THE import of ozone-depleting products will be curbed under restrictions which take effect on Thursday. The rules, gazetted yesterday, forbid the import of some products from countries that are not signatories to the Montreal Protocol on ozone depletion, unless it is determined that an importing country complies with the protocol requirements. But an Environmental Protection Department spokesman said consumers may not notice the change. ''Most of the air conditioners, for example, are imported from Japan and South Korea. Those countries are already Montreal Protocol signatories,'' the spokesman said. A separate set of regulations gazetted prohibits the release into the atmosphere of refrigerants containing chlorofluorocarbons (CFCs) from vehicles' air conditioners. This means that garages servicing car air conditioners would have to capture any CFC-containing gases released. The garages also will have to keep records of the total amount of refrigerant added or removed from the air conditioners. Any increase in the cost passed along to consumers should be marginal ''as long as garages aren't using it as an excuse to rip the consumer off'', he said.