Dear Rajiv,
ESIC deduction is a mandatory deduction for all employees whose gross is below 15001 Rs. But there are certain industries and certain locations where ESIC is not applicable. Please find attached the details. Also refer google and CITEHR for more details.
I have collected all these documents from CITEHR itself, posted by various members like you and me. Thanks a lot to CITEHR and its member. Also if you have any further queries, please let me know.