Forane® 141b is a liquid blowing agent ideal for spray foam applications. Since it is a liquid at atmospheric conditions and has low vapor thermal conductivity, which allow the production of polyurethane foam with excellent physical properties. The low vapor thermal conductivity of Forane® 141b makes it ideal for the appliance market. Forane® 141b is an ideal blowing agent for polyurethane core metal-faced panels used for construction. R-141b is an HCFC and, as an ozone depleting substance, is subject to phase out according to the Montreal Protocol international treaty and the Clean Air Act in the United States; it has been phased out in the United States for use in foam.