However, because of the limitation of CFC which is dangerous to ozone layer, the studies of seeking CFC substitutes are undertaken at home and abroad.

• 但由于CFC对大气臭氧层的破坏作用，近年来其应用受到了限制，国内外都在积极寻找CFC代用品，相继出现了无氯氟代烷烃如四氟乙烷，七氟丙烷等。