacts on different 

industries separately in order to consider alternatives that may alleviate some impact 

for sectors or industries where impact is greater, for purposes of certifying no SISNOSE, 

impacts of a rule are aggregated across sectors/industries/type of entity, and the 

certification decision is based on the aggregated impact (see section 2.7.3, pp.26-28). 

EPA does not make certifications by sector.

e. Spray – The commenter has significant concerns about the certification for this industry. 

Even though the number of small entities in the NAICS code is several hundred, the 

whole NAICS code is not the appropriate number against which to compare for the 

purposes of determining a “substantial number.” Considered as a separable part of this 

rulemaking, table 19 would imply that almost half of the small entities affected would 
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experience significant impacts. Since these impacts are presented as annualized over 25 

years, this may be a significant understatement of costs.

EPA Response: EPA has not compared the number of affected small businesses against 

all small businesses in the whole NAICS code. While EPA agrees it is appropriate to 

analyze impacts on different industries separately in order to consider alternatives that 

may alleviate some impact for sectors or industries where impact is greater, for 

purposes of certifying no SISNOSE, impacts of a rule are aggregated across 

sectors/industries/type of entity, and the certification decision is based on the 

aggregated impact (see section 2.7.3, pp.26-28). EPA does not make certifications by 

sector.

f. Repair and Maintenance - I’m not completely sure how this rule would impact repair 

and maintenance of equipment manufactured before the effective dates. Would a partial 

replacement of refrigerator parts and recharge with phased out HFC still be allowed? 

How are these service providers regulated? Are there any estimates of the size of this 

kind of repair market and the extent to which it extends the useful life of regulated 

products?

EPA Response: This rule would not impact repair and maintenance of equipment 

manufactured before the effective dates. As in the previous rule for change of status of 

certain substitutes, equipment manufactured before the change of status dates may 

continue to be serviced with the refrigerants undergoing a change of status. The 

proposed change of status would apply only to newly manufactured equipment.

4. The commenter conducts research and operations across a wide spectrum of technical areas 

and levels of readiness. In general, the commenter uses HFCs as replacements for ozonedepleting substances (ODSs) in numerous applications, including certain mission-critical 

applications for which appropriate substitutes have not been identified. These uses can include 

precision cleaning, foam blowing, and possibly other applications. Because of the dynamic 

nature of our Agency’s work, particularly as regards space flight programs currently being 

developed, it is not possible to identify all possible mission-critical uses of high-GWP 

substances, even the limited subset of materials and applications addressed in the proposed 

Significant New Alternatives Policy (SNAP) Program rule.

Two proposed provisions are of particular concern, as detailed below. 

a. Extension of the proposed narrowed use limit for spray foams by three years, to expire 

on January 1, 2025. EPA is proposing to list as unacceptable several HFC and HFC blend 

foam blowing agents for certain spray foam applications. EPA is also proposing an 

exception to this listing for military or space-and aeronautics-related applications when 

used in low pressure two-component and high pressure two-component spray foams. 

This exception would be a narrowed use limit expiring on January 1, 2022.
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As currently written, the proposed rule would allow the commenting agency to use 

through Calendar Year (CY) 2021 mission-critical HFC 245fa-based cryoinsulation spray 

foams being qualified for use on space flight hardware. These foams replace HCFC 

141b-blown foams, which in turn replaced CFC 11-blown foams in similar applications. 

Each of these successive foam replacement efforts took several years due to the 

challenging operational environment and the lengthy requalification process associated

with human rating. The commenting agency has begun planning a research program for 

our human-rated systems that would screen numerous foam chemistries as possible 

substitutes. However, since no single chemistry has yet been identified that can meet 

the rigorous technical and safety requirements of human-rated space flight systems, it 

could take several years to complete replacement work. Considering the length of the 

federal budgetary cycle and the length of time the commenter anticipates being needed 

to identify, develop, test and implement substitutes, the commenter does not expect to 

be able to deploy replacement foams in the proposed timeframe. Although the 

commenter is not certain how much time will be required for substitution work, the 

commenter believes an additional three years for this narrowed use limit should be 

adequate.

EPA Response: EPA agrees. We appreciate the additional information on specific steps 

required for military or space-and aeronautics-related applications. We will revise the 

discussion in the preamble to allow until January 1, 2025 for those applications under 

the narrowed use limit.

b. Exemption of spaceflight hardware and related support equipment from the proposed 

import ban on products composed of or incorporating closed cell foams made with 

unacceptable blowing agents.

EPA is proposing to apply the unacceptability determinations in this action for foam 

blowing agents, as well as all listings for foam blowing agents codified in the 

appendices to 40 CFR part 82 subpart G, to closed cell foam products and products 

containing closed cell foam. This would mean that closed cell foam products and 

products containing closed cell foams manufactured abroad and imported could not 

be used in the United States if the foam blowing agent was listed as unacceptable.

The commenting agency uses parts and components made abroad to meet 

challenging mission requirements and, in some cases, as part of international 

agreements with partners such as Japan, Canada, Russia, and the European Union. 

These components may comprise or incorporate closed cell foam products or 

products containing closed cell foams made with blowing agents listed as 

unacceptable. It is critical that the commenting agency be allowed to use parts and 

components that are qualified for spaceflight applications to minimize risk to our 

crews, vehicles and overall mission.

We request that EPA consider exempting spaceflight hardware and related support 

equipment from this proposed provision. This would allow continued use of parts 
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and components needed for mission safety and to meet the technical requirements 

of the commenter’s partners.

In addition, NASA has reviewed the recently updated draft language providing 

“narrowed use limits for military or space- and aeronautics-related applications” 

through CY 2024 for certain refrigerants used in centrifugal chillers and positive 

displacement chillers. We concur with this updated draft language.

EPA Response: In response to the commenting agency’s request, we are proposing to 

revise the change of status date from January 1, 2022 to January 1, 2025 when HFCs 

become unacceptable in foam blowing end-uses for space and aeronautic-related uses. 

This will provide additional flexibility to the commenting agency for all foam blowing 

end-uses. For space and aeronautics-related uses, the extension of unacceptability 

determinations to foam products containing the unacceptable foam blowing agent 

would apply only to products manufactured after January 1, 2025.

5. Much of the supporting analysis referenced by EPA as contained within contracted research 

reports was not available to the commenting agency and thus, we were unable to determine the 

underlying assumptions that went into the analysis. From the commenting agencies’

perspective, there are several areas where it appears (under cursory review) that the 

occupational exposure perspective may have been insufficiently and/or inappropriately 

considered. For example:

a. In many instances, the EPA analysis relies on AEGL values for short-term exposure and 

does not use NIOSH IDLH values. This occurs in both occupational and non-occupational 

analysis but given that many workers commute or work in affected vehicles for 

significant time periods, the “consumer” analysis needs to also consider occupational 

exposure criterion. 

EPA Response: It is not clear which substitute or end-use the comment pertains to. We 

are unaware of a NIOSH IDLH value for HFO-1234yf or 2-BTP. In the case of propane, 

EPA initially considered using the IDLH value of 2,100 ppm (30-minute TWA), but 

decided not to use the IDHL because it is based upon flammability concerns (i.e., set at 

10% of the lower explosive limit of 2.1%). Instead, we decided to use the AEGL-1 (30-

min) in our analysis of toxicity of propane because the AEGL-1 is based on toxicity 

information. Further, the AEGL-1 value is appropriate for the general population. For ice 

machines and water coolers, the end-use analysis considers scenarios where a 

consumer could be exposed as well as a worker (e.g., ice machine used in a restaurant). 

EPA has analyzed flammability concerns separately from toxicity based upon an 

instantaneous release of refrigerant rather than upon a 30-minute TWA exposure, such 

as would be needed to compare to a 30-minute TWA IDLH. 

3/17 Interagency Follow-up Comment: 

When discussing alternatives solely from a toxicity perspective – we concur with this 

approach. The end-use analysis details are not available to the reviewers and is only 
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loosely referenced in the NOPR. It is not clear if commercial-sized refrigeration and ice 

making equipment were evaluated under non-restaurant scenarios such as in a small 

bar that may not have a kitchen hood exhaust. If not considered, then further analyses 

should be performed since such higher charges, lower ventilation rate scenarios could 

alter the model outcomes. 

EPA Response: EPA will take comment in the preamble on the risk screens, their 

assumptions, and the exposure limits used in our evaluation.

b. EPA’s occupational exposure analysis was consistently limited to service technicians 

and apparently did not consider the potential occupational exposures that could result 

to workers in numerous industries affected by the proposed rule, but most notably 

workers in transportation, public (to include fire/rescue/police), healthcare and service 

sectors.

EPA Response: The only workers that normally would work directly with refrigerant 

would be technicians or individuals who evacuate refrigerant from the equipment 

during recycling or disposal, and EPA analyzed both of these situations under the 

description of “occupational exposure.” However, EPA also evaluated exposure in the 

case where there is a leak from the equipment while it is in use. In these analyses, EPA 

considered consumer exposure and personnel exposure, such as to a restaurant worker 

working near a commercial ice machine or water cooler or a laboratory worker working 

near a very low temperature freezer. For use of HFO-1234yf in motor vehicle air 

conditioning, EPA considered exposure to professional technicians, vehicle occupants, 

and first responders (i.e., fire/rescue/police). EPA looked at both exposure to the 

refrigerant itself as well as exposure to potential combustion byproducts (p.171-172 & 

176 of the preamble) and concluded that HFO-1234yf does not pose greater risk with 

regard to HF generation than other available or potentially alternatives, including risk 

to workers.

c. When considering flammability issues, they rely on Lower Flammability Levels (LFL) 

(and apparent assumptions of even mixing throughout spaces) as opposed to the 

traditional 10% of Lower Explosive Limit (LEL) criteria. 

EPA Response: EPA’s SNAP program has traditionally analyzed flammability risks by 

considering an instantaneous release of the substitute and comparing it to the lower 

flammability limit (LFL). We start by assuming that refrigerants that are denser than air, 

such as propane, will pool near the floor, and that 95% of the refrigerant charge will be 

in the lowest 0.4 m (1.3 ft) of a room. We also look to available literature for 

conservative but reasonable assumptions about ventilation rates, as well as using 

available information on room sizes and charge sizes. If a substitute’s instantaneous 

concentration exceeds the LFL, then we reconsider the conservativeness of the 

assumptions, and may consider situations where complete mixing is reasonable (e.g., if 

building codes require a certain ventilation rate).
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EPA understands that NIOSH has sometimes used a value of 10% of the LEL when 

establishing 30-minute IDLH values for the workplace for certain highly flammable 

substances (e.g., propane). However, we are unfamiliar with risk assessments of specific 

situations that use such a criterion. It is also our understanding that OSHA regulations 

require concentrations of flammable substances be kept to no more than 25% of the LFL 

in the workplace. Thus, we do not agree that there is a “traditional” value used 

throughout the federal government for addressing and assessing flammability risks.

3/17 Interagency Follow-up Response to first paragraph: 

Under still air conditions this seems plausible, but in semi-confined environments 

where this equipment is often placed, (often more than one piece at a time) with faninduced airflows and hot equipment whose heat exchangers induce convective heat rise, 

a still-air assumption is probably not practical. Under these scenarios, room sizes and 

room ventilation rates may often be disassociated with gas behavior near the 

equipment. These scenarios should be investigated using actual experimental results as 

opposed to theoretical models that require generalized input assumptions.

Regarding “If a substitute’s instantaneous concentration exceed the LFL...”: From a human 

safety perspective, the LFL itself is not an acceptable pass/fail criterion for potential 

flammable environments. 

It is important to note that a NIOSH IDLH value is not a 30-minute time-weighted 

average (TWA). It is a ceiling value that represents a concentration for which “EVERY 

EFFORT SHOULD BE MADE TO EXIT IMMEDIATELY” (emphasis not added by 

reviewers) Please see: http://www.cdc.gov/niosh/npg/pgintrod.html

3/17 Interagency Follow-up Response to second paragraph:

We concur with the EPA’s comment that the 10% of LEL criterion by itself is not the sole 

“traditional” criterion for determining when an environment potentially exposed to 

flammable vapors is “safe”. In hindsight, we should have said, “...as opposed to the 

traditional 10% or 25% of Lower Explosive Limit (LEL) safety criteria for potentially 

flammable environments that is cited by NIOSH, OSHA and NFPA.” Either of these 

criterion however, are a much more realistic safety concentration target than the 

current NOPR’s use of 100% of the LFL as the safe threshold. 

Regarding the EPA response sentence “It is also our understanding that OSHA 

regulations require...”:

1) OSHA defines Hazardous Atmospheres as including “Flammable gas, vapor, or 

mist in excess of 10 percent of its lower flammable limit (LFL).” 

http://webapps.dol.gov/elaws/osha/confined/definitions.asp#hazardous.
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2) There is logical basis within NFPA (and by ref, some OSHA codes) to use the 25% 

of LEL for non-confined areas. Either of these options (10% or 25%) are a much 

safer alternative for a pass/fail criterion than the LFL itself. 

EPA response: EPA will take comment in the preamble on the risk screens, their 

assumptions, and the flammability limits used in our evaluation.

d. EPA needs to add minimum enclosure volume requirements as a proposed use 

condition for placement of new equipment that uses flammable refrigerants. Ice 

machines, vending machines and water coolers are often placed within custom wall 

cubicles that would exacerbate the flammability hazards associated with potential leaks 

and these size restrictions do not appear to have been adequately considered within 

EPA’s analysis. 

EPA Response: Rather than proposing to add a use condition, EPA will take comment in 

the preamble on the risk screens and their assumptions. Based on currently available 

information, we think that the room sizes used in our risk screen indicate there would 

not be an unacceptable risk of fire or explosion provided that the charge size is limited 

to 150 g. However, if further information becomes available during the public comment 

period that might cause us to change our assumptions, we may consider setting a use 

condition.

3/17 Interagency follow-up comment: We appreciate the concurrence. Upon 

additional reflection, the minimum enclosure volume requirements should also 

probably be based on a “per piece of equipment” ratio since many such areas could have 

multiple pieces of equipment using the same refrigerant.

Given these assumptions, sq-ft of floor area seems to be a more applicable criteria than 

room volume. Nevertheless, our calculations, following the EPA-provided assumptions,

determined that this may not be a sufficiently large space. (Please see sample 

calculation for minimum room volume below)”. 

Regarding “...or at least 15 m3 for equipment with a charge of 100 g or less,” similar 

concerns exist for this Room volume: charge size ratio as to those stated immediately 

above

Sample Calculation for Minimum Room Volume (Floor Area) Discussion:

Given: 

(1) EPA/NOPR proposed limit of room volume of 22 m3

(2) EPA/NOPR assumption that 95% of propane charge will settle in lowest 0.4 meters of 

floor area

(3) LEL for propane = 21000 ppm (NIOSH pocket guide -

http://www.cdc.gov/niosh/npg/npgd0524.html )

(4) 1 ppm propane/air = 1.8 mg/m3 propane/air (NIOSH pocket guide)
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Assumption: 

(1) Room height in EPA/NOPR proposed room volume is 2.44m (8’) [Note: A taller room 

height would be an even worse scenario)

Calculations: 

(1) Floor area = V/h = 22 m3 / 2.44m = 9m2

(2) Vol of propane-contaminated atmosphere = 9m2 x 0.4m = 3.6 m3

(3) 95% of 150g charge = .95x150x1000 = 142500 mg of propane

(4) Conc of propane in lower rom volume = 142500 mg/ 3.6 m3 = 39583 mg/m3

(5) 39583 mg/m3 / ((1.8 mg/m3)/ppm) = 21991 ppm of propane**

** This value is above the LEL for propane, over 4 times the 25% of LEL (5250 ppm) criterion 

and over 10 times the 10% of LEL criterion. The NIOSH reviewers recommend that the 

minimum floor volume per piece of propane refrigerant equipment be increased to at least 

comply with the 25% of LEL criterion. However, even this increase may not be sufficient (see 

additional comment below). 

Additional Comment: While it is an informative exercise, a potential fault in this approach is the 

assumption that the propane will dissipate across the entire floor area. As we know, this 

equipment tends to be placed into wall cubicles, under countertops, between cabinets and/or 

between other pieces of equipment (that may not have similar UL protections as the refrigeration 

compressors that use flammable refrigerants). Under these real-world installation conditions –

the resulting propane concentration under the identified release scenario would be even higher 

and a serious potential hazard given all of the ignition sources in these areas. 

EPA Response: EPA will take comment in the preamble on the risk screens and their 

assumptions.

e. Combustion byproduct analysis for HFO-1234yf only focused on hydrogen fluoride 

whereas recent research ((http://www.en.unimuenchen.de/news/newsarchiv/2014/kornath_refrigerant.html) seems to indicates 

carbonyl fluoride (much more toxic) should also be considered. 

EPA Response: The amount of carbonyl fluoride produced when HFO-1234yf 

decomposes or burns is small and is comparable to that for HFC-134a. For both 

compounds, carbonyl fluoride quickly reacts with moisture and decomposes to HF and 

CO2. 

f. In the combustion byproduct analysis, AEGL values were again referenced for potential 

occupational exposure scenarios where ILDH values are more applicable and in this 

case, would likely have led to a different conclusion. 

EPA Response: Exposure to combustion byproducts of HFO-1234yf is anticipated to 

occur only when the refrigerant combusts and the combustion byproducts are carried 

into the passenger cabin. If a driver or passenger is in a vehicle with a fire under the 

hood and is exposed to smoke and the byproducts of combustion of refrigerant, he or 
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she is likely to exit the vehicle as quickly as possible, and certainly in far less than 30 

minutes. Thus, a higher AEGL-2 value of 95 ppm over 10 minutes is more applicable, 

rather than a longer-term, lower exposure limit for HF such as the IDLH of 30 ppm over 

30 minutes or the AEGL-2 of 34 ppm over 30 minutes.

3/17 Interagency follow-up comment: 

Regarding “likely to exit the vehicle as quickly as possible...”: assumes that the person is 

able to exit, which is often not the case.

“...a higher AEGL-2 value of 95 ppm...”: NIOSH Recommended Exposure Limits (RELs) for 

hydrogen fluoride include a 15-minute ceiling of 6 ppm (same as the OSHA STEL) and 

an IDLH value of 30 ppm. As indicated in our other responses, the IDLH value is NOT a 

30-minute TWA, but rather is an exposure value that should result in immediate 

evacuation. (Please see NIOSH Pocket Guide entry: 

http://www.cdc.gov/niosh/npg/npgd0334.html ).

It is noted that in the two EPA-cited experimental investigations (see next comment) of 

potential hydrogen fluoride exposures in the cab of a vehicle, the above-mentioned HF 

concentration values (6 ppm & 30 ppm) were exceeded in both experiments, and 

significantly so in 1 of 2 of the experiments.

EPA Response: This section is a reference to risk assessment work performed by a 

cooperative research program (CRP) of SAE International, an international standardsetting body. We have relied upon this work in EPA’s earlier listing of HFO-1234yf for 

light-duty passenger vehicles and trucks and have no new information indicating that 

there is a problem with this approach. EPA considers the SAE CRP’s approach to 

evaluating risk of HF to be sufficiently protective.

g. Low-to-no repetition data points (with insufficient information provided regarding 

sample protocol, collection point, etc.) appear to have been used to make definitive risk 

conclusions without considering statistical variability and the impact it could have on 

subsequent safety conclusions. 

EPA Response: It is not clear from the comment what substitute, end-use, or test the 

commenting agency is referring to. In general, EPA’s screening analyses for flammability 

and toxicity risks in this rule are based upon measurements when available, or exposure 

modeling using a box model if measured data are not available (see p. 63 of the 

preamble). EPA also uses any modeled or empirical information provided by submitters 

of the substitutes under review or other available industry data, which in some cases 

has included measured data (e.g., measurements of HF concentrations during 

decomposition of HFO-1234yf from the SAE Cooperative Research Program mentioned 

on p. 175 of the preamble).
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3/17 Interagency Follow-Up Comment: The comment applies to the previous 

discussion on combustion byproducts (specifically HF) as well as the two “extreme 

condition” tests mentioned towards the bottom of page 174 of the NOPR. 

Regarding the last part of the response“...(e.g., measurements of HF concentrations 

during decomposition of HFO-1234yf from the SAE Cooperative Research Program 

mentioned on p. 175 of the preamble):.” Note that there appears to be a typo in the 

estimated risk cited from the SAE CRP1234-4 report. From page 174 of updated NOPR, 

“Based on the updated analysis, the estimated overall risk of vehicle fire exposure 

attributed to use of R-1234yf is conservatively estimated at 3x1012 events per vehicle 

operating hour.” We believe the exponent is missing a minus sign and the estimate is 

intended to be “3x10 -12”

EPA Response: Thank you for the correction. EPA will change this in the preamble.

h. There is a strong reliance upon UL listing requirements (especially as they relate to 

refrigerant charge limits) without providing the details of assumptions made by the UL 

in determining that such limits were safe. We cannot verify the accuracy of this 

approach. Our own calculations identified very plausible scenarios where the proposed 

refrigerant charge limits could create atmospheres in excess of 10% of LEL under 

catastrophic release scenarios discussed in the notice of proposed rulemaking. 

EPA Response: EPA relies on the consensus-based standards from UL as directed under 

the National Technology Transfer and Advancement Act of 1995 and OMB Circular A119, Federal Participation in the Development and Use of Voluntary Consensus Standards 

and in Conformity Assessment Activities. The UL standards include safety provisions that 

are independent of the specific charge size. For example, the UL standards require 

testing of equipment to ensure the leaked amount of refrigerant will remain well below 

the LFL (e.g., sections SB5.1 of UL 471 for commercial refrigerators and freezers, SA 5.1 

of UL 563 for ice makers). In the leak test, the measured concentration of leaked 

refrigerant is prohibited from exceeding 75% of the LFL at all times during testing and 

is prohibited from exceeding 50% of the LFL for any period exceeding 5 minutes. 

Information is not available on the assumptions used by UL’s consensus-based 

standard-setting committees in selecting the charge size limit of 150 g. We note, 

however, that this charge size limit has been widely adopted in Europe for stand-alone 

equipment in locations that the public can access and is also a requirement in many 

international standards (e.g., IEC standards). 

EPA’s risk screening analyses contain specific assumptions about factors such as 

effective room size, ventilation rates, charge sizes, length of release of refrigerant and 

whether leaked refrigerant is assumed to be evenly dispersed in a room or is 

concentrated close to the floor. The results of these analyses are described in the 

preamble.
13

6. The provision concerning the 2022 phase-out of HFC-134a in centrifugal and positive 

displacement compressor chillers will adversely impact national security unless narrowed use 

limits are crafted for our mission-critical applications in marine vessels. The commenting 

agency is working closely with industry partners that produce this mission-critical hardware to 

identify and eventually qualify suitable lower-GWP alternatives. However, the lower-GWP 

alternatives currently being offered or proposed for use in commercial chillers either do not 

meet the commenting agency's military-unique requirements or will require longer timeframes 

to test for military suitability, and then redesign, qualify, and procure new chillers for the 

agency’s shipbuilding programs. 

EPA Response: EPA is proposing a narrowed use limit that would allow use of HFC-134a in 

centrifugal and positive displacement compressor chillers beyond January 1, 2024, for certain 

military applications, specifically marine vessels.

7. 3/18 Comment: The commenting agency recently identified a possible chiller issue with the 

2025 date. The agency plans to use HFC 134a as a coolant on the Orion capsule while it is on 

the ground. A chiller will circulate the coolant until launch. If this type of use would be 

unacceptable with the regulatory language as written, we would appreciate it if EPA would 

consider including space vehicle applications in the chiller narrow use limit. The commenting 

agency appreciates EPA’s flexibility to consider unique NASA mission applications.

EPA Response: EPA will propose a narrowed use limit for R-134a and R-404A in new 

centrifugal chillers and positive displacement chillers for use in human-rated spacecraft.

8. 3/23 Comment: Will EPA add a reference in the New Cold Storage Warehouse section that 

discusses DOE regulatory efforts regarding Walk-In Coolers and Walk-In Freezers? The 

following language was paraphrased from DOE’s technical amendments final rule 80 FR 69837 

(November 12, 2015) that was issued in response to litigation on DOE’s final rule from June 3, 

2014. The compliance timing of the reconsideration rule has not yet been publicly announced, 

but DOE indicated that the compliance date would likely be at the end of 2019. 

DOE issued a final rulemaking on June 3, 2014 (79 FR 32049) that set nineteen energy 

conservation standards for walk-in coolers and walk-in freezers with a compliance date of June 

5, 2017. Due to litigation regarding this rulemaking, DOE vacated six of those standards for 

refrigeration systems and is currently engaged in a negotiated rulemaking to address the 

standards as referenced in the agency’s technical amendments final rulemaking 80 FR 69837 

(November 12, 2015). 

EPA Response: EPA is adding this language to the preamble in the section discussing the 

relationship between this rule and other federal rules:

DOE issued a final rulemaking on June 3, 2014 (79 FR 32049) that set nineteen 

energy conservation standards for walk-in coolers and walk-in freezers with a compliance 

date of June 5, 2017. Due to litigation regarding this rulemaking, DOE vacated six of those 

standards for refrigeration systems and is currently engaged in a negotiated rulemaking to 

address the standards as referenced in the agency’s technical amendments final rulemaking 
14

80 FR 69837 (November 12, 2015). Consistent with DOE’s rule, which defines walk-in 

coolers and walk-in freezers as having a total chilled storage area of less than 3,000 square 

feet, EPA considers such equipment to fit within the retail food refrigeration end-use, rather 

than the cold storage warehouse end-use. Thus, we consider there to be no regulatory 

overlap between this proposed rule and the DOE energy conservation standards for walk-in 

coolers and freezers. 

9. 3/23 Comment: NASA requests that EPA add spacecraft applications as “acceptable subject to 

narrowed use limits” after January 1, 2025 for centrifugal chiller and positive displacement 

chiller end uses of HFC 134a and R-404A. We appreciate EPA’s flexibility to consider unique 

NASA mission-critical applications. Below is the justification language provided by NASA 

concerning their Orion mission. Will EPA include and request comment as they may revise 

their request prior to issuing the final rule?

NASA has recently identified an additional issue related to EPA’s proposed provisions limiting 

the use of coolants, including HFC 134a and R-404A, in chillers. The agency anticipates being 

able to transition chillers to acceptable coolants for most uses. However, NASA plans to use 

HFC 134a and R-404A to provide cooling to human-rated spacecraft during ground-based 

assembly, integration and test operations, and launch. The cooling of sensitive human-rated 

electrical equipment is critical to the spacecraft technical performance and crew safety. NASA 

programs use specialized ground coolant systems to provide heat transfer during certain 

ground operations. These coolant circulation systems use HFC 134a and R-404A to meet the 

program’s stringent performance and material compatibility requirements. Alternate 

substances listed as acceptable under the SNAP program may not provide appropriate heat 

transfer, material compatibility, stability in the test environment, and other critical properties. 

Considering that identification, testing, and implementation of materials to be used in humanrated spaceflight programs routinely take several years due to the challenging operational 

environment, lengthy qualification process associated with human rating, and the federal 

budgetary cycle, NASA does not expect to be able to deploy substitute coolants in EPA’s 

proposed timeframe.

EPA Response: EPA will propose a narrowed use limit for R-134a and R-404A in new 

centrifugal chillers and positive displacement chillers for use in human-rated spacecraft.