Dear Sruthi
If i remember correct: HAZMAT is a specification type which is used in context of HSM (to my knowlegde). DG is something different.
Let us try the other way around:
Anything relaetd to classic Hazardous substance management is shown here:
http://help.sap.com/erp2005_ehp_06/helpdata/en/a5/3adda043be11d188fe0000e8322f96/frameset.htm
chapter: Hazardous Substance Management (EHS-HSM) (and related subchapters)
Anything related to DG can be found in same place but chapter
"Dangerous Goods Management (EHS-DGP)"
There is one word of warning necessary. Because of history there is on the topc a further HSM tool available which should not be used any more.
Only fo completeness some reference should be given:
http://scn.sap.com/thread/1947066
VM04: data transfering from specification database to table MGEFhttps://scn.sap.com/thread/2071047
https://help.sap.com/saphelp_45b/helpdata/en/c6/f83c814afa11d182b90000e829fbfe/content.htm
Do not use the old way to handle hazardous materials !
Further hint:
Topic "DG" is related to the transport of chemicals; HSM is related in most case to "storage" of chemicals and "hanlding" of chemicals; a further link here is:
"Industrial Hygiene and Safety (EHS-IHS)" (same help.sap.com link as before). Here the context is "high level" to define which specification is handled at which work area; the tool is more relate to the "hazard" than to the "danger".
What are you looking for to get? Regarding any of the tools mentioned. there are best practise available to generate a "draft" set up.
Or is you rinterest more related to the "Component Extension"? May be check:
C.B.