hydrocar benign CFC substitutes are low-molecular-mass Arguably the most environmentally cyclopentane and isobutane. First used as refrigerants in 1867 and favored along with bons including ammonia for this purpose until CFCs were developed in the 1930s, volatile hydrocarbons are now banned from use as home refrigerants in the United States because of their flammability, but are favored in Europe and other parts of the world