Air conditioning eventually reach the upper atmosphere. Once the refrigerant reaches the stratosphere, UV radiation from the Sun homolytically cleaves the chlorine-carbon bond, yielding a chlorine radical. These chlorine radicals catalyze the breakdown of ozone into diatomic oxygen, depleting the ozone layer that shields the Earth's surface from strong UV radiation. Each chlorine radical remains active as a catalyst until it binds with another radical, forming a stable molecule and quenching the chain reaction. Prior to 1994, most automotive air conditioning systems used R-12 as a refrigerant. It was replaced with R-134a refrigerant, which has no ozone depletion potential. Old R-12 systems
History of the Berlin S-Bahn that were left opened after the strike do include: The 1980 incidents turned media and political attention toward what was left of West Berlin's S-Bahn network. The city government decided to enter negotiations with East Germany, which were finally successful. By contrast, during the same period, services on the S-Bahn in East Berlin were increased and new lines built as housing projects expanded eastward from the city centre. With most of the U-Bahn located in West Berlin, the S-Bahn became the backbone of the East Berlin transit network. The DR has purchased DR Class 270 as a result, where it