In a direct final rule, the U.S. Environmental Protection Agency (EPA) has amended the definition of volatile organic compounds (VOCs) by adding SolsticeTM 1233zd(E) to the list of compounds excluded from that definition. 

Developed by Honeywell, Inc., Solstice 1233zd(E) (chemical name trans 1-chloro-3,3,3-trifluoroprop-1-ene) is used primarily in blow-on insulting foam; the chemical is also used in the manufacture of refrigerants.

The EPA believes its policy to exclude compounds from the regulatory definition of VOCs serves as an incentive for industry to use negligibly reactive compounds that contribute less to the formation of tropospheric ozone in place of more highly reactive compounds subject to regulation.

Ground-level ozone

Honeywell’s primary environmental sales pitch is that SolsticeTM 1233zd(E) has low global warming potential (GWP) when compared to hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) used in blowing agents.  However, the company also petitioned the EPA to remove Solstice 1233zd(E) from the list of VOCs that are regulated because of their high level of reactivity with nitrogen oxides (NOx) in the presence of sunlight to form tropospheric ozone (smog).

Hence, EPA’s current action applies only to the VOC definition used in state implementation plans (SIPs) developed to attain the National Ambient Air Quality Standards (NAAQS) for tropospheric ozone under the Clean Air Act.  The EPA has extended the VOC exemption to other uses of Solstice 1233zd(E), including as a solvent and as a refrigerant in commercial chillers and waste heat recovery systems. 

SNAP program

Also, in August 2012, the EPA found Solstice 1233zd(E) acceptable under the federal Significant New Alternatives Policy (SNAP) program for use as a foam blowing agent in certain products, as a refrigerant in new centrifugal chillers, and as an aerosol solvent.  The SNAP program approves alternatives to ozone-depleting substances (ODSs) that damage the earth’s protective stratospheric ozone layer.  Other uses of Solstice 1233zd(E) under the SNAP program are still being reviewed. 

Regarding climate change, the EPA agreed with Honeywell’s assertion that Solstice 1233zd(E) has a lower or comparable GWP than other acceptable substitutes for ODSs with the same end uses.

Ethane comparison

The Agency’s regulatory process for excluding a compound from regulation as a VOC involves comparing the reactivity of the compound to the reactivity of ethane.  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 definition of a VOC. 

Applying the results of the tests in a smog chamber, the EPA concluded that Solstice 1233zd(E) is less reactive than ethane under multiple metrics the Agency uses to compare the reactivity of a compound to that of ethane. 

EPA’s direct final rule exempting Solstice 1233zd(E) from the definition of a VOC was published in the February 15, 2013, FR.