It is saying that a manufacturer can only use a listed substance if given an exception from the rule. And exceptions would only be given in special circumstances. The opposite is “on a routine basis” which means something that is done often and without special circumstances.

What is exception basis?

Exception Basis means a type of time reporting whereby basic regular hours are assumed by the system and only those hours that are not regular, such as overtime, are reported.

What is an exceptional offer?

1 adj You use exceptional to describe someone or something that has a particular quality, usually a good quality, to an unusually high degree., ( approval) (=extraordinary)