To protect the stratospheric ozone layer, international agreements have been reached to ban the use and trade of the ozone-destroying chemicals called chlorofluorocarbons (CFC’s). In order to replace these chemicals with others that are more benign, the equipment in which they are used – like freezers, coolers, and units for foam plastic production – must be substituted for new ones.
原因很简单。为了保护平流层臭氧层，国际上已经达成一致，禁止买卖和使用破坏臭氧的化学剂：氯氟碳（CFC’s）。为了能够用其他更为温和的化学剂代替它，使用氯氟碳所需的设备——诸如冷冻器、冷却器和泡沫塑料生产单位——也必须以新换旧。