In 1994, four years after the enactment of the Clean Air Act Amendments, the Environmental Protection Agency issued its first list of allowable substitutes for CFC and HCFC refrigerants. The EPA and its program, known as the Significant New Alternatives P olicy (SNAP) program, regularly evaluates new and existing products in eight sectors that are historically known to produce the highest volume of ozone-depleting substances.

Effective May 23, 2001, the EPA's latest list for the refrigeration and air-c onditioning sector includes 13 alternatives to CFCs and HCFCs for both new and retrofit equipment. All of these refrigerants have varying capacities to increase global warming; this measurement is called the refrigerant's Global Warming Potential (GWP). It is measured by comparing a given mass of chemical to the same mass of carbon dioxide over a 100-year time period. Each description of the alternatives below includes its flammability potential, toxicity and recommended exposure data.

HFC - 134a/HBr (92/8)

Uses and Industries Affected: A blend of 92 percent HFC-134a and 8 percent hydrogen bromide (HBr), by weight. Used as a primary heat transfer fluid in new secondary loop or not-in-kind replacements. Components of the blend are also known as 1,1,1,2-tetrafluoroethane for HFC-134a and hydrogen bromide for HBr.

Substitute for: CFC-12 and R-502 in cold storage warehouses and refrigerated transport; CFC-11, CFC-12, CFC-114, CFC-115 and R-502 in new industrial process refrigeration.

Environmental: Has the potential to deplete ozone but is less than 0.02. Two to seven-day atmospheric lifetime. GWP of HBr is very low; for HFC-134a, it is 1,600. For volatile compounds, HFC-134a is exempt from CAA regulations but HBr is not.

Flammability Information: Neither chemical for this blend is flammable.

Toxicity and Exposure Data: OSHA's permissible exposure limit (PEL) for HBr, over an eight-hour period, is 3 ppm. The American Council of Governmental Industrial Hygienists (AGGIH) also recommends an exposure limit of 3 ppm. For HFC-134a, the EPA supports a workplace environmental exposure level (WEEL) from the American Industrial Hygiene Associ-ation (AIHA) of 1,000 ppm.

PFC-330ST, PFC-550HC, PFC-660HC, PFC-1100HC, PFC-1100LT, PGC-100, PGC-150, PFC-331ST, PFC-551HC, PFC-661HC, PFC-1101HC, PGC-151

These 12 blends all have similar environmental data and exposure limits. Except where noted differently, the blends will have the qualities noted.

Uses and Industries Affected: For use in new or retrofit systems.

Substitute For: CFC-13, CFC-113, CFC-114 and their blends in very low temperature refrigeration.

Environmental Information: Do not have a zero reading for ozone depletion potential (ODP), so will deplete ozone if vented. Some of these blends have not been exempted for VOCs under the Clean Air Act. GWP for some of the blends is very high, but the values are lower than the refrigerants they are replacing.

Flammability Information: All blends except for PGC-100, PGC-150 and PGC-151 are flammable in accordance with ASTM E-681-85. Risk is limited, however, due to the small charge used with these blends. Training is recommended to further reduce risk.

Toxicity And Exposure Data: Exposure guideline for all components is 1,000 ppm over an eight-hour time-weighted average. MSDS manufacturer acceptable exposure limit (AEL) recommendations for these blends are 30 ppm.

Choices and Consequences

As with all refrigerants, observe and enforce the MSDS safety and handling instructions. Implement me-chanical room safety measures as outlined in ASHRAE Standard 15 (1994), which include installation of refrigerant-specific monitors, sensor-activated exhaust systems and makeup air fans, and placing refrigerant relief lines so they vent to the outdoors.

EPA strongly encourages professionals to use the alternatives as recommended. Technicians should handle all refrigerants with great care. Minimize a refrigerant's environmental impact by practicing proper recovery and recycling procedures. Some of the new blended refrigerant alternatives may fractionate, or leak disproportionately, and need to be disposed of instead of recharged into a system. These new waste streams of useless blended refrigerants can create an extra burden when keeping records for used refrigerant disposal. Check with your refrigerant supplier to find out what provisions they have for used refrigerant disposal, especially for blends that can no longer be used in a system. Find out up front what the disposal costs are, if any, before making a final decision on a retrofit or replacement project that involves an alternative blend refrigerant.