Even so, the U.S. Environmental Protection Agency (EPA) document 40 CFR Part 82, titled “Protection of Stratospheric Ozone: Listing of Substitutes for Ozone-Depleting Substances — Hydrocarbon Refrigerants,” officially gave Significant New Alternatives Policy (SNAP) approval to R-290 (propane), R-600a (isobutene), and R-441A (a blend marketed by ComStar International as HCR 188c).
The approval initially comes with some limitations. These include charge sizes to 57 grams for household appliances, and 150 grams for commercial units and only for equipment specially designed for the approved HCs with ignition sources minimized and with no retrofitting allowed. EPA also requires warnings and labels to make those working on the equipment aware that the system contains a potentially flammable gas in the refrigeration system.