The EPA approved the use of R-290 (propane), R-600a (isobutene), and an HC-blend known as R-441A for charge sizes up to 57 grams for household appliances and 150 grams for commercial units. The move was considered significant in opening the doors for so-called natural refrigerants where chemically produced f-gas refrigerants had long held domain.
The use of HCs got the support of such end-user powerhouses as Ben and Jerry’s and General Electric. And that, combined with Coca-Cola increasing its advocacy of another natural refrigerant, R-744 (CO2), and developments in which ammonia is used in commercial sites such as supermarkets, created the recent shift of interest in naturals.