Cover Letter for HC-12a ® Petition Response
This letter and its attachment comprise EPA's response to the December, 1995 petition from OZ Technology requesting that EPA find HC-12a acceptable and HFC-134a unacceptable. The letter discusses general principles of flammability risk, while the attachment responds in a very detailed manner to the documents submitted with the petition. The full response is 30 pages long and may be obtained from the Air and Radiation Docket at 202-260-7548. The docket number is A-91-42 and the file number is VI-C-17. It is also available in WordPerfect 5.1 format (120K). The petition was not submitted electronically, so it is not available online.
N. 10900 Howell Road
Rathdrum, Idaho 83858
Registered Mail; receipt requested
Dear Mr. Lindgren:
Thank you for your petition, dated December 5, 1995, requesting that 1) EPA change the status of HC-12a under the SNAP program from unacceptable to acceptable, and 2) EPA change the status of HFC-134a under the SNAP program from acceptable to unacceptable. In reviewing this petition, EPA considered the documents to which it responds in this petition, as well as all information previously submitted regarding HC-12a, OZ-12 and HFC-134a.
For the reasons stated in the enclosed attachment, EPA denies this petition. In summary, none of the documents submitted as part of this petition adequately addresses the use of HC-12a as a CFC-12 substitute. While some documents answer a limited number of questions, they all neglect one or more of the following aspects of flammability risk:
1. Risk assessment is a necessary tool
The key measure of risk posed by flammable refrigerants is a scientifically valid, comprehensive risk assessment. Such an assessment must accurately reflect potential leak scenarios, potential ignition sources, the likelihood of ignition, the consequences of ignition or explosion, and potential measures to mitigate the risk. None of the documents submitted with this or earlier petitions represents such a risk assessment. Without such an assessment, no positive statements can be made about the actual risk flammable refrigerants pose to people using them. Subjective measures, experiments that do not reflect actual systems, and questionable science do not allow for a credible estimate of risk posed by the flammability of HC-12a.
2. Flammability risk differs with new system design versus
New systems can be designed to adequately address the risk of using flammable refrigerants. Existing systems were never intended to use such refrigerants, and therefore do not specifically protect consumers from that flammability. EPA requires a risk assessment for all use of flammable refrigerants, but their use in existing, unmodified systems requires special vigilance. No refrigeration systems (outside a limited number of industrial refrigeration systems), and no air conditioning applications, widely use flammable refrigerants in the US. Therefore, system owners (including car owners), service and disposal personnel, and fire fighting personnel do not expect to find flammable refrigerants in these systems. EPA must ensure that such use is safe, including the widespread dissemination of safe handling practices, before listing HC-12a or any flammable refrigerant as acceptable. Risk assessments for existing uses must reflect conditions found in the US today, rather than systems used in Europe or elsewhere in the world. For example, US refrigerators are much larger than the hydrocarbon-based systems found in Europe. A risk assessment for this end-use must address the larger system.
3. Flammability risk depends on the end-use and the
It is inappropriate to extrapolate from one end-use to another, or from one refrigerant to another. End-uses differ greatly in operating conditions. For example, automobiles are driven at high speeds and frequently collide with each other and other objects. The condenser on automobiles is immediately behind the grille, where it is highly susceptible to puncture during a front-end collision. Refrigerators, in contrast, operate in an environment that features numerous internal and external ignition sources, including door light switches, automatic defrost heaters, potentially faulty wiring, gas ranges, and cigarette lighters.
In addition, flammable refrigerants differ substantially. As explained in detail in the attachment, HFC-152a and propane are both flammable, but it takes more HFC-152a to create a flammable concentration and the energy released from burning HFC-152a is significantly less than that released from burning propane. These characteristics mean that the risks from using HFC-152a are likely to be much lower than those from using HC-12a.
Thus, the 1991 risk assessment on HFC-152a in refrigerators is not relevant to the use of HC-12a in refrigerators because of the second reason, and it is not relevant to the use of HC-12a in automobiles for both reasons.
4. Flammability risk depends on the charge size
Large cars can contain twice as much refrigerant as small cars. Similarly, large US refrigerators contain much more refrigerant than small European models. A larger refrigerant charge means that a higher concentration in air is created by a given leak, and the leak will last longer. In addition, for a given volume, like the inside of a car, it is possible that a small charge would not create a flammable mixture, but a typical or larger charge could. A risk assessment must address these differences.
5. Flammability risk depends on system specifics
Even within a specific end-use, differences in design can yield differences in risk. For example, the smaller size of European refrigerators means not only that the refrigerant charge is smaller, but also that the physical size of the system is smaller, which could have an effect on where it is placed in a kitchen. Also, US refrigerators generally have automatic defrost heaters (a potential ignition source), whereas many European models do not. In cars, certain models may provide for continuous fresh air flowing through the passenger compartment, whereas others may not. A secondary loop can greatly reduce flammability risk in a supermarket refrigeration system, even though the system still falls into the retail food refrigeration end-use. Such design differences can have large impacts on overall flammability risk. Therefore, risk assessments must reflect system specifics.
6. Efficiency is not safety
EPA is aware that hydrocarbons offer potential energy efficiency gains over the use of other refrigerants. However, EPA's primary concern is the flammability of HC-12a. Papers that only discuss the system performance characteristics of HC-12a do not address this safety issue at all.
If you have any questions about this response or EPA's determinations, please contact Jeffrey Levy, the Refrigerants Analyst for the Significant New Alternatives Policy Program. Mr. Levy may be reached at (202) 233-9727.
Mary D. Nichols
for Air and Radiation