Found this on the Federal Register.....
II. Request for Information on Refrigerants for Motor Vehicle Air
Conditioners
EPA requests information on the refrigerants Enviro-Safe, Red Tek, Maxi-Frig, ES-12A, and Auto Cool. EPA has received numerous inquiries regarding the SNAP acceptability of the above refrigerants for use in motor vehicle air conditioners (MVACs). Materials disseminated through mailings and the internet (Air Docket A-91-42, item IX-B-60) have made consumers question whether the products listed above are acceptable substitutes under the SNAP program for CFC-12 (R12 or freon) and other ozone-depleting CFC-12 substitutes. Under Section 612(e) of the CAA, any person who produces a substitute for a CFC is required to submit information to EPA at least 90 days before the substitute is introduced into interstate commerce.
The refrigerants listed above have not been submitted to EPA for review under the SNAP program. Therefore, the Agency believes that they cannot be sold as replacements for CFC-12 or other ozone-depleting CFC substitutes in MVACs.
Additionally, based on advertising materials, Material Safety Data Sheets (MSDSs) and independent laboratory testing (Air Docket A-91-42, item IX-B-60), EPA believes the refrigerants listed above may be flammable hydrocarbon-based blends. In June 1995, flammable refrigerants were listed as unacceptable as substitutes for CFC- 12 in MVACs because a comprehensive risk assessment on the use of flammable refrigerants had not
been submitted to EPA (60 FR 31092). EPA welcomes the submission of such a risk assessment.
However, until EPA receives sufficient information on the potential risks of flammable refrigerants in MVACs, all flammable refrigerants are unacceptable as substitutes for CFC-12 and ozone-depleting freon substitutes in MVACs, unless specifically listed as acceptable.
Consumers should also be aware that the following 19 states ban the use of flammable refrigerants in MVACs:
Arkansas, Arizona, Connecticut, Florida, Idaho, Indiana, Iowa, Kansas, Louisiana, Maryland, Nebraska, North Dakota, Oklahoma, Texas, Utah, Virginia, Wisconsin, Washington, and the District of Columbia. For further information about flammable refrigerants, see EPA's web site
(http://www.epa.gov/spdpublc/title6/snap/hc12alng.html).
Since ES12a is not listed on the EPA approved site I would assume that it has not been submitted for testing, thus making it illegal to use as an R12 replacement