Another step for HFO-1234yf?

By Jim Taylor, Editor MACS ACtion Magazine

Since the new gas is fairly benign in the atmosphere, it does not contribute to smog and ground-level pollution. For this reason, EPA is proposing to exempt the refrigerant (and its sister HFO-1234ze, used for foam blowing and insulation) from the federal VOC rules. The following text is excerpted (and trimmed) from the Proposed Rule in the Federal Register, posted October 17th of this year. It’s interesting reading, particularly in the last paragraphs.


“The EPA is proposing to revise the agency’s definition of volatile organic compounds (VOCs) for purposes of preparing state implementation plans (SIPs) to attain the national ambient air quality standards  for ozone. This proposed revision would add 2,3,3,3-tetrafluoropropene (also known as HFO–1234yf) and trans-1,3,3,3- tetrafluoropropene (also known as HFO–1234ze) to the list of compounds excluded from the definition of VOC on the basis that these compounds make a negligible contribution to tropospheric ozone formation.
This proposed rule is applicable to all manufacturers, distributors, and users of these chemical compounds. Specifically, the use of these compounds as aerosol propellants, blowing agents, or refrigerants, or any other use in which they would substitute for chlorofluorocarbons, hydrochloro-fluorocarbons, or their  substitutes, is subject to restrictions under the Significant New Alternatives Policy (SNAP) program.

The SNAP program has issued a final approval for HFO-1234yf as a substitute for use in the motor vehicle air conditioning end-use as a replacement for ozone depleting substances and final approvals for HFO-1234ze as a suitable foam and refrigerant substitute and as a propellant.  Furthermore, HFO–1234yf is subject to a Significant New Use Rule (SNUR).

Some background: Tropospheric ozone, commonly known as smog, is formed when VOCs and nitrogen oxides (NOX) react in the atmosphere in the presence of sunlight. Because of the harmful health effects of ozone, the EPA and state governments limit the amount of VOCs that can be released into the atmosphere. The VOCs are those organic compounds of carbon which form ozone through atmospheric photochemical reactions.

Different VOCs have different levels of reactivity—that is, they do not react to form ozone at the same speed or do not form ozone to the same extent. Some VOCs react slowly, or form less ozone; therefore, changes in their emissions have limited effects on local or regional ozone pollution episodes. It has been the EPA’s policy that organic compounds with a negligible level of reactivity should be excluded from the regulatory definition of VOC so as to focus control efforts on compounds that do significantly increase ozone concentrations. The EPA also believes that exempting such compounds creates an incentive for industry to use negligibly reactive compounds in place of more highly reactive compounds that are regulated as VOCs. The EPA lists these negligibly reactive compounds in its regulations and excludes them from the definition of VOC.

Compounds that are less reactive than, or equally reactive to, ethane under certain assumed conditions may be deemed negligibly reactive and therefore suitable for exemption from the regulatory definition of VOC. Compounds that are more reactive than ethane continue to be considered VOCs for regulatory purposes and therefore subject to control requirements. The selection of ethane as the threshold compound was based on a series of smog chamber experiments that underlay the 1977 policy.

In this case, the agency has examined available information on the risks to human health and the environment and applicability of other regulatory programs.   Honeywell, Inc. submitted a petition to the EPA on June 29, 2009, requesting that HFO–1234yf  be exempted from VOC control based on its low reactivity relative to ethane. The petitioner indicated that HFO–1234yf may be used as a refrigerant for refrigeration and air-conditioning. [The company submitted a similar petition to exempt HFO–1234ze.]

Honeywell also indicated that it expects HFO–1234yf to be widely used as a replacement for HFC–134a in motor vehicle air-conditioners, and that HFO–1234yf has been specifically developed for this purpose. Honeywell argues that as a replacement for use in motor vehicle air conditioners there will be an environmental advantage in that the global warming potential  of HFO–1234yf is 4,  substantially lower than the GWP for HFC–134a (100- year GWP = 1430) which HFO–1234yf is designed to replace.

Honeywell submitted several documents, including several peer-reviewed journal articles, to support this petition. The EPA requested additional toxicity testing and issued the SNUR for HFO–1234yf. The EPA has received and is presently reviewing the results of the additional toxicity testing. The EPA continues to believe that HFO–1234yf, when used in new automobile air conditioning systems in accordance with the use conditions under the SNAP rule, does not result in significantly greater risks to human health than the use of other available substitutes.

The use conditions in the SNAP approval have the effect of making it illegal to use HFO–1234yf in the air conditioning systems of heavy-duty trucks, refrigerated transport, or off-road vehicles such as agricultural or construction equipment. The use restrictions also have the effect of making use of the compound other than by manufacturers of automobiles and light-duty trucks or by commercial automotive service centers either illegal or highly unlikely.

While use by vehicle owners is not illegal, the SNAP conditions prevent the sale of HFO–1234yf in containers of the size that would be attractive to individual vehicle owners, and also include requirements for special connecting equipment for the large containers that are legal for sale. In addition, as described later in this notice, under a recent Significant New Use Rule anyone planning to distribute HFO–1234yf for use by a consumer would be required to notify the EPA before doing so.”

The Mobile Air Conditioning Society’s blog has been honored as the best business to business blog in the Automotive Aftermarket by the Automotive Communications Awards and the Car Care Council Women’s Board!

When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.

If you’re a service professional and not a MACS member yet, you should be, click here for more information.

You can E-mail us at or visit to find a Mobile Air Conditioning Society member repair shop in your area. Visit to find out more about your car’s mobile A/C and engine cooling system.

The 32nd annual Mobile Air Conditioning Society (MACS) Worldwide Convention and Trade Show will take place January 18-20, 2012 at the Rio All Suite Hotel and Casino in Las Vegas, NV.


About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues.
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