An environmental pressure group claimed that Chinese factories are illegally using ozone-depleting CFCs, which have recently seen a spike in emissions that has baffled scientists. The Environmental Investigation Agency (EIA) campaign group said 18 factories in 10 Chinese provinces they looked into admitted to using banned chlorofluorocarbons. Producers and traders told EIA researchers posing as buyers that the majority of Chinese companies manufacturing foam -- in high demand as an insulator in the booming construction sector -- continue to use CFC-11 because of its better quality and lower price. CFCs are chemicals that deplete the ozone layer, the thin gaseous shield that protects life on Earth from dangerous solar rays. They were banned under the internationally binding 1987 Montreal Protocol and production of CFCs officially stopped in developing countries in 2010. Chinese authorities previously said the country successfully ended the industrial practice of using CFCs in 2007.