Dear Wahiba
we have now two solutions for EHS IHS
EHS IHS "classic" as part of SAP ECC (e.g. Industrial Hygiene and Safety (EHS-IHS) - SAP Library)
and we habve a new solution as part of EHSM (= e.g. Risk Assessment (EHS-MGM-RAS) - Component Extension for SAP EHS Management - SAP Library)
You can not compare these solutions. Some "high level "ideas are the same but the SAP implementation is different,.
It can be assume that SAP will not enhance any more EHS IHS classic but invest only in EHSM
May be check document SAP EHS Management for Beginners
Hopefully this document might help you,
C.B.