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 Rise and Fall of English Montreal The Rise and Fall of English Montreal The Rise and Fall of English Montreal is a 1993 Canadian documentary film directed by William Weintraub and produced by the National Film Board of Canada in Montreal. The film deals with exodus of English-speaking Quebecers that began in the 1960s and was accelerated by the Quebec general election, 1976. The film includes interviews with English-speaking professionals and students that are preparing to leave Montreal, joining an exodus of 300,000 anglophones that left the province in the last two decades. This exodus is reflected in over 100 English-speaking schools that have closed in