The importation, exportation or use of controlled chemicals (including ozone-depleting chemicals such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), methyl bromide, halons, hydrobromofluorocarbons (HBFC), carbon tetrachloride, and methyl chloroform) is prohibited except under and in accordance with a valid permit issued for the relevant purpose by the Environmental Authority. (Refer to Clean Air Regulations 1993)