Heat pump the brand name Freon, a trademark of DuPont. Its manufacture is now banned or severely restricted by the Montreal Protocol of August 1987 because of the damage that CFCs cause to the ozone layer if released into the atmosphere. One widely adopted replacement refrigerant is the hydrofluorocarbon (HFC) known as R-134a (1,1,1,2-tetrafluoroethane). Heat pumps using R-134a replaced R-12 (dichlorodifluoromethane) and have similar thermodynamic properties but with insignificant ozone depletion potential and a somewhat lower global warming potential. Other substances such as liquid R-717 ammonia are widely used in large-scale systems, or occasionally the less corrosive but more flammable propane or
The Fourth Protocol (film) The Fourth Protocol (film) The Fourth Protocol is a 1987 British Cold War spy film featuring Michael Caine and Pierce Brosnan, based on the novel "The Fourth Protocol" by Frederick Forsyth. In 1968, an East-West agreement is established to halt nuclear proliferation. One of its clauses, the Fourth Protocol, forbids the non-conventional delivery of a nuclear weapon to a target. MI5 officer John Preston (Michael Caine) breaks into the residence of British government official George Berenson (Anton Rodgers) on New Year's Eve and finds a number of top secret NATO files that should not have been there. He reports his